Details of a Researcher - Kohiyama, Masayuki

Papers - Kohiyama, Masayuki

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Accuracy Improvement of Damage Classifier for a Wooden Building Considering Pulse-like Seismic Ground Motions

MIZOBUCHI Rikuto, KOHIYAMA Masayuki, and YAMASHITA Takuzo

Journal of Japan Association for Earthquake Engineering (Japan Association for Earthquake Engineering) 25 ( 4 ) 97 - 108 2025.03

Research paper (scientific journal), Accepted, ISSN 1884-6246

Rapid damage assessment by a structural health monitoring system is expected to prevent casualties caused by the collapse of wooden buildings due to repeated seismic motions. While neural networks are known to be a powerful tool for determining the risk of collapse based on the response records, they are not good at classifying untrained damage patterns. This study proposed a method to consider the diversity of damage patterns in the construction of a damage classifier for wooden buildings. This is achieved by using pulse-like simulated ground motions as the input ground motions for seismic response simulation of a target building model in the development of the training dataset. The effectiveness of the proposed method was validated by comparing its accuracy on test data.

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Damage Classifier for Wooden Buildings Based on Hysteresis Loop Images Using CNN

Chiba, S., Kohiyama, M., and Yamashita, T.

Proc. of the 18th World Conference on Earthquake Engineering 2024 (WCEE2024) 2024.06

Research paper (international conference proceedings), Joint Work, Accepted

Structural health monitoring (SHM), which evaluates building damage based on seismic response data, is useful for rapidly assessing damage due to earthquakes. If a reliable damage assessment system for houses can be developed, the loss of human lives caused by the aftershocks of major earthquakes can be reduced. When a target building is damaged by strong seismic ground motions, the shape of the restoring force–story drift angle curve (hysteresis loop) changes. Therefore, based on the hysteresis loop images of wooden buildings, this study proposes a method to classify the risk of collapse because of future seismic ground motions using a convolutional neural network (CNN). To develop training data, structural response analysis is conducted using “wallstat”, which is a numerical analysis software for wooden structures. SHM has more severe consequences when it misclassifies an unsafe condition as safe (miss) than when it misclassifies a safe one as unsafe (false alarm). Therefore, we propose the usage of a dataset that does not contain safe model data near the threshold value of major damage for training to decrease the possibility of misses, and we verify the effect of this. In creating the hysteresis loop images, we examine the range of the axes using two methods: fixing it at specific values and matching it to the range of the minimum and maximum values. The investigation results suggest that the trained CNN learns the changes in structural characteristics, such as stiffness reduction, damping increase, and residual displacement.

A Warm Standby Based on the Probability to Exceed Damage Threshold for Seismic Response of a Server

Yusuke KIDA, Enon HIRAOKA, Masayuki KOHIYAMA

Journal of Social Safety Science (Institute of Social Safety Science) ( 43 ) 19 - 27 2023.11

Research paper (scientific journal), Joint Work, Last author, Accepted, ISSN 1345-2088

This study proposes a new warm standby method for computer servers based on seismic response. The proposed method triggers a warm standby in the case that the exceedance probability of the safety limit of seismic response predicted by the last two-second observation record exceeds a preset threshold. Numerical simulations showed that the proposed method reduced the loss cost by 1.64% compared to conventional methods. To validate this method, we conducted shaking table tests. When a simulated earthquake motion was input, the loss cost was reduced by 60.6%. However, when observed records were input, the loss cost was increased by 3.89%. The results suggest that it is necessary improve the input ground motion model.

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Development of Tool to Enable Autonomous In-Person and Remote Tabletop Exercises by Residents for Developing Next-Generation Leaders for Volcanic Disaster Reduction

Masayuki KOHIYAMA, Honoka TAKASHIMA, Masayasu YAMAUCHI, Mitsuhiro YOSHIMOTO, Tomohiro KUBO

Journal of Social Safety Science (Institute of Social Safety Science) ( 43 ) 315 - 325 2023.11

Research paper (scientific journal), Joint Work, Lead author, Corresponding author, Accepted, ISSN 1345-2088

To reduce volcanic disasters, it is important for residents to practice mutual support under the leadership of voluntary disaster reduction groups. However, many communities lack the human resource for their future leaders. To address this issue, we proposed a digital tool for residents to develop leaders by themselves. The system requirements were determined to enable residents to conduct autonomous and effective tabletop exercise in both in-person and remote formats. The usefulness of the tool was confirmed through workshops with residents of the areas at the foot of Mt. Fuji.

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Study on a Simplified Model of a High-Rise Shear-Type Building for Evaluation of Q-Δ Resonance

Anamizu R., Kohiyama M.

Japan Architectural Review (Wiley) 6 ( 1 ) 1 - 16 2023.10

Research paper (scientific journal), Joint Work, Last author, Corresponding author, Accepted, ISSN 2475-8876

To evaluate Q–Δ resonance, which is a torsional resonance phenomenon caused by geometric nonlinearity, a simplified model for a multistory non-eccentric building with a shear-type structure was proposed. A four-story small-scale specimen was designed and fabricated, assuming a non-eccentric steel structure with a height of 324 m, and conducted shaking table tests of the specimen. Q–Δ resonance was confirmed as predicted by the simplified model. In addition, the simplified model reproduced the resonance amplitude calculated using a finite element model of the specimen with constrained out-of-plane slab rotation. The simplified model can be used to predict the Q–Δ resonance response when the bending deformation of an entire building is very small.

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Probability Distribution of Torsional Response by Q–Δ Resonance of Multi-Story Building under Long-Period Seismic Motion

Kohiyama M.

Proceedings of the 14th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP14) 2023.07

Research paper (international conference proceedings), Single Work, Lead author, Corresponding author, Accepted

When the torsional moment owing to geometric nonlinearity synchronizes with the torsional mode response, an internal resonance phenomenon occurs in a building structure system. The author’s research group calls this phenomenon Q–Δ resonance. The probability distribution of the torsional response was evaluated using Monte Carlo simulations on a 60-story building model, the input wave being simulated using nonstationary colored-noise ground motion. The results showed that the torsional response greatly increased the horizontal acceleration response and the response amplification ratio between the center and corner of the top floor could exceed 1.2 when the model satisfied the Q–Δ resonance condition that the natural frequency of the torsional second mode matched the sum of the first natural frequencies in the x- and y-directions. It was also evident that closer proximity to the resonance condition increased the amplification ratio. These results suggest that Q–Δ resonance may need to be considered in seismic design.

BAYESIAN UPDATING OF WOODEN STRUCTURAL PARAMETERS AND SEISMIC DAMAGE CLASSIFIER USING NEURAL NETWORK

Mizobuchi R., Kohiyama M., Yamashita T.

Proceedings of the 9th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2023) 1 2335 - 2347 2023.06

Research paper (international conference proceedings), Joint Work, Accepted, ISSN 26233347

Structural health monitoring is an effective way to quickly and efficiently detect earthquake damage to a building. However, its applications to wooden buildings are still limited. One of the challenges in predicting the seismic response of a wooden structure is that the effect of variance in its material and structural properties is relatively significant. To handle this problem, we propose a method to update the damage classifier using Bayesian system identification. The damage classifier is constructed using neural network (NN) and machine learning techniques. The method utilizes the weighted loss function for the NN to reflect the updated probability distribution of the structural parameters. The NN is tuned using backpropagation, where the training data are consequently weighed by the weighed loss function, directly using the value of the posterior probability, according to the data obtained from the numerical model of a target structure with the corresponding parameters. Using the result of the Bayesian updating, the tuned NN damage classifier achieved a higher accuracy than before tuning by reflecting the posterior probability distribution of the structural parameters.

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THREE-DIMENSIONAL FRAME ANALYSIS OF Q-Δ RESONANCE OF CENTER-CORE BIAXIALLY SYMMETRICAL HIGH-RISE BUILDING UNDER LONG-PERIOD EARTHQUAKE MOTION

Kohiyama M., Maki S.

Proceedings of the 9th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2023) 1 961 - 970 2023.06

Research paper (international conference proceedings), Joint Work, Lead author, Accepted, ISSN 26233347

When large displacements occur in buildings with different stiffnesses in the two horizontal directions, torsional moments are generated owing to geometric nonlinearities. Consequently, when the sum or difference of the translational mode natural frequencies in the two horizontal directions is close to the torsional mode natural frequency, the torsional mode is excited. This is known as Q-Delta resonance. Therefore, we created a three-dimensional frame model of a center-core high-rise building with a biaxially symmetrical plane that satisfied the Q-Delta resonance condition and examined whether the torsional response was excited by long-period design waves. A time-history response analysis was conducted assuming elastic response and considering geometric nonlinearities. It was confirmed that the torsional mode could be induced.

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EXPERIMENT AND SIMULATION OF Q-Δ RESONANCE USING FOUR-LAYER BENDING-SHEAR TYPE SPECIMEN

Kai R., Kohiyama M.

Proceedings of the 9th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2023) 1 971 - 981 2023.06

Research paper (international conference proceedings), Joint Work, Last author, Accepted, ISSN 26233347

Torsional vibration of buildings subjected to earthquake motion has been studied for many years, but the torsional vibration of high-rise buildings has not yet been clarified. Many previous studies have focused on eccentricity, the mismatch between the center of gravity and the rigid center, as the cause of torsional vibration. However, in buildings with no eccentricity, torsional vibrations could be observed. The authors' research group focused on the “Q-Delta effect,” a phenomenon in which torsional torque is generated due to geometric nonlinearity and “Q-Delta resonance,” a phenomenon in which resonance occurs when the period of torsional torque generation coincides with the natural period of the torsional mode. In order to analyze the characteristics of Q-Delta resonance, a small-scale specimen was designed and fabricated from an 81-story high-rise building with biaxially symmetrical plans, which was reduced to four stories. As a result, the torsional response of the experimental and simulation results generally agreed, confirming that the torsional response increases when the Q-Delta resonance condition is satisfied. In addition, a comparison of the torsional response with a specimen with a smaller tower ratio and less bending deformation was conducted, and it was confirmed that the peak of the torsional response was steeper in the present study case.

Study on A Simplified Model of a High-Rise Shear-Type Building for Evaluation of Q–Δ Resonance

Anamizu R., Kohiyama M.

Journal of Structural and Construction Engineering (Architectural Institute of Japan) 88 ( 803 ) 59 - 70 2023.01

Research paper (scientific journal), Joint Work, Accepted, ISSN 13404202

To evaluate Q–Δ resonance, which is a torsional resonance phenomenon caused by geometric non-linearity, we proposed a simplified model for an n-story non-eccentric building model with a shear-type structure. We designed and fabricated a four-story small-scale specimen assuming a non-eccentric steel structure with a height of 324 m, and conducted shaking table tests. As a result, the occurrence of Q–Δ resonance was confirmed as predicted by the simplified model. In addition, the simplified model reproduced the resonance amplitude in a finite element model of the specimen with the out-of-plane rotation of slabs constrained and its validity was confirmed.

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Torsional behavior of a non-eccentric structure considering the effect of shear deformations in vertical members

Maki S., Kohiyama M.

Japan Architectural Review (Wiley) 5 ( 4 ) 404 - 431 2022.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 2475-8876

Torsional moments can occur in a column owing to the geometric nonlinearity when the top of the column undergoes a large displacement in two horizontal directions. Periodically generated torsional moments can excite the torsional mode of a building owing to the internal resonance. For high-rise buildings, there is a risk that long-period seismic motions can cause a non-negligible torsional response due to this phenomenon. To investigate this risk, this study focuses on non-eccentric single-story and two-story shear-type structural models with an aggregate column, which is assumed to be an elastic Timoshenko beam. We derived the equations of motion for the models under horizontal ground motions and confirmed that the equations were identical to those of the models with an aggregate column of an elastic Euler beam. We then performed time-history response analyses of the models satisfying the internal resonance conditions under the input ground motions of harmonic waves, Gaussian white noise acceleration, acceleration records of previous earthquakes, and a long-period design wave. The results showed that the maximum horizontal acceleration at the corner of the top floor slab could be increased by more than 60% of the acceleration at the center of the slab in the worst case.

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Fundamental Study of Q–Δ Resonance Considering Higher-Order Modes by Shaking Table Experiments and Finite Element Analysis

Ryosuke ANAMIZU, Masayuki KOHIYAMA

Journal of Structural Engineering (Architectural Institute of Japan) 68B 386 - 396 2022.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 0910-8033

The Q–Δ effect is a phenomenon that a column with different lateral stiffness generates a restoring torsional moment owing to geometric nonlinearity when its top displaces in two horizontal directions simultaneously. The Q–Δ resonance that is resonance of a torsional mode induced by the periodic torsional moment due to the Q–Δ effect could cause considerable torsional vibration even in non-eccentric buildings. However, the Q–Δ resonance in higher-order modes has not been investigated well. We first constructed a model of a two-story non-eccentricity structure and derived the conditions of the Q–Δ resonance considering higher-order modes. Then, we conducted shaking table experiments and finite element analysis to reproduce the experiments. As a result, it was confirmed that the second mode in the torsional direction was excited as predicted by the derived Q–Δ resonance condition. Moreover, the finite element analysis could reproduce the experimental result with high accuracy.

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Torsional response of a bisymmetric structure induced by bending–torsion interaction in vertical members

Kohiyama M., Yokoyama H., Maki S.

Japan Architectural Review (Wiley) 5 ( 1 ) 3 - 19 2022.01

Research paper (scientific journal), Joint Work, Lead author, Last author, Corresponding author, Accepted

The biaxially symmetric column induces torsional moment owing to the bending–torsion interaction when the top of the column is given horizontal displacement in the two directions of the principal axes of the cross section and the rotation of the column ends around the axes is constrained. Hence, horizontal ground motions in two directions can cause non-negligible torsional vibration in a high-rise building owing to autoparametric resonance. To investigate this phenomenon, in this study, we focus on a single-story structure with an aggregated column, which is a model for columns or core structures in tall buildings and is assumed to be an elastic Euler beam; subsequently we derive the equations of motion under horizontal ground motions in two directions. The resonance condition in the torsional direction is also investigated. Time-series response analyses are performed for input ground motions of harmonic waves, white noise, acceleration records of prior earthquakes, and a long-period design wave, and the relationship between the ratio of two translational natural frequencies and the increase in maximum responses is explained. The results demonstrate that the absolute acceleration response to the long-period design wave could increase by more than 50% in the worst-case scenario.

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火山災害対応における認知バイアスを克服するための訓練ツール

Yuzo KONNO, Honoka TAKASHIMA, Masayuki KOHIYAMA, Mitsuhiro YOSHIMOTO, Tomohiro KUBO

Journal of Social Safety Science (Institute of Social Safety Science) ( 39 ) 233 - 243 2021.11

Research paper (scientific journal), Joint Work, Accepted, ISSN 1345-2088

In recent disasters, there have been many cases that people failed to escape despite evacuation advisories or did not make appropriate preparations in advance. One of the possible causes is the influence of cognitive bias. However, countermeasures against cognitive bias have not been developed in community disaster management. In this study, we developed a training tool in the form of web application software to overcome cognitive bias by acquiring knowledge about possible cognitive bias in response to volcanic disasters and discussing countermeasures with community members. The effectiveness of the tool was verified in workshops held in Fujiyoshida City. This training tool allows residents to conduct training on their own using a video conferencing system.

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Experiment of torsional response induced by the Q–delta resonance

Mizutori F., Kohiyama M.

The Structural Design of Tall and Special Buildings (Wiley) 30 ( 4 ) 2021.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 15417794

Because of geometric nonlinearities, vibrations in two horizontal directions can generate a torsional moment that induces a torsional response, even in a structure with no eccentricity; we term this phenomenon Q–Δ effect. In this study, the torsional response caused by the Q–Δ resonance was investigated by performing a shaking table test that involves a single-layer symmetric specimen. The specimen was designed and fabricated by focusing on one of two resonance conditions. Its moment of inertia was adjustable by changing locations of weights, and the natural frequency in the torsional mode could be modified. We developed a numerical model of the specimen, in which the columns connected to the slab were integrated into an elastic Euler beam. It was confirmed that the torsional response increased near the predicted Q–Δ resonance point. In addition, the acceleration at the corner of the slab was significantly increased. The formulated equations of motion provided a better prediction of the actual phenomena. Because the specimen corresponds to a stiff and slender high-rise building when converted into a full scale, the result suggests a need to be aware of the risk of torsional response increase due to the Q–Δ resonance.

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Deep neural network for detecting earthquake damage to brace members installed in a steel frame

Yamashita, T., Kohiyama, M., Oka, K.

Japan Architectural Review (Wiley) 4 ( 1 ) 56 - 64 2021.01

Research paper (scientific journal), Joint Work, Accepted

We are developing an artificial intelligence system for structural health monitoring that can detect local damage in a building structure by using the E‐Simulator numerical simulation system that is being developed by the Japanese National Research Institute for Earth Science and Disaster Resilience. In this study, we confirmed the applicability of a multiclass classifier using a deep neural network to address the problem of identifying damage patterns in braces installed in a steel frame. Experimental data obtained from shaking table tests were used for training and testing. Cross-validation tests were conducted for several cases with different numbers of sensors, sensor degrees of freedom, and nodes in the hidden layers of the network. The results demonstrated that the accuracy of the damage pattern detection from the constructed classifier exceeded 77% when the appropriate hidden layers were selected and reached 87.9% for the best case.

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Volcanic Hazard Map of Mt. Fuji Using Augmented Reality

Masayuki KOHIYAMA, Tatsumi AKAHORI, Mitsuhiro YOSHIMOTO, Tomohiro KUBO

Journal of Social Safety Science (Institute of Social Safety Science) ( 37 ) 147 - 155 2020.11

Research paper (scientific journal), Joint Work, Accepted, ISSN 1345-2088

The volcanic hazard map is one of the effective proactive measures for volcanic disasters. However, the general public has little interest in the hazard maps because it is not easy to understand them. To address this problem, this study develops a volcanic hazard map using augmented reality (AR). The effectiveness of the proposed AR hazard map was verified through the workshops held in Fujiyoshida City, in which participants actually used the prototype map. As a result, it was clarified that the AR hazard map could effectively supplement a printed hazard map and it was also found that the display switching function of the hazards was particularly effective for promoting understanding.

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A Framework of Disaster Imagination Game by Residents for Developing Next-Generation Leaders for Volcanic Disaster Reduction

Honoka TAKASHIMA, Masayuki KOHIYAMA, Mitsuhiro YOSHIMOTO, Tomohiro KUBO

Journal of Social Safety Science (Institute of Social Safety Science) ( 37 ) 175 - 185 2020.11

Research paper (scientific journal), Joint Work, Accepted, ISSN 1345-2088

In order to reduce volcanic disasters, it is important for residents to practice mutual assistance, which can be led by a voluntary disaster reduction group. However, many communities lack the human resources for their future leaders. To address this issue, we created a framework of disaster imagination game to develop next-generation leaders. The effectiveness of the game was verified through workshops held in Fujiyoshida City. The framework allows residents to train independently by using a web application software.

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Detection method of unlearned pattern using support vector machine in damage classification based on deep neural network

Kohiyama M., Oka K., Yamashita T.

Structural Control and Health Monitoring (Wiley) 27 ( 8 ) 2020.08

Research paper (scientific journal), Joint Work, Lead author, Last author, Corresponding author, Accepted, ISSN 15452255

Deep neural networks (DNNs) are a powerful tool for structural health monitoring because they can automatically identify features that are useful for classifying and recognizing damage patterns of a target structure with high accuracy. However, it can misclassify input data of an unlearned damage pattern as any of the learned damage patterns. To address this shortcoming, this paper presents a method to detect unlearned damage patterns by using the collective decision of support vector machines (SVMs). SVMs are constructed using feature vectors from training data, which are stored in the output layer of a DNN. To validate the proposed method, we used two different datasets, one containing experimental data of a steel frame structure and the other containing simulated and experimental data of a wooden house. In both cases, it correctly identified data of both learned and unlearned damage patterns. The proposed method can enhance the effectiveness of structural health monitoring (SHM). In addition, because it does not employ SHM-specific characteristics, it can be used in various pattern recognition applications, such as image and audio processing.

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Seismic Response Control of an Instrument With Casters Using Computer Vision Based on Reinforced Learning of Dynamic Analysis Results Considering Friction

Kento WAKABAYASHI, Yosuke KAWANISHI, Masayuki KOHIYAMA, Ryo EGUCHI, and Masaki TAKAHASHI

Journal of Structural Engineering (Architectural Institute of Japan) 66B 305 - 314 2020.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 0910-8033

We developed a computer vision system to control the seismic response of medical equipment with casters in a building subjected to earthquake excitation. The controller employs a neural network and the reinforced learning was conducted based on dynamic simulations of a controlled equipment under building floor motion. In the dynamic simulations, we used Open Dynamics Engine, which is a simulator library of three-dimensional rigid body dynamics, and we introduced a friction model to simulate the dynamic behavior of the casters. To validate the proposed system, we conducted shaking table tests and it was confirmed that the proposed control could successfully suppress the response of the equipment.

Semi-actively Implemented Non-linear Damping for Building Isolation Under Seismic Loadings

Zhu Y.P., Lang Z.Q., Kawanishi Y., Kohiyama M.

Frontiers in Built Environment (Frontiers) 6 2020.02

Research paper (scientific journal), Joint Work

It is well-known that semi-active solution can achieve building isolation with much less energy requirements than active solutions. Also, it has been shown in previous studies that compared to linear damping, non-linear damping performs better for building isolation under sinusoidal ground motions. The present study is concerned with the extension of the application of the semi-actively implemented non-linear damping to building isolation under seismic loadings. A two-degree-of-freedom (2-DOF) scaled building model is used for simulation studies. Experimental tests on a physical building model have been used to validate the effectiveness of the 2-DOF scaled building model in representing the behaviors of a physical building structure. The optimal design of the semi-actively implemented non-linear damping for building isolation under design seismic motions is then carried out using the 2-DOF scaled building model based on simulation studies. The results show that an optimal design of semi-actively implemented non-linear damping can improve the performance of building isolation under design seismic motions in terms of both absolute acceleration and inter-story drift.

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Detection of Unlearned-Damage-Pattern Data Based on k-Nearest Neighbors Algorithm and Welch’s t Test in Damage Classification Using Deep Neural Network

Masayuki KOHIYAMA, Motoki FUTEMMA, Kazuya OKA, and Takuzo YAMASHITA

Proceedings of the Ninth Japan Conference on Structural Safety and Reliability (The Society of Materials Science, Japan) 319 - 326 2019.10

Research paper (other academic), Joint Work, Accepted

Deep neural network has been applied to damage classification in structural health monitoring. However, it has a drawback that it classifies data of an unlearned pattern as any of learned patterns. We propose a method to detect unlearned-damage-pattern data based on k-nearest neighbors algorithm and Welch’s t test. As input data of neural network, we used acceleration records acquired in shaking table test using steel frame specimen, which is a 1/3-scale model of a four-story steel structure and imitates structural damage with relaxed braces. The records were divided into one-second-long samples and used for training and verifying neural network. We extracted feature data in an output layer of the network and clarified that the data do not follow to a Gaussian distribution. Therefore, Anomaly index based on k-nearest neighbors algorithm is introduced to measure the non-similarity to learned pattern data. Using data of shaking table test of a steel frame structure, we verified that unlearned-damage-pattern data can be detected by Welch's t test.

Probability Distribution of Torsional Response Induced by Lateral Displacement and Inertial Force

Hiroki Yokoyama and Masayuki Kohiyama

Proceedings of the 29th European Safety and Reliability Conference, ESREL 2019 (Research Publishing, Singapore) 3224 - 3231 2019.09

Research paper (international conference proceedings), Joint Work, Accepted

In previous studies of torsional response, researchers considered that torsional vibration of building is caused by eccentric distribution of stiffness, damping, and mass of a structure, or spatially non-uniform ground motion input to a long or large base mat of a structure. However, we have discovered that the torque generated by horizontal displacement and perpendicular inertial force, which we call the Q–Delta effect, can cause torsional vibration. In order to investigate this effect, we considered a single finite-size mass-linear elastic shear and torsion spring model and derived the resonance condition with respect to a torsional response from the equation of motion. In this study, we discuss probability distribution of the induced torque and torsional displacement response to uncorrelated Gaussian white noise input ground acceleration in two translational directions. In the frequency domain, the power spectral density function of the torque induced by the Q–Delta effect is proportional to a convolution of two frequency response functions in two translational directions. In the time domain, the probability density function of the induced torque is the modified Bessel function of the second kind. Time-history response analysis was conducted to verify these theoretical results and to investigate the distribution of torsional response to Gaussian white noise input ground acceleration.

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Haruka Yokoyama, Hajime Iwai, and Masayuki Kohiyama

Proceedings of the 29th European Safety and Reliability Conference, ESREL 2019 (Research Publishing, Singapore) 3217 - 3223 2019.09

Research paper (international conference proceedings), Joint Work, Accepted

We propose a quantitative phase model to predict element waves of adjacent element faults to simulate ground motion using the stochastic Green's function method. We paired seismic records under the specified conditions of near-identical magnitude and hypocenter depth. To model the acceleration waveform similarities of the seismic record pair, a relationship between the mean value of Fourier amplitudes and an absolute value of Fourier phase difference was represented using a beta distribution. We then derived a regression formula of beta-distribution shape parameters with respect to the distance between the two hypocenters of each pair. Based on the proposed model, a seismic wave was synthesized, along with a calculated RMS error in acceleration response spectra between the synthesized wave and the observed record of the 2016 Kumamoto earthquake. It was confirmed that the proposed model decreased the error successfully.

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Update of control parameters for semi-actively controlled base-isolated building to improve seismic performance

Masayuki Kohiyama, Masashi Omura, Masaki Takahashi, Osamu Yoshida, and Koichi Nakatsuka

Japan Architectural Review (Wiley) 2 ( 3 ) 226 - 237 2019.07

Research paper (scientific journal), Joint Work, Accepted, ISSN 2475-8876

The Sosokan building of Keio University located in Yokohama, Japan, is a base‐isolated building with a semi‐active control system. The semi‐active dampers’ damping coefficient is changed to best reproduce the optimal control force in linear‐quadratic‐gaussian control. However, the implemented control gain was calculated on the basis of the structural parameters applied at the design stage. In this study, we identified the building's actual structural parameters using observational records from the 2011 Tohoku earthquake. Using the updated structural model and 1000 simulated ground motions, we conducted a dynamic response analysis, which resulted in a fragility curve. Then, we evaluated the damage probability using the fragility curve and a seismic hazard curve. Finally, we determined the optimal control parameters to minimize the damage probability and used these parameters to implement the semi‐active control system.

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Design Method of Inter-Story Tuned Mass Damper to Reduce Story Deformation and Its Verification Tests

Masayuki KOHIYAMA and Masashi OMURA

Journal of Structural Engineering (Architectural Institute of Japan) 65B 77 - 84 2019.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 09108033

An inter-story tuned mass damper (ISTMD) is a variant form of a tuned mass damper, which is placed between consecutive floors to suppress the resonant response of a structure. We derived design parameters of an ISTMD under ground excitation that minimize story deformation on the basis of the fixed-points theory. Then, a shaking table tests were conducted to investigate the performance of an ISTMD with derived parameters. The result showed that the ISTMD worked well to suppress the response around the resonance point and it reduced the displacement and maximum acceleration responses more effectively than an ordinary damper when the El Centro wave was input to the specimen.

Torsional Response Induced by Lateral Displacement and Inertial Force

Masayuki Kohiyama and Hiroki Yokoyama

Frontier in Built Environment (Frontiers) 4 ( 38 ) 1 - 12 2018.07

Research paper (scientific journal), Joint Work, Accepted, ISSN 2297-3362

Eccentric distribution of stiffness, damping, and mass of a structure, and spatially non-uniform ground motion input to a long or large base mat of a structure are well-known causes of torsional response. We have discovered that the torque generated by horizontal displacement and perpendicular inertial force, which we call the Q-Δ effect, can be a cause of torsional response. We formulated the equation of motion of a single finite-size mass-linear elastic shear and torsion spring model and clarified the resonance condition of the torsional response to sinusoidal ground acceleration. Time-history response analysis verified that the torsional response forms beat and the maximum torsional response of the simulation result agrees with that theoretically predicted. Further time-history response analysis conducted of white noise ground acceleration showed that even one-directional white noise ground acceleration can induce torsional response in a linear elastic system without any structural eccentricity.

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Update of Control Parameters of Semi-Actively Controlled Base-Isolated Building

Kohiyama, M., Omura, M., Takahashi, M., Yoshida, O., and Nakatsuka, K.

Proc. 7th World Conference on Structural Control and Monitoring 351 - 359 2018.07

Research paper (international conference proceedings), Joint Work, Accepted

The Sosokan university building has base isolation and a semi-active control system. The semi-active dampers’ damping coefficient is changed so as to best reproduce the optimal control force in linear-quadratic-Gaussian control. However, the implemented control gain was calculated based on the structural parameters at the design stage. In this study, we identify the building’s actual structural parameters by using observation records of the 2011 Tohoku earthquake. Dynamic response analysis is conducted by using the updated structural model and 1000 simulated ground motions. Then, the damage probability is evaluated using a fragility curve derived from the result of dynamic response analysis as well as a seismic hazard curve. Finally, the optimal control parameters are obtained to minimize the damage probability, and these parameters are implemented in the semi-active control system.

Nonlinear damping based semi-active building isolation system

Carmen Ho, Yunpeng Zhu, Zi-Qiang Lang, Stephen A. Billings, Masayuki Kohiyama, and Shizuka Wakayama

Journal of Sound and Vibration (Fuji Technology Press) 424 302 - 317 2018.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 0022460X

Many buildings in Japan currently have a base-isolation system with a low stiffness that is designed to shift the natural frequency of the building below the frequencies of the ground motion due to earthquakes. However, the ground motion observed during the 2011 Tohoku earthquake contained strong long-period waves that lasted for a record length of three minutes. To provide a novel and better solution against the long-period waves while maintaining the performance of the standard isolation range, the exploitation of the characteristics of nonlinear damping is proposed in this paper. This is motivated by previous studies of the authors, which have demonstrated that nonlinear damping can achieve desired performance over both low and high frequency regions and the optimal nonlinear damping force can be realized by closed loop controlled semi-active dampers. Simulation results have shown strong vibration isolation performance on a building model with identified parameters and have indicated that nonlinear damping can achieve low acceleration transmissibilities round the structural natural frequency as well as the higher ground motion frequencies that have been frequently observed during most earthquakes in Japan. In addition, physical building model based laboratory experiments are also conducted, The results demonstrate the advantages of the proposed nonlinear damping technologies over both traditional linear damping and more advanced Linear-Quadratic Gaussian (LQG) feedback control which have been used in practice to address building isolation system design and implementation problems. In comparison with the tuned-mass damper and other active control methods, the proposed solution offers a more pragmatic, low-cost, robust and effective alternative that can be readily installed into the base-isolation system of most buildings.

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Road Network Evaluation from the Viewpoint of Fire Extinguishing, Fire Spread, and Evacuation to Plan Improvement of District Seismic Safety

Yosuke KAWANISHI and Masayuki KOHIYAMA

Journal of Japan Association for Earthquake Engineering (Japan Association for Earthquake Engineering) 18 ( 2 ) 35 - 50 2018.05

Research paper (scientific journal), Joint Work, Accepted

Road blockage caused by collapsed buildings hinders evacuation, firefighting, and lifesaving activities. It also expands the damage of fire spreading. We propose a method to evaluate the disaster reduction performance of a district with three indices of fire extinguishing probability, ratio of non-burned buildings, and evacuation achievement rate. In the evaluation of these indices, we use the Monte Carlo method based on building collapse rate, fire outbreak probability, etc. As a result of evaluating the proposed indices for two virtual districts: one with latticed road and the other with the radial-ring road, we find that the proposed indices reflect the characteristics of the road network and can express the disaster reduction performance of the districts. In addition, they can facilitate the priority of seismic retrofitting plans considering the characteristics of the district.

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Evaluation of Torsional Vibration Due to Eccentrically-Located Mass and Planer Shape in Wooden Houses under Strong Ground Motion Based on Dynamic Analysis

Kazuya OKA and Masayuki KOHIYAMA

Journal of Structural Engineering (Architectural Institute of Japan) 64B 479 - 492 2018.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 09108033

Time history response analysis was conducted to evaluate torsional response of wooden houses with eccentrically-located mass, such as balconies and solar power panels, under strong ground motion. Five kinds of two-story models were examined and the following findings were observed: (1) In the cases of models with a longer width in the east-west direction, a model with a living room on the first floor showed larger torsional response than that on the second floor because of difference in the amount of walls in the first story. (2) A model with a longer width in the north-south direction showed larger torsional response than that in the east-west direction because of larger eccentric distance. (3) A model with a double-height ceiling room had twice larger response than that without it. Thus, it is necessary to design houses with a double-height ceiling room with careful consideration of torsional response.

Seismic Fragility Function for Ceilings: A Formulation Using Upper Floor Response Acceleration

Kohiyama, M.

Proc. 12th International Conference on Structural Safety and Reliability (International Association for Structural Safety and Reliability) 1873 - 1881 2017.08

Research paper (conference, symposium, etc.), Single Work, Accepted

Contribution of Corporate Social Responsibility to Post-Disaster Life Recovery of Employees

Dan, M. and Kohiyama, M.

Journal of Disaster Research (Fuji Technology Press) 12 ( 4 ) 811 - 821 2017.08

Research paper (scientific journal), Joint Work, Accepted

Corporate social responsibility (CSR) is now considered to be one of the most important activities for companies as it greatly affects both companies and local communities. This study analyzes the effects of corporate social responsibility activities on the life recovery of employees. A questionnaire survey on the Great East Japan Earthquake Disaster in Iwaki City (Fukushima, Japan) was conducted. Iwaki City was among the areas most severely affected by the disaster. The effect of CSR activities on the life recovery of employees was analyzed by structural equation modeling. Life recovery largely depended on health and human relationships. CSR activities related to these two factors, such as work–life balance and local community activities, increased the life recovery of employees. Companies have large resources for improving local community resilience and local communities can recover from a disaster in a timely and effective manner when companies provide appropriate assistance. This study reveals how companies can contribute to the recovery of local communities through their CSR activities.

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Damage Probability Evaluation of a Large Span Steel Frame Based on Dynamic Analysis Considering Load Combination of Earthquake and Snow

Kenji YAMAZAKI and Masayuki KOHIYAMA

Journal of Structural Engineering (Architectural Institute of Japan) 63B 83 - 89 2017.03

Research paper (scientific journal), Joint Work, Accepted

Recently, disasters due to concomitant hazards of earthquake and snow have been increasing in Japan. When engineers verify the structural safety of buildings in a heavy-snow region by means of structural calculation, a coefficient value of 0.35 is used for snow weight under load combination with earthquake with reference to Building Standard Law of Japan. This paper investigates the necessity of load combination of moderate earthquake and moderate snow. The fragility surface of a large span steel frame under seismic excitation and snow load is developed based on dynamic analysis. Two kinds of damage-related responses, the maximum stress of members and the maximum response acceleration of ceilings are examined. With respect to the maximum stress, the evaluated fragility surface and joint hazard surface of earthquake and snow suggest that additional consideration is required for load combination of moderate earthquake and moderate snow.

Seismic Risk Assessment of Wooden Structures near Faults Considering the Locational Uncertainty of Source Area Using the Non-Uniform Slip Model

Seikai, M., Nakahara, S., and Kohiyama, M.

Proc. 16th World Conference on Earthquake Engineering 2017.01

Research paper (international conference proceedings), Joint Work, Accepted

Although the magnitudes of inland earthquakes are smaller than those of earthquakes in subduction zones, they have caused catastrophic disasters in the past. Seismic damage to structures strongly depends on the geometric relationship between a fault and the structure itself, especially near a fault. In recent years, the locations and activities of inland active faults have been identified in Japan. However, the position of a rupture-starting point and rupture extent are uncertain. Together with this uncertainty, we have to consider the difference in the seismic performances of structures, upon which the extent of damage also depends. In this study, seismic ground motions near a fault were simulated with consideration of the above-mentioned uncertainty, and the geometric distribution of the damage probability of wooden structures near a fault was investigated. The effect of seismic performance was also investigated. First, the ground motion with directivity on an engineering bedrock was simulated with a non-uniform slip model of an earthquake-source fault using the stochastic Green’s function. Element seismic waves overtook the phases of neighboring waves. Then, a rupture-starting point was decided stochastically and we assumed that the location of the earthquake-source fault followed a uniform distribution in the possible range. Ground motion on the surface was created by inputting the ground motion into a surface-layer model composed of loam using the one-dimensional equivalent linear analysis. If the maximum shear strain was over 5% in the response analysis result, we trimmed the input waves to maintain their reliability. Wooden structures were modeled considering the restoring force characteristics in accordance with the criteria of three seismic grades. Time-history response analysis was carried out by inputting the ground motion to the building model. Binomial discrimination as to whether or not damage occurred was conducted on the basis of the maximum story drift angle of the building models. Using the results of binomial discrimination, fragility curves assuming a lognormal distribution were constructed for each site using a maximum-likelihood method. Here the peak ground velocity was used as a ground-motion intensity parameter. A stochastic model of earthquake occurrence time was defined in consideration of the uncertainty of the earthquake scale, assuming a stochastic model for the variation of the slip quantity of the earthquake-source fault. We used a Brownian passage time distribution for making these models. Hazard curves of the ground motion were evaluated by this probability model. Finally, the earthquake damage probability of wooden structures was calculated for each site based on the fragility curve and the hazard curve mentioned above. As a result, the influence of the geometric relationship between a fault and the wooden structures and the seismic performance on the earthquake damage probability was obtained. The damage probability of wooden structures was significantly higher in the vicinity of the center of the possible range of the earthquake-source fault. In the vicinity of the fault, earthquake damage probability was reduced more effectively by changing the seismic grade from 1 to 2 than from 0 to 1.

Relation Between CSR Activities and the Resilience of Local Communities in Iwaki City after the 2011 Tohoku Earthquake

Dan, M., Kohiyama, M., and Kiremidjian, A. S.

Proc. 16th World Conference on Earthquake Engineering 2017.01

Research paper (international conference proceedings), Joint Work, Accepted

The concept of resilience is widely used in the disaster management field. In the earthquake-engineering field, many studies have investigated the structural performance of buildings and seismic resilience in terms of performance-based earthquake engineering. However, there are a limited number of studies on the social aspects of resilience. This study focuses on social activities by private companies. A company’s social activity is termed as its Corporate Social Responsibility (CSR). Further, this study also focuses on the relationships between the resilience of a community and the companies’ CSR activities in a local area.
We conducted two questionnaire surveys for citizens and companies in Iwaki City, which suffered from the 2011 Tohoku earthquake. We hypothesized that social activities by companies would improve the resilience of the local community. In the questionnaire surveys, we set two types of respondents as follows: CSR staff of companies and citizens in the local areas. Using the questionnaire responses of the CSR staff, we analyzed characteristics of CSR activities using principal component analysis. Subsequently, using the local citizens’ responses, we compared the differences in their life recovery in terms of economic circumstances and social aspects.

Experimental Study of the Effectiveness of Semi-Actively Implemented Power-Law Damping on Suppressing the Seismic Response of a Base-Isolated Building

Dan, M., Omura, M., Nakamichi, F., Kohiyama, M., and Lang, Z.-Q.

Proc. 6th European Conference on Structural Control (European Association for the Control of Structures) 2016.07

Research paper (international conference proceedings), Joint Work

This study focuses on verifying the effectiveness of the nonlinear power-law damping system on reduction of the vibration of base-isolated buildings with semi-actively implemented dampers over the ranges of resonance frequencies without causing detrimental effects over other frequency ranges. To verify the effectiveness of the proposed power-law damping system, shaking-table tests on a small-scale two-story physical building model are conducted. Random ground motions are used as the input excitations. The physical building model is equipped with a semi-active oil damper whose damping coefficient can be varied over four different values. This provides an effective mechanism for semi-actively implementing the power-law damping system. The shaking-table tests have demonstrated the effectiveness and robustness of the power-law damping and indicated that this can be a more practical solution to improving the performance of building base-isolation systems.

Shaking Table Tests of Cooperative Control between an Active Mass Damper for a Building and Semi-Active Damper for a Base-Isolated Floor Using a Small-Scale Specimen

Nakamichi, F. and Kohiyama, M.

Proc. 6th European Conference on Structural Control (European Association for the Control of Structures) 2016.07

Research paper (international conference proceedings), Joint Work

To reduce the amount of earthquake damage, the effectiveness of cooperative control between two controllers (one for the building and another for the equipment) was verified using a shaking table test. We employed a Kalman filter and the linear quadratic Gaussian strategy to minimise the amount of damage under strong ground motions, and the two controllers share the quantities of the state variables of the building and equipment. A three-storey specimen, which comprise a building (the main system) with an active mass damper and a base-isolated floor (a subsystem) with a semi-active oil damper, represents a 15-storey building of a data centre on a real scale. As a result of the shaking table test, we confirmed that implementing cooperative control reduced the relative displacement between the main system and subsystem without increasing absolute acceleration.

Experimental Study on Application of Electro-Adhesive Gel Damper to Based-Isolated Building Using Small-Scale Specimen

Omura, M., Kohiyama, M., Kakinuma, Y., and Anzai, H.

Proc. 6th European Conference on Structural Control (European Association for the Control of Structures) 2016.07

Research paper (international conference proceedings), Joint Work

Control methods for a semi-active damper using Electro-Adhesive Gel (EAG) are analysed. Modelling of an EAG damper is conducted based on approximation of the force-voltage relation obtained from experimental data. The performance of an EAG damper is evaluated by shaking-table tests of a two-story small-scale specimen. The specimen is designed to adjust the ratio between first and second natural periods to that of a target real-scale base-isolated building, and system parameters are identified based on vibration response under white noise excitation. An EAG damper is implemented to the base-isolation layer of the small-scale specimen. Acceleration sensors are attached to each layer to acquire response data. As an observer in a control system, a Kalman filter is employed, and for a controller, LQG strategy and disturbance accommodating control are advocated to apply the suitable input voltage to the EAG damper. The cost function of the LQG is formulated to suppress the acceleration response of the specimen. Experiments using other control methods, simulated nonlinear spring and simulated dashpot, are also conducted for comparison. With respect to the input excitation, scaled earthquake ground motion records are used. Based on the results of the shaking-table tests, we report the validity of the EAG damper and discuss about effective control methods.

Design of Control Parameter of Sliding Mode Control Reducing Damage Probability of Semi-Actively Controlled Base-Isolated Building

Shizuka WAKAYAMA and Masayuki KOHIYAMA

Journal of Japan Association for Earthquake Engineering (Japan Association for Earthquake Engineering) 16 ( 3 ) 75 - 93 2016.03

Research paper (scientific journal), Joint Work, Accepted

A sliding mode control is one of control methods with superior robustness against structural parameter change and uncertainty of a model. However, a sliding mode control requires multiple control parameters and a design method of these parameters has not been established. In this study, we propose a design procedure to determine the control parameters so as to minimize the damage probability in a certain service period of a building. A semi-actively controlled base-isolated building is studied and the damage probability based on the proposed design procedure is compared with that based on a conventional procedure that determines parameters to minimize the response under design input ground motion with a certain level of intensity.

Finite-Element Analysis of Laminated Rubber Bearing of Building Frame under Seismic Excitation

Ohsaki, M., Miyamura, T., Kohiyama, M.,Yamashita, T., Yamamoto, M., and Nakamura, N.

Earthquake Engineering and Structural Dynamics (John Wiley & Sons) 44 ( 11 ) 1881 - 1898 2015.09

Research paper (scientific journal), Joint Work, Accepted

Finite element analysis is carried out for simultaneously investigating global displacement and local stress responses of laminated rubber bearings under earthquake excitation. Natural rubber bearings are attached at the base of a building frame. The frame members as well as the rubber bearings are discretized into hexahedral finite elements with more than 3 million degrees of freedom. The material properties of rubber are represented by the Ogden model, and the frame is assumed to remain in elastic range. It is shown that the incompressible and hardening properties of natural rubber can be accurately simulated, and the deformation and stress distribution of rubber bearings of a frame under seismic excitation are successfully evaluated through a finite element analysis.

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Shaking Table Experiment of Fault-Tolerant Seismic Vibration Control of a Building Based on Sensor Reliability

Tanaka, S. and Kohiyama, M.

Proc. 12th International Conference on Applications of Statistics and Probability in Civil Engineering 1 - 7 2015.07

Research paper (international conference proceedings), Joint Work, Accepted

The authors propose a compensation method using the Kalman filter and sensor reliability parameters to assure the continuous performance of vibration control even if sensor failures occur. The effectiveness of the proposed method was verified by conducting a shaking table test using a three-story specimen with an active mass damper, which is a small-scale model of a 15-story building. As a result of the shaking table test with simulated sensor damage, it was confirmed that the responses of inter-story drift angle and absolute acceleration were reduced by the proposed compensation method in comparison with a case without the proposed method.

Maximum Response Estimation of a Mid-Story Isolated Building Based on Complex Complete Quadratic Combination Method Considering Mode-Dependent Peak Factors

Ishizawa, Y. and Kohiyama, M.

Theoretical and Applied Mechanics Japan (National Committee for IUTAM, Science Council of Japan) 63 67-79 2015.07

Research paper (scientific journal), Joint Work, Accepted

We conducted a theoretical analysis of the peak factor, defined as the ratio of the response maximum to the response standard deviation of a single-degree-of-freedom system. We constructed a peak factor formula that uses the natural circular frequency, damping factor, and duration of ground motion, and thereby estimated the peak factor of each mode of a multi-degree-of-freedom system. Using these mode-dependent peak factors, we then modified the existing complex complete quadratic combination method to estimate the maximum acceleration of a non-classically damped model. The response of a mid-story isolated building model under white noise ground motion was analyzed, and it was confirmed that the reformed formula globally provides good estimates in most cases.

Optimization of member sections of a tensegrity structure considering large displacements during an earthquake

Miura, Y. and Kohiyama, M.

Proc. IASS WORKING GROUPS 12 + 18 International Colloquium 2015 "Bio-based and Bio-inspired Environmentally Compatible Structures" (International Association for Shell and Spatial Structure) 1 - 8 2015.04

Research paper (international conference proceedings), Joint Work

In this study, we propose a method to optimize sections of a tensegrity structure considering large displacements during

a large earthquake. Although there are multiple studies about the self-equilibrium of tensegrity structures, a method for

their optimization or dynamic analysis that considers large displacements has not yet been proposed. Because a

tensegrity system is a combination of struts and cables, i.e., compressive and tensile members, non-linear analysis is

required to obtain realistic appropriations of displacements resulting from strong ground motions. We study the

optimization of the minimum unit of a tensegrity structure and investigate the mode shape of the optimal design.

Vibration characteristics change of a base-isolated building with semi-active dampers before, during, and after the 2011 Great East Japan earthquake

Dan, M., Ishizawa, Y., Tanaka, S., Nakahara, S., Wakayama, S., and Kohiyama, M.

Earthquakes and Structures (Techno Press) 8 ( 4 ) 889 - 913 2015.04

Research paper (scientific journal), Joint Work, Accepted, ISSN 2092-7622

Structural vibration characteristics of a semi-active base-isolated building were investigated using seismic observation records including those of the 2011 Great East Japan earthquake (Tohoku earthquake). Three different types of analyses were conducted. First, we investigated the long-term changes in the natural frequencies and damping factors by using an ARX model and confirmed that the natural frequency of the superstructure decreased slightly after the main shock of the Tohoku earthquake. Second, we investigated short-term changes in the natural frequencies and damping factors during the main shock by using the N4SID method and observed different transition characteristics between the first and second modes. In the second mode, in which the superstructure response is most significant, the natural frequency changed depending on the response amplitude. In addition, at the beginning of the ground motion, the identified first natural frequency was high possibly as a result of sliding friction. Third, we compared the natural frequencies and damping factors between the conditions of a properly functional semi-active control system and a nonfunctional system, by using the records of the aftershocks of the Tohoku earthquake. However, we could not detect major differences because the response was probably influenced by sliding friction, which had a more significant effect on damping characteristics than did the semi-active dampers.

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Detailed Finite Element Analysis of Full-scale Four-story Steel Frame Structure subjected to Consecutive Ground Motions

Tagawa, H., Miyamura, T., Yamashita, T., Kohiyama, M., and Ohsaki, M.

International Journal of High-Rise Buildings (Council on Tall Buildings and Urban Habitat) 4 ( 1 ) 65 - 73 2015.03

Research paper (scientific journal), Joint Work, Accepted

Detailed finite element (FE) analyses of a full-scale four-story steel frame structure, subjected to consecutive 60% and 100% excitations from the JR Takatori records during the 1995 Hyogoken-Nanbu earthquake, are conducted using E-Simulator. The four-story frame was tested at the largest shake-table facility in the world, E-Defense, in 2007. E-Simulator is a parallel FE analysis software package developed to accurately simulate structural behavior up to collapse by using a fine mesh of solid elements. To reduce computational time in consecutive dynamic time history analyses, static analysis with gravity force is introduced to terminate the vibration of the structure during the analysis of 60% excitation. An overall sway mechanism when subjected to 60% excitation and a story mechanism resulting from local buckling of the first-story columns when subjected to 100% excitation are simulated by using E-Simulator. The story drift response to the consecutive 60% and 100% excitations is slightly smaller than that for the single 100% excitation.

Fault-Tolerant Seismic Vibration Control of a Building with Sensor Reliability Evaluated by the Kalman Filter

Tanaka, S. and Kohiyama, M.

Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management (CRC Press) 1140 - 1146 2014.11

Research paper (international conference proceedings), Joint Work, Accepted

Strong earthquake ground motions hinder the use of seismic vibration control systems in buildings because they may damage the sensors or cables connected to controllers. To maximize the vibration control of the building even during large earthquakes, we designed a redundant vibration control system that tolerates errors in sensing instruments and the accuracy deterioration in the estimated state variables. To monitor the accuracy of each sensor, we introduced a reliability parameter that quantifies the accuracy of the estimated state variables. Using this, we designed a new algorithm based on linear-quadratic Gaussian control theory to reduce the building seismic response and obtain a redundant and robust building vibration control system.

Evaluation of Seismic Retrofitting Priority of Houses Based on Evacuee Isolation Probability Using Markov Chain Monte Carlo Method

Masayoshi TODAKA and Masayuki KOHIYAMA

Journal of Japan Association for Earthquake Engineering (Japan Association for Earthquake Engineering) 14 ( 5 ) 19 - 30 2014.11

Research paper (scientific journal), Joint Work, Accepted

We propose a new method to evaluate the effectiveness of seismic retrofitting of houses for evacuation quantitatively. The priority of houses that should be retrofitted is evaluated based on a probability to yield isolated evacuees due to road blockade caused by debris of collapsed houses after a severe earthquake. We improve the method to extract samples using the Markov chain Monte Carlo method. An index is newly introduced to evaluate the retrofitting priority, which is difference of expected numbers of isolated evacuees in a target area between before and after the retrofitting. The proposed method can show retrofitting priority of houses effectively when the ground motion intensity is assumed to be JMA Seismic Intensity 6 upper.

Detailed finite element analysis of composite beam under cyclic loads

Yamashita, T., Ohsaki, M., Kohiyama, M., Miyamura, T., Zhang, J., and Tagawa, H.

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 79 ( 704 ) 1481 - 1490 2014.10

Research paper (scientific journal), Joint Work, Accepted

Modeling and numerical simulation techniques for performing a detailed finite element analysis of a composite beam are presented. The finite element analysis is performed using E-Simulator, which is under development at the Hyogo Earthquake Engineering Research Center (E-Defense) of the National Research Institute for Earth Science and Disaster Prevention (NIED). A piecewise linear isotropic-kinematic hardening law is used for the steel material, and heuristic and implicit rules are incorporated to simulate its complex cyclic elastoplastic behavior. The extended Drucker-Prager model is used for the concrete material. The steel beam, steel column and reinforced concrete slab are discretized into solid elements. The wire mesh consisting of steel bars in the slab is also modeled using solid elements and rigid beams are used for the stud bolts. Detailed analyses are carried out for both a steel beam and a composite beam subjected to static cyclic loading. Good agreement is found with experimental results such as strength degradation due to local buckling of the flange, and asymmetric behaviors resulting from contact between the slab and the column.

Optimal management of public real estate under seismic risk using real option approach

Dan, M. and Kohiyama, M.

Proc. 3rd International Conference on Urban Disaster Reduction (Earthquake Engineering Research Institute) 1 - 4 2014.09

Research paper (international conference proceedings), Joint Work

This study focuses on the scheduling in public real estate management (PREM) and derives the optimal scheduling using real option approach considering seismic risk. This study defines a seismic risk as the uncertainty in PREM and proposes a method to derive the optimal scheduling of seismic retrofitting of facilities managed by a municipality using real option considering seismic risk. To verify the effectiveness of the proposed method, this study conducts a case study. A retrofitting problem of school facilities in Kawasaki City, Japan is selected as a case study subject. Through the case study, it is confirmed that the proposed method can derive the optimal retrofit schedule with a reduced cost and a reduced risk of damage due to earthquakes.

Finite element analysis of damping mechanism of autoclaved lightweight aerated concrete panels for exterior walls of steel structures

Kohiyama, M., Ohsaki, M., Miyamura, T., and Yamashita, T.

Proc. 11th World Congress on Computational Mechanics 2229 - 2236 2014.07

Research paper (international conference proceedings), Joint Work

To improve the damping models of building structures, the mechanical behavior of exterior walls made of autoclaved lightweight aerated concrete (ALC) is investigated using finite element analysis software, E-Simulator. A specimen of ALC panels and a loading apparatus are modeled using solid elements, rigid beams and multi-point constraints, which reproduce a rocking installation system used in tests of components of a real-scale four-story steel structure for shaking table tests of E-Defense, National Research Institute of Earth Science and Disaster Prevention. Static alternately repeated cyclic loading with incremental deformation amplitude is simulated up to the drift angle of 0.02 rad. It is observed that energy dissipation owing to the plastic deformation of the ALC panels and the friction between an ALC panel and a ruler steel angle becomes remarkably large when the drift angle exceeds 0.015 rad because of the contact.

Vibration Controller Design of a Building–Equipment System Based on the Seismic Damage Risk

Kohiyama, M. and Ito, T.

Proc. 6th World Conference on Structural Control and Monitoring 2014.07

Research paper (international conference proceedings), Joint Work

A design framework is investigated for designing the parameters of a vibration control device installed in a building–equipment coupled system to reduce earthquake damage. An iterative calculation procedure to derive a suboptimal design based on the minimization of damage probability in a certain service period is proposed. The validity of the proposed procedure is examined using a model of a fifteen-storied data-center building that accommodates servers on isolated floors on the second and fifteenth floors and is equipped with a vibration control device on the top floor. The proposed procedure is confirmed to give a suboptimal design within a few calculation iterations.

Simultaneous Optimization of Structural Shape and Control System of Large-Scale Space Frame Based on Sine Wave Inputs

Dan, M. and Kohiyama, M.

International Journal of Safety and Security Engineering 4 ( 2 ) 164-178 2014.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 2041-9031

A simultaneous optimal design method of asymmetric large-scale space frames with tuned mass dampers is proposed. The objective function is defined by the maximum absolute acceleration response of the structure to input ground motions of sine waves. Sine waves of periods with the five natural periods having large modal participation factors of the structure are input, and the maximum responses are calculated by time–history response analysis to evaluate the objective function. The shape of the space frame is described by a Bézier surface to reduce the number of design variables. The change from the initial values of the nodal coordinates is constrained to preserve the initial design shape, which is provided by an architect. The method employs a genetic algorithm in optimization. A case study is conducted for an asymmetric steel space frame of a vault-like shape. The results confirm the reduction of maximum absolute acceleration responses in the optimal shapes not only to the five sine waves but also to four scaled ground motion records. Moreover, the presence of tuned mass dampers enables the reduction of the peak response value and maintains similarity to the initial shape.

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A Robust Decentralized Control Method Based on Dimensionless Parameters with Practical Performance Criterion for Building Structures under Seismic Excitations

Giron, N. and Kohiyama, M.

Structural Control and Health Monitoring (John Wiley & Sons, Inc.) 21 ( 6 ) 907 - 925 2014.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 1545-2263

A robust and decentralized control method for reducing vibration in a building, based on the Lyapunov-control function, is proposed and investigated. A new parameter that gives flexibility to the control design is introduced, and the control law is expressed in terms of dimensionless parameters. In addition, an expression adapted for semiactive control of which feedback gain is finite is proposed for a particular case. Analytical proof of the performance is completely derived for a system in which the control distribution matrix is not singular and a practical performance criterion is obtained. The influence of each parameter, along with the validity of the proposed performance criterion and the robustness to the uncertainties in the structural parameters, is extensively discussed with a single-degree-of-freedom numerical example. The performance of a decentralized system and the controller design in the case where the control distribution matrix is singular are discussed with a two-degree-of-freedom numerical application. A shaking table experiment using a small-scale model of a high-rise building with a vibration control device is conducted to verify the proposed method.

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LQG design scheme for multiple vibration controllers in a data center facility

Kohiyama, M. and Yoshida, M.

Earthquakes and Structures (Techno Press) 6 ( 3 ) 281 - 300 2014.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 2092-7622

This study proposes a scheme to design control parameters for a data center facility with a vibration controller on its top floor and a secondary isolation device with its own vibration controller designed to protect vibration-sensitive computer equipment. The aim is to reduce the effects of acceleration and drift from an earthquake on computer servers placed on the isolation device that must operate during a seismic event. A linear elastic model is constructed and the evaluation function of the linear quadratic Gaussian (LQG) control is formulated. The relationship between the control parameters and the responses is examined, and based on the observations, a control parameter design scheme is constructed to reduce the responses of both the building and the computer server effectively.

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ロボットを用いた効果的な屋内避難誘導のための被験者実験に基づくエージェントモデル

Masayuki KOHIYAMA and Minami KANEKO

Journal of Social Safety Science (Institute of Social Safety Science) ( 22 ) 1 - 10 2014.03

Research paper (scientific journal), Joint Work, Accepted

Evacuation assistance using a robot is studied. Human subjects experiments of indoor evacuation under robot guidance were conducted and the result showed effectiveness of a robot guidance in the evacuation. Based on the experiment result an agent model for evacuation simulation was conducted. The agent model considers probability distributions of the walking speed and the route decision time of evacuees. Using the constructed agent model, evacuation simulation was carried out for a building with complex hallways. It is demonstrated that effective position of a robot for guidance can be sought through the agent simulation.

Finite Element Analysis of Contact at Corner of ALC Panel Using E-Simulator

Masayuki KOHIYAMA, Makoto OHSAKI, Tomoshi MIYAMURA, and Takuzo YAMASHITA

Journal of Structural Engineering (Architectural Institute of Japan) 60B 463 - 470 2014.03

Research paper (scientific journal), Joint Work, Accepted

The mechanical behavior of exterior walls made of autoclaved lightweight aerated concrete (ALC) is investigated using finite element analysis. A specimen of ALC panels and a loading apparatus, which reproduce a rocking installation system, are modeled using solid elements, rigid beam elements and multi-point constraints. The finite element analysis software, E-simulator, is employed to simulate static alternately repeated cyclic loading with incremental deformation amplitude up to the drift angle of 1/50 rad. It is clarified that plastic deformation of the concrete panels, which causes the energy dissipation, is observed in the region around the O bolts and the corners that come into contact with a supporting bottom angle.

System identification and control improvement of a semi-active-controlled base-isolated building using the records of the 2011 Great East Japan Earthquake

Dan, M. and Kohiyama, M.

Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures (Taylor & Francis Group, London) 3841-3847 2013.12

Research paper (international conference proceedings), Joint Work, Accepted

Sosokan, a building at the Yagami Campus of Keio University, has a semi-active control system that include 8 semi-active dampers and 24 passive dampers installed in the base-isolation layer. The parameters of the semi-active controller were designed using the initially assumed design values of the building. However, these parameters may not be identical to its present actual condition and can be updated on basis of observation records. This paper aims to improve the performance of the controller through identification of the building properties by updating the control parameters on basis of the records of seismic responses during the main shock and aftershocks of the 2011 Great East Japan Earthquake. In the identification, errors between the time history responses of the main shock records and simulation results are minimized by an optimization scheme. Thereafter, structural properties of the updated building model is applied to improve the performance of the semi-active controller.

Prediction of maximum control force of PD-controlled system under stationary white noise

Kohiyama, M.

Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures (Taylor & Francis Group, London) 3871-3878 2013.12

Research paper (international conference proceedings), Single Work, Accepted

A method for predicting the maximum control force of a proportional-derivative controlled system is pro-posed based on a response spectrum method. In designing structural control devices for the reduction of seis-mic response, it is important to choose an actuator with an adequate control force capacity in order to achieve a satisfactory control effect. To accomplish this, the maximum control force under assumed seismic ground motions has to be estimated. To verify the proposed method, the predicted maximum forces are compared with the results of a time-history analysis using white noise and design ground motions. With respect to the analysis models, three-story and 25-story building models with active bracing for each story are used. It is found that the differences between the predicted values of the maximum response and control force and the time-history analysis results are sufficiently small, and thus the proposed method is reliable to use in design.

Seismic vibration control of a building considering fragility curves of accommodated computer servers

Ito, T. and Kohiyama, M.

Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures (Taylor & Francis Group, London) 3857-3862 2013.12

Research paper (international conference proceedings), Joint Work, Accepted

The inability of equipment and instruments in a building to function is one of the serious effects of seismic ground motion. We discuss the situation of computer servers in a data center and the required linear optimum control of a building to reduce the damage. We construct a mass–shear spring model of a building that con-tains computer servers on a seismic isolation floor and that is equipped with an active vibration controller on the top floor. Simulated ground motions are input to the model, and the maximum responses are examined to evaluate the fragility curve of the server. Finally, we propose a technique that can be used to design parame-ters of a controller, enabling a reduction in damage to the servers.

Evaluation of Seismic Retrofitting Effectiveness for District Evacuation Safety Based on Evacuees' Isolation Probability by Using Markov Chain Monte Carlo Method

Todaka, M. and Kohiyama, M.

Proc. 2nd JAEE International Symposium (Japan Association for Earthquake Engineering) 2013.11

Research paper (international conference proceedings), Joint Work

We propose a new quantitative method to evaluate the effectiveness of seismic retrofitting of houses for evacuation safety. The priority of houses that need retrofitting is evaluated on the basis of the probability of evacuees becoming isolated owing to road blockades caused by the debris of collapsed houses after an earthquake. We improve the method to extract samples by using the Markov chain Monte Carlo method. A new index is introduced to evaluate the difference of total expected numbers of isolated evacuees before and after the retrofitting.

Seismic Vibration Control of a Multi-Story Building Considering Damage Risk of Accommodated Computer Servers

Ito, T. and Kohiyama, M.

MJIIT-JUC Joint International Symposium 2013.11

Research paper (international conference proceedings), Joint Work, Accepted

The loss of a building function is one of the serious effects of seismic ground motion. We discuss the situation of computer servers in a data center and the required linear optimum control of a building to reduce the damage. We construct a model of a building that contains computer servers on a seismic isolation floor and that is equipped with an active vibration controller on the top floor. Simulated ground motions are input to the model, and the maximum responses are examined to evaluate the fragility curve of the server. Finally, we investigate design parameters of a controller which enable a reduction in damage risk of the servers placed on different floors.

LQG Design Scheme for Multiple Vibration Controllers in a Building–Equipment System Considering the Maximum Control Force

Kohiyama, M. and Yoshida, M.

the 2013 World Congress on Advances in Structural Engineering and Mechanics 1229-1236 2013.09

Research paper (international conference proceedings), Joint Work

A method to determine a control scheme and parameters is proposed for a data center facility with a vibration controller on its top floor and a secondary isolation device with its own vibration controller designed to protect delicate computer equipment. The aim is to reduce acceleration and drift from an earthquake for computer servers placed on the isolation device that must operate during a seismic event. A linear elastic model was constructed and the evaluation function of the linear quadratic Gaussian control was formulated. The relationship between control parameters and responses was examined, and it was confirmed that the proposed scheme properly defined system parameters to minimize the responses of both the building and computer server.

多分野をつなぐ性能設計

Masayuki KOHIYAMA

2013年度日本建築学会大会（北海道）構造部門（荷重）パネルディスカッション資料「建築物の性能設計・再考―想定外事象も踏まえて」 (日本建築学会) 15-20 2013.08

Research paper (conference, symposium, etc.), Single Work

設備や非構造部材の被害を低減するためには設計者・技術者間のコミュニケーションが不可欠である。人命保護などの要求性能にはサブ性能のヒエラルキーが存在しており、役割分担と協調のため、性能というコンセプトで展開される技術コミュニケーションが作り手側に求められる。また、構造設計者は、利害関係者の要望を吸い上げ、安全性能を具体化し実現するプロセスにより積極的に関わるべきである。従来の耐震設計などの性能チェックにとどまらず、多分野と連携し、居住性や事業継続性など建築主や社会のニーズに応えた建物を実現する性能設計の普及を期待する。

Optimal stiffness distribution of mid-storey-isolated buildings considering storey drift and floor acceleration response

Kohiyama, M. and Takano, K.

Earthquake Resistant Engineering Structures IX, Brebbia, C.A. and Hernández, S. eds. (9th World Conference on Earthquake Resistant Engineering Structures) (WIT Press, Southampton, UK / University of A Coruña, Spain and Wessex Institute of Technology, UK) 10 191-202 2013.07

Research paper (international conference proceedings), Joint Work

This paper formulates a response prediction formula based on complex modal superposition and frequency response functions of single-degree-of-freedom systems for both storey drift and floor acceleration of a mid-storey-isolated building under the assumption of white noise input. This study verifies that the proposed formula can estimate the seismic response of a building accurately, even if a system includes the overdamped mode, by comparing the same with the results of a time-history analysis. To support the structural design of a mid-storey-isolated building, the proposed formula is applied to an optimal design problem, which considers the objective function of acceleration response in a superstructure and constraints on storey drifts. A genetic algorithm is employed to obtain the optimal stiffness distribution and damping coefficient of the isolation layer. This study confirms that the acceleration response of the optimal design is successfully reduced, with other responses remaining within acceptable ranges.

Simultaneous optimization of structural shape and control system of large-scale space frame

Dan, M. and Kohiyama, M.

Research paper (international conference proceedings), Joint Work

In general, large-scale space frames, such as stadiums and gymnasiums, have a role as an evacuation facility. However, some accidental falls of a ceiling and equipment during an earthquake have been reported, and these accidents might cause human injury or casualty. On the other hand, these structures often have an aesthetically elaborated design, but they do not always have high performances from a structural point of view. This research proposes a method to support designing a large-scale space frame, which implements: 1) a design elaborated by an architect and 2) structural and control performances, which can reduce damage or fall of a ceiling, on the basis of simultaneous optimization of structural and control systems. The number of design parameters in the optimization problem is reduced by describing the roof shape with a Bézier surface. The genetic algorithm is used for the optimization.

Dynamic collapse analysis of four-story steel frame using E-Simulator

Miyamura, T., Ohsaki, M., Yamashita, T., Isobe, D., and Kohiyama, M.

4th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2013) (European Community on Computational Methods in Applied Sciences and International Association for Computational Mechanics) 12 2013.06

Research paper (international conference proceedings), Joint Work

Dynamic collapse analyses of a 4-story steel building frame modeled by solid elements are performed using the E-Simulator, which is a parallel finite element analysis software package for civil and building structures. Code verification, calculation verification, and validation of the numerical codes (V&V) are conducted by comparing the results obtained by the E-Simulator, those obtained by a beam element analysis code, and the experimental results obtained by the 3-D full-scale earthquake testing facility, the E-Defense at NIED. The seismic response analyses under 60% or 100% of the JR Takatori seismic wave of the 1995 Hyogoken-Nanbu earthquake are performed. The shear forces and interstory drift angles of the 1st story obtained by the E-Simulator simulation and the E-Defense full-scale test have good agreement. Both response of the whole frame and local deformation due to plastic buckling are simulated in the analysis using the E-Simulator.

High-precision finite-element analysis of rubber bearing for base-isolation of building structures

Ohsaki, M., Miyamura, T., Kohiyama, M., Yamashita, T., Yamamoto, M., and, Nakamura, N.

Research paper (international conference proceedings), Joint Work

Seismic response analysis is carried out for a base-isolated frame. The RC-frame members as well as the rubber bearings are discretized into hexahedral finite elements. The material properties of rubber are represented by the Ogden model, and the frame is assumed to remain in elastic range. The seismic response analysis of the frame, which has more than 3 million degrees of freedom is carried out using the E-Simulator, which is under development at E-Defense, Japan, based on a software package called ADVENTURECluster. It is shown that the global and local responses can be simultaneously evaluated through a high-precision finite element analysis.

Design Method of a Quadratic Cost Function for Vibration Control to Maintain Functions of a Building During an Earthquake

Nanako Miura and Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 78 ( 687 ) 923-929 2013.05

Research paper (scientific journal), Joint Work, Accepted

It is important to maintain functions of a building such as providing medical services, performing production operations, and dwelling during and after an earthquake. Until now, vibration control devices have been devised and installed in many buildings. To maximize the control effects under the limited capacity of a control force, a method for constructing an evaluation function on the basis of the prescribed control objectives is proposed, in which the control objectives are expressed as dimensionless numbers using the required performance levels. The effectiveness of the proposed method is verified by a time-history analysis.

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Numerical Model of Mechanical Coupling for Interior Open Piping Considering Nonlinear Behavior

Kaoru KINOSHITA, Masayuki KOHIYAMA, Masayuki OHSAWA, and Shinobu KAWAGUCHI

Journal of Structural Engineering (Architectural Institute of Japan) 59B 119-126 2013.03

Research paper (scientific journal), Joint Work, Accepted

屋内ガス配管用機械式継手の数値解析モデルを曲げ実験・震動台実験の結果に基づき2種類構築した。まず，硬化型特性を持つバイリニアばね・線形弾性ばね複合モデルを構築した。次に，Ozdemirモデル・線形ばね・ギャップクロージングばねに基づき非線形のヒステリシス特性を持つばねを構築した。震動台実験を再現する時刻歴応答解析を行い，モデルの妥当性の評価を行ったところ，後者のモデルは応答レベルが小さい場合に良好に実験を再現することを確認した。

Shaking Table Test of Seismic Response Control of Building-Elevator System Using Vibration Control Device on the Top Floor

Keisuke WATANABE, Nanako MIURA, Masayuki KOHIYAMA, and Masaki TAKAHASHI

Journal of Structural Engineering (Architectural Institute of Japan) 59B 339-348 2013.03

Research paper (scientific journal), Joint Work, Accepted

近年報告されているエレベータロープの地震被害を低減するため、アクティブマスダンパー(AMD)や連結制振などの建物用の制振装置を用いた制御手法を提案した。提案手法は建物とロープの両方の安全確保を目標とした線形二次ガウシアン制御に基づいている。提案手法の有効性を実証するため、超高層建物の縮小モデルであるアルミ製の4層試験体を用いた実験を行った。エレベータロープは銅の薄板でモデル化し、AMDを試験体の最上層に設置した。震動台実験を行った結果、提案手法はエレベータロープの応答を低減することを確認した。

Simultaneous Optimization of Structural and Control Systems of a Multi-Story Building With PD Controlled Active Braces Using Design Response Spectra

Masayuki KOHIYAMA and Chihiro HORIGUCHI

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 78 ( 683 ) 71-80 2013.01

Research paper (scientific journal), Joint Work, Accepted

An optimization method is developed for the structural and control systems of a multi-story building equipped with proportional-derivative (PD) controlled active braces. The method uses design response spectra to consider ground motions and employs the complex complete quadratic combination method to estimate the maximum response and the maximum control force. Both structural and control costs are minimized under the constraints of the maximum inter-story drift and the absolute acceleration responses. The proposed method is applied to the simultaneous optimization of a three-story building with PD-controlled active braces and it is demonstrated that the method can efficiently provide Pareto optimal solutions.

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Evaluation Method of Seismic Safety of Interior Piping Using Single-Axis Shake-Table Test and Finite Element Analysis

Ohsawa, M., Kawaguchi, S., Atarashiya, Y., Nakakomi, A., Kinoshita, K., and Kohiyama, M.

15th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 2012.09

Research paper (international conference proceedings), Joint Work

As a first step to establishing a reliable numerical simulation model for interior city-gas piping, some cases of shake-table tests for a partial-piping specimen were conducted. Static bending tests using almost the same supporting apparatus as the shake-table test were also conducted to obtain the mechanical characteristics of the clamp, the hanging bolt and the mechanical coupling, and simplified analytical models were investigated for the non-coupling specimen and for the with-coupling specimen. Finite element analyses (FEA) were then carried out for these models. The experimental data regarding the seismic response during the shake-table tests generally agreed with the FEA results. It was therefore inferred that the major structure of the analytical models proposed in this study is adequate to evaluate seismic safety for interior city-gas piping.

Health Disturbance of Residents in Houses Tilted Due to Liquefaction during the Great East Japan Earthquake

Kohiyama, M. and Keino, C.

15th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 2012.09

Research paper (international conference proceedings), Joint Work

The 2011 off the Pacific coast of Tohoku Earthquake triggered liquefaction of soil in wide areas of Japan. In particular, a number of damaged houses were found in the land reclamation areas of the Kanto region. Some residents who lived in houses that were tilted by liquefaction complained of health disorders. We report on the results of a questionnaire survey of residents in Mihama Ward, Chiba City, about the characteristics of their houses, earthquake damage, health disturbances, and so on. Probability models of health disturbance with respect to house tilt angle due to liquefaction are constructed based on the survey data. The probability that a respondent experienced health disturbance was found to be considerably higher when the tilt angle exceeded 0.013 rad.

Comparative Study Between Centralized and Decentralized LQR Controls of a Building-Elevator System

Yoshida, M., Kohiyama, M., and Takahashi, M.

15th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 2012.09

Research paper (international conference proceedings), Joint Work

When both a building and its equipment have a vibration controller, the controller of the equipment should consider the behaviour of the building and vice versa. First, we classified control schemes according to the amount of state variables communicated between the controllers and the type of control objectives. Then, a high-rise building with an elevator system is analysed under seismic excitation to compare the performance of the classified control schemes that use a linear quadratic regulator. It is observed that the story drift and the response of the elevator rope are best reduced when all the state variables are communicated, but they can be sufficiently reduced even if not all the state variables are communicated.

Vibration Reduction of a Building-Elevator System Considering the Intensity of Earthquake Excitation

Miura, N. and Kohiyama, M.

15th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 2012.09

Research paper (international conference proceedings), Joint Work

To maximize the control effects under the limited capacity of a control force, a control method based on variable gain feedback control for a coupled model of a building and an elevator is proposed. In this method, a controller selects a proper control objective and prevents the saturation of the control force considering the intensity of the ground motion and the associated building response level. For preventing saturation, the maximum required control force is estimated on the basis of the square root of sum of squares (SRSS) method using the input ground acceleration. The effectiveness of the proposed method is verified by a time-history analysis. The analysis is performed using the long-period ground motion record of the 2011 off the Pacific coast of Tohoku Earthquake, 100 simulated waves with the peak ground velocity of about 25 cm/s2 and 300 waves obtained by scaling the simulated waves.

実践的な性能設計／地震リスクマネジメント，2011年度日本建築学会大会（北陸）構造部門（荷重）パネルディスカッション

KOHIYAMA MASAYUKI

建築雑誌 (日本建築学会) 127 ( 1635 ) 22-24 2012.09

Research paper (scientific journal), Single Work

High-precision FE-analysis for global and local elastoplastic responses of building frames

Ohsaki, M., Kohiyama, M., Miyamura, T., Yamashita, T., and Akiba, H.

International Symposium on Reliability Engineering and Risk Management 2012 (Kanagawa University, Tongji University, Central South University and the International Association of Structural Safety and Reliability) 561 - 566 2012.08

Research paper (international conference proceedings), Joint Work

Global and local responses of steel frames are simultaneously simulated using a high-precision finite element (FE) analysis considering composite beam effects. A detailed analysis is first carried out for a 4-story building frame subjected to seismic motion. The steel material is modeled using a piecewise linear isotropic-kinematic hardening that can incorporate a yield plateau. Static cyclic response analysis is then carried out for a compo-site beam supported by a column. It is demonstrated that the experimental results, which show asymmetric behaviors due to contact of the slab to the column, can be simulated accurately using the high-precision FE-analysis.

Influence of the number of samples of simulated earthquake motions on accuracy of seismic risk assessment of a two-story house

Watanabe, T. and Kohiyama, M.

Research paper (international conference proceedings), Joint Work

入力地震動数と建物地震被害リスクの精度の間の関係について，動的解析に基づく手法とハザード曲線・フラジリティ曲線に基づく手法の2つに関し分析を行った。まず，マグニチュード・震源距離・震源深さの組合せの各ケースについて，1000波の模擬地震動を作成した。次に，モンテカルロシミュレーションを行い，2階建て木造建物の地震被害を評価した。限定数の解析結果を用い，上記の2通りの手法で30年間の被害発生確率を計算した。その結果，2手法とも同数の入力波で同程度の精度となることを確認した。

Simultaneous optimization of structure and control under seismic excitation uncertainties with unified cost function

Giron, N. and Kohiyama, M.

Research paper (international conference proceedings), Joint Work

地震動を受ける鉄筋コンクリート造建物の制御と構造の同時最適化手法の提案を行った。設計変数は各層の剛性，制御装置の位置，スライディングモード制御パラメータで，目的関数であるライフサイクルコストは，初期費用，修復費用からなる。最適化には遺伝的アルゴリズムとネルダー・ミード法を用いた。入力地震動は模擬地震動を用い，非線形時刻歴応答解析により修復費用を推定した。4層建物モデルを用い，提案手法の有効性を確認した。

Study on Performance of Semi-Active Base-Isolation System Using Earthquake Observation Records

Nagashima, I., Maseki, R., Shinozaki, Y., Toyama, J., and Kohiyama, M.

Research paper (international conference proceedings), Joint Work

11階建て大学校舎ならびに26階建て超高層建物（それぞれ2005年4月と2008年2月に竣工）にセミアクティブ免震システムを適用した。免震層の層間変位を比較的小さく保ちつつ加速度応答を低減するため，双線形最適制御理論に基づき減衰力の時間遅れを考慮したスライディングモード制御を設計した。大地震時にもシステムの高い信頼性を確保するため，装置の故障を検知するモニタリング装置を導入した。2011年東北地方太平洋沖地震の観測記録と疑似三次元モデルを用いたシミュレーションによりシステムの性能を検証し，セミアクティブ制御の信頼性と性能を明らかにした。

Comparative Study on Cooperative Decentralized Control of a Building-Elevator System Using Linear Quadratic Regulator

Minako YOSHIDA and Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 77 ( 675 ) 705-714 2012.05

Research paper (scientific journal), Joint Work, Accepted

When both a building and its equipment have a vibration controller, an equipment's controller should consider the behavior of a building. First control schemes are classified according to the amount of state variables communicated between the controllers and type of control objectives. Then, a high-rise building with an elevator system under seismic excitation is analyzed to compare the performance of the classified schemes that uses the linear quadratic regulator. It is observed that the story drift and the response of elevator rope can be reduced sufficiently even if all the state variables are not communicated.

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Simultaneous Optimization of Structural and Control Systems of a SDOF Building with a Linear Quadratic Regulator Controller Aiming at Performance-Based Design

Chihiro HORIGUCHI and Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 77 ( 675 ) 715-722 2012.05

Research paper (scientific journal), Joint Work, Accepted

A simultaneous optimization procedure is formulated in order to match desired performances of a building. Design variables of structural and control parts of a building with a linear quadratic regulator (LQR) controller are optimized simultaneously. The natural period and the damping factor of the LQR-controlled system are calculated based on eigenvalue analysis. Design response spectra are used to consider input ground motion and to calculate the maximum control force as well as maximum responses. As an example, this optimization procedure is applied to the seismic strengthening of a traditional wooden building by considering reduction of its displacement and acceleration responses.

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Study on Performance of Semi-Active Base-Isolation System Using Earthquake Observation Records

Nagashima, I., Maseki, R., Shinozaki, Y., Toyama, J., and Kohiyama, M.

Proc. 9th International Conference on Urban Earthquake Engineering & 4th Asia Conference on Earthquake Engineering Joint Conference (the Center for Urban Earthquake Engineering, Tokyo Institute of Technology) 1769 - 1775 2012.03

Research paper (international conference proceedings), Joint Work

Experimental Research of Seismic Response Control of Building-Elevator System Using Linear Quadratic Gaussian Controller

Watanabe, K., Miura, N., Kohiyama, M., and Takahashi, M.

Research paper (international conference proceedings), Joint Work

Damage to elevator rope has been reported in several past earthquakes. To mitigate elevator rope damage, a control method is proposed using a vibration control device designed for a building, e.g. active mass damper (AMD). The method is based on the Linear Quadratic Regulator (LQR) control and aims to achieve the safety of both a building and elevator rope. To demonstrate the effectiveness of the method, an experiment is conducted using a 4-story aluminum specimen, which is a scaled model of a high-rise building; elevator rope is modeled by a copper plate. As a vibration control device for a building, an AMD is settled on the top of the specimen. A vibration control experiment is carried out and it is verified that the proposed method can reduce the response of the elevator rope effectively.

Vibration Control Method for a Building Structure-Equipment System to Reduce Both Structural and Functional Damages

Miura, N. and Kohiyama, M.

Research paper (international conference proceedings), Joint Work

During an earthquake, it is important to maintain the normal functions of a building to facilitate emergency responses and business continuity. Even if a building has no seismic damage, damage to equipment in the building may cause difficulties in providing medical services, performing production operations, or dwelling. Recently, seismic damage to equipment has been reported. Until now, vibration control devices have been devised and installed in many buildings and equipment such as medical and manufacturing devices. A centralized control of these vibration control systems would increase their effectiveness and efficiency. In this paper, we propose a harmonically structured vibration control method for a coupled system consisting of a building and equipment. First, we describe a method for constructing an evaluation function on the basis of the prescribed control objectives and the required performance levels of a building and equipment. Second, decentralized and centralized control systems are developed. Finally, the effectiveness of these two methods is verified on the basis of time-history analysis.

Health Disturbance of Residents in a House with Liquefaction Damage in Mihama Ward, Chiba City

Keino, C. and Kohiyama, M.

International Symposium on Engineering Lessons Learned from the Giant Earthquake (Japan Association for Earthquake Engineering, Architectural Institute of Japan, Japan Society of Civil Engineers, Japanese Geotechnical Society, The Japan Society of Mechanical Engineers, and Seismological Society of Japan) 871 - 882 2012.03

Research paper (international conference proceedings), Joint Work

The 2011 earthquake off the Pacific coast of Tohoku triggered liquefaction of soil in wide areas, particularly at the landfill in Kanto area. There were many residents who complained about health disorders caused by a tilted house due to liquefaction. We carried out a questionnaire survey to residents in Mihama Ward, Chiba City on earthquake damage to their house, health disturbance, etc., and constructed models of health disturbance in terms of tilt angle. It is clarified that the number of residents who suffer insomnia significantly increases when the tilt angle exceeds 1/100 rad.

Seismic Response Analysis of a Semi-Active-Controlled Base-Isolated Building During the 2011 Great East Japan Earthquake

Nakajima, K., Giron, N., Kohiyama, M., Watanabe, K., Yoshida, M., Yamanaka, M., Inaba, S., and Yoshida, O.

Research paper (international conference proceedings), Joint Work

The dynamic properties are examined for a university building with a semi-active base isolation system during the 2011 Great East Japan earthquake. First, the natural periods, damping factors, and mode shapes are identified using an ARX model and the N4SID method based on the observation records of the main shock of this earthquake, in which the building performed as a passive base isolation system due to a maintenance work. Then, the stiffness and damping coefficients of the building are identified using the same records. Finally, the performances of the semi-active base isolation system are analyzed using an aftershock record based on a response simulation of the identified model.

VIBRATION CONTROL OF A BUILDING-ELEVATOR SYSTEM USING FREQUENCY SHAPING AND VARIABLE GAIN FEEDBACK AIMING AT FUNCTION MAINTENANCE

Masayuki KOHIYAMA and Toshimitu BABA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 76 ( 670 ) 2059-2067 2011.12

Research paper (scientific journal), Joint Work, Accepted

A method is proposed to control seismic response of a high-rise building considering function maintenance of an elevator. When a cost function for optimal control is formulated to reduce response of rope, response of a building deteriorates especially in high frequency range. In order to overcome this drawback, the proposed method employs frequency shaping linear quadratic Gaussian control and variable gain feedback. Time history analysis is carried out using simulated ground motion and it is verified that the proposed method can reduce the response of both a building and rope effectively.

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VARIABLE GAIN FEEDBACK CONTROL OF A HIGH-RISE BUILDING-ELEVATOR SYSTEM ADJUSTED TO GROUND MOTION INTENSITY AND RESPONSE LEVEL

Nanako MIURA and Masayuki KOHIYAMA

日本建築学会構造系論文集 (日本建築学会) 76 ( 670 ) 2069-2076 2011.12

Research paper (scientific journal), Joint Work, Accepted

A control method is proposed based on frequency shaped LQG and variable gain feedback in order to choose proper control objective and prevent saturation of control force considering intensity of ground motion and level of building response. The controller examines exceedance rate of building response over a threshold and the maximum required control force estimated from ground acceleration in order to reduce response of both a building and elevator rope efficiently preventing saturation. It is demonstrated that the proposed method can suppress unpreferable response of building layers near the top induced by control force.

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Large-Scale FE Analysis of Steel Building Frames Using E-Simulator

Miyamura, T., Ohsaki, M.,Kohiyama, M. , Isobe, D., Onda, K., Akiba, H., Hori, M., Kajiwara, K., and Ine, T.

Progress in Nuclear Science and Technology (Atomic Energy Society of Japan) 2 651-656 2011.10

Research paper (scientific journal), Joint Work, Accepted

The results of a high-precision finite element (FE) analysis using the E-Simulator, which is a parallel FE analysis software package for virtual shaking-table tests of civil or architectural structures, are presented for the seismic responses of a 4-story steel frame and a 31-story super-high-rise steel frame. The 4-story frame is a specimen of the full-scale total collapse shaking-table test conducted in 2007 at the Hyogo Earthquake Engineering Research Center of the National Research Institute of Earth Science and Disaster Prevention, Japan. These steel frames are modeled by meshes of hexahedral solid elements. Large strain elastoplasticity is considered in the analyses. It is shown through numerical examples that elastoplastic dynamic responses can be estimated with good accuracy without resorting to macro models such as those involving plastic hinge and composite beam effects.

Study on Performance of Semi-Active Base-Isolation System Using Earthquake Observation Records

Nagashima, I., Maseki, R., Shinozaki, Y., Toyama, J., and Kohiyama, M.

International Symposium on Disaster Simulation and Structural Safety in the Next Generation (Graduate School of Simulation Studies, University of Hyogo) 1 - 7 2011.09

Research paper (international conference proceedings), Joint Work

A semi-active base-isolation system using semi-active hydraulic dampers was installed in an 11-storey university building and a 26-storey super high-rise building that were completed in Tokyo in April 2005 and February 2008, respectively. Sliding mode control considering the time lag of the damper force was designed based on a bilinear optimal control theory to reduce the acceleration response of the buildings, while keeping the deformation of the isolation story relatively small. A monitoring system was also applied to detect the malfunctions of the whole system, including the computer, the sensors, the electromagnetic valves of the dampers, etc. The monitoring system helps the semi-active base-isolation system to be certified as highly reliable system that offers continued control even in the event of a major earthquake. This paper discusses the performance verification of the semi-active base isolation system through earthquake observation records. Seismic response analyses using a pseudo three-dimensional model of the buildings were also conducted to simulate the responses observed in the 2011 off the Pacific coast of Tohoku Earthquake. The reliability and performance of the semi-active control was thereby clarified.

Finite Element Model of Steel-Concrete Composite Beam for High-Precision Seismic Response Analyses of Four-Story Steel Frame

Yamashita, T., Ohsaki, M., Miyamura, T., Kohiyama, M., and Zhang, J.-Y.

International Symposium on Disaster Simulation and Structural Safety in the Next Generation (Graduate School of Simulation Studies, University of Hyogo) 1 - 5 2011.09

Research paper (international conference proceedings), Joint Work

鋼・コンクリート合成梁の高精度有限要素解析のためのモデル化方法と数値解析手法について示した。まず，鋼材の構成則について区分線形・複合硬化則を用い改良した。本構成則は繰り返し載荷を受ける片持梁の荷重・変形関係により検証を行った。本構成則により，非対称な変形応答が精度よく模擬できることが示された。次に，鋼材の梁・柱，鉄筋コンクリートのスラブは六面体一次要素に離散化し，柱により支持された合成梁の詳細なモデルを構築した。このモデルを用いた静的繰り返し載荷のシミュレーションの結果を報告した。

E-Simulator Virtual Shaking-Table Test: Comparative study on elastoplastic dynamic responses of super-highrise steel frame between virtual shaking-table test using e-simulator and beam element analysis

Kohiyama, M., Miyamura, T., Isobe, D., Ohsaki, M., Onda, K., Hori, M., Akiba, H., Kajiwara, K., and Ine, T.

6th European Conference on Steel and Composite Structures (Eurosteel 2011) (Budapest University of Technology and Economics, University of Miskolc, and University of Pécs) B 1113 - 1118 2011.09

Research paper (international conference proceedings), Joint Work

A virtual shaking-table test of a 31-story high-rise office building has been carried out using the E-Simulator. The model consists of solid elements and the result of the E-Simulator analysis was compared with that of the beam element analysis based on the ASI-Gauss technique. Consequently, the response difference between the E-Simulator models and the beam element possibly arose from model differences in damping, slabs and modeling error of plastic hinge of the beam element model.

High-Precision FE-Analysis for Collapse Simulation of Steel Frames Considering Composite Beam Effect

Ohsaki, M., Miyamura, T., Kohiyama, M., Zhang, J.-Y., Isobe, D., Onda, K., Yamashita, T., Hori, M., Akiba, H., and Kajiwara, K.

6th European Conference on Steel and Composite Structures (Eurosteel 2011) (Budapest University of Technology and Economics, University of Miskolc, and University of Pécs) B 921 - 926 2011.08

Research paper (international conference proceedings), Joint Work

A high-precision FE-analysis has been carried out for simulating the responses of composite cantilever beam under static cyclic loading. Accuracy of the piecewise linear combined isotropic-kinematic hardening rule for steel material has been first verified using the experimental results of a beam subjected to complex asymmetric deformation.
Computational results show that the strength of the composite beam under positive and negative bending states can be estimated accurately with extended Drucker-Prager model for concrete, rigid beam for stud bolt, and the piecewise linear combined hardening for steel, and contact condition between slab and column. However, crack in concrete should be appropriately modeled for accurate estimation of stiffness in unloading states.
It has also been shown that the elastoplastic dynamic responses of a 4-story steel frame, which was tested in E-Defense, can be simulated within a moderate accuracy using only the constitutive and structural models without resort to a macro model such as plastic hinges and fiber models.

Questionnaire Survey on Health Disturbance of Residents in Mihama Ward, Chiba City who Suffered Housing Damage Due to Liquefaction

Masayuki KOHIYAMA, Chinami KEINO, and Takao SONOBE

Journal of Social Safety Science (Institute of Social Safety Science) 17 145-151 2011.07

Research paper (scientific journal), Joint Work, Accepted

The 2011 off the Pacific coast of Tohoku Earthquake triggered liquefaction of soil in wide areas. In particular, a number of damaged houses were found in the land reclamation areas of the Kanto retion. Some residents living in houses tilted by liqufaction complained of health disorders. We report the result of questionnaire survey of residents in Mihama Ward, Chiba City, about the characteristics of their house, earthquake damage, health disturbances, and so on. Based on the survey data, we construct probability models of health disturbance with respect to house tilt angle investigated by the local government for the certificate of damage. The probability of health disturbance exceeded 50% when the tilt angle was larger than approximately 0.013 rad.

Seismic risk assessment of building-elevator systems based on simulated ground motion considering long period components and phase characteristics

Kohiyama, M. and Kita, T.

Applications of Statistics and Probability in Civil Engineering (Proc. the 11th International Conference on Applications of Statistics and Probability in Civil Engineering (ICASP11)) (CRC Press) 2568-2575 2011.07

Research paper (international conference proceedings), Joint Work, Accepted

An elevator in a high-rise building causes a problem of elevator rope sway. To address this problem, it is necessary to understand the relation between responses of a building and rope. In this study, earthquake ground motions are synthesized with a newly proposed simple method to construct a Fourier phase spectrum. The response of a building-elevator system is obtained using a response spectrum and complex eigenvectors, which can consider non-proportional damping. Seismic risk of elevator rope is evaluated for 50, 100, 150, 200 and 250-meter-high buildings. As a result, the probability of rope damage changes significantly depending on the height of a building and an elevator car position. It is recommended to move and park an elevator car at low risk positions when few people use the elevator such as in nighttime.

High-Precision FE-Analysis for Seismic Collapse Simulation of Steel Building Frames

Yamashita, T., Miyamura, T., Ohsaki, M., Kohiyama, M., Isobe, D., Onda, K., Hori, M., Zhang, J.-Y., Akiba, H., and Kajiwara, K.

3rd International Conference on Computational Methods in Structural Dynamics & Earthquake Engineering (COMPDYN 2011) (International Association for Computational Mechanics (IACM)) 10 2011.05

Research paper (international conference proceedings), Joint Work

The project of E-Simulator is under way at Hyogo Earthquake Engineering Research Center (E-Defense), which belongs to National Research Institute for Earth Science and Disaster Prevention (NIED), Japan. E-Defense facilitates the world’s largest shaking table. The E-Simulator uses the parallel EF-analysis software package called ADVENTURECluster (ADVC) as a platform, and we carried out elastoplastic seismic response analysis of high-rise building frame with over 70-million DOFs. In this study, we report the results of high-precision FE-analysis for simulation of dynamic collapse behavior of the 4-story steel building frame. The whole frame is discretized into hexahedral elements with linear interpolation functions. In order to improve the accuracy of collapse simulation, a new piecewise linear combined isotropic and kinematic hardening rule is implemented for steel material, and its parameters are identified from the uniaxial material test result. The stud bolts are precisely modeled using multipoint constraints and nonlinear springs. The wire-meshes in the concrete slab are modeled using hexahedral elements. The damping due to plastic energy dissipation of exterior walls is modeled by shear springs between the floors. The accuracy of the model is verified in comparison to the physical test of steel-concrete composite beam subjected to static deformation. It will be shown that elastoplastic dynamic responses of the 4-story frame can be estimated with good accuracy using a high-precision FE-analysis without resort to macro-models such as plastic hinge and composite beam effect.

Probabilistic Evaluation of Retrofitting Priority of Houses　Using a Model of Evacuation Route Selection under Road Blockade

Saki MAEDA and Masayuki KOHIYAMA

Journal of Social Safety Science (Institute of Social Safety Science) 14 8-15 2011.03

Research paper (scientific journal), Joint Work, Accepted

We propose a new method to evaluate quantitatively the effectiveness of retrofitting of houses for evacuation. A model of evacuation route selection under road blockade is constructed based on a subject experiment and built it into an agent model for evacuation simulation. The priority of houses that should be retrofitted is probabilistically evaluated. Because evacuation behavior is considered, this method can appropriately identify houses that should be retrofitted. An index is newly introduced to evaluate retrofitting priority of houses quantitatively using improvement ratio of number of evacuees in a unit time. The proposed method can show retrofitting priority of houses effectively when the ground motion intensity is assumed as JMA Seismic Intensity 6 upper.

Seismic Risk Assessment of Building-Elevator System with Non-Proportional Damping Using Complex Complete Quadratic Combination Method

Tetsuya KITA and Masayuki KOHIYAMA

AIJ Journal of Technology and Design (Architectural Institute of Japan) 16 ( 34 ) 883-888 2010.10

Research paper (scientific journal), Joint Work, Accepted

An elevator set up in a high-rise building may cause a problem of elevator rope sway. To solve this problem, the responses of building-elevator systems are examined based on the Complex Complete Quadratic Combination method and damage risk is evaluated with respect to possible earthquakes in Chuetsu district of Niigata Prefecture and the northwestern part of Chiba Prefecture. It is observed that some positions of elevator car can reduce the damage risk of main rope by shifting the natural periods of the rope away from the natural periods of the building.

Access to Document (DOI)

Evaluation of Seismic Damage Risk of Elevator Rope in High-Rise Building Based on CCQC Method

Kohiyama, M., Kita, T., and Mitsui, A.

9th U.S. National and 10th Canadian Conference on Earthquake Engineering (Earthquake Engineering Research Institute & Canadian Association for Earthquake Engineering) 10 2010.07

Research paper (international conference proceedings), Joint Work, Accepted

To solve the problem of elevator rope sway in a high-rise building, the seismic damage risk of a building and suspension rope are examined using the Complex Complete Quadratic Combination method. A building site was assumed at Sinjuku, Tokyo in Japan and possible earthquake source zones were considered in Chuetsu, Niigata and the northwest of Chiba. The following findings were obtained: For the 100-, 150- and 250-meter-high buildings, the damage risk of the rope was high when an elevator car or a counterweight was in a lower floor because the rope was long to cause resonance. However, for the 50-, 100- and 200-meter-high buildings, the damage probability was the highest when in a layer other than the bottom. The distribution of the probability of rope damage varies considerably depending on the building height.

Dynamic Property Evaluations of Full-Scale 4-Story Steel Frame Using Parallel FE-Analysis

Kohiyama, M., Ohsaki, M., Miyamura, T., Onda, K., Isobe, D., Akiba, H., Hori, M., Kajiwara, K., and Ine, T.

9th U.S. National and 10th Canadian Conference on Earthquake Engineering (Earthquake Engineering Research Institute & Canadian Association for Earthquake Engineering) 9 2010.07

Research paper (international conference proceedings), Joint Work

The project of E-Simulator is under way at Hyogo Earthquake Engineering Research Center (E-Defense) of National Research Institute of Earth Science and Disaster Prevention (NIED), Japan, which facilitates the world's largest shaking table. The E-Simulator uses the parallel finite element (FE) analysis software package called ADVENTYRECluster (ADVC) as a platform. In this study, we report the results of high-precision FE-analysis for simulation of collapse behavior of the 4-story steel building frame that is the specimen of the full-scale total collapse shaking-table test conducted in September 2007 at E-Defense. It is shown that elastoplastic dynamic responses can be estimated with good accuracy using a high-precision FE-analysis without resort to macro models such as plastic hinge and composite beam effect.

Large-Scale Parallel Analysis System for Virtual Shaking Test for Steel Building Frames

Akiba, H., Ohsaki, M., Miyamura, T., Kohiyama, M., Onda, K., Isobe, D., Hori, M., Kajiwara, K., and Ine, T.

9th World Congress on Computational Mechanics and 4th Asian Pacific Congress on Computational Mechanics (WCCM/APCOM 2010) (International Association for Computational Mechanics) 308 2010.07

Research paper (international conference proceedings), Joint Work

Introduction: In structural analysis, the iterative substructuring method is a most promising framework, which is to be used on parallel computer systems. But using just the parallel processing does not allow us to obtain the desired level of performance. We need special preconditioning procedures well-suited to the iterative method and the domain decomposition method. The CGCG method [1], which will be described in some detail in this paper, gives high performance to the iterative substructuring method by a precondition technique depending on the domain decomposition. The CGCG method is implemented in a commercial code ADVENTURECluster (ADVC), and ADVC can solve dynamic nonlinear problems with more than 10 million degrees of freedom. Hyogo Earthquake Engineering Research Center (E-Defense) owns the world’s largest shaking table [2]. Also E-Defense is developing E-Simulator code which we hope to act as a virtual shaking table by fully taking advantage of recent development of high-performance computing. E-Simulator uses ADVC as a platform. The paper shows the results of a nonlinear seismic analysis of steel building frames as a test specimen of the virtual shaking table. Numerical Algorithms and Examples: The CGCG method is a fully iterative method based on the domain decomposition method, in which the decomposed subdomains are not considered as substructures, whereas the standard iterative substructuring methods take those as substructures. Recent enhancement of the preconditioning gave the method higher performance than the original CGCG method. The enhanced CGCG method and E-simulator equipped with the enhanced CGCG method are applied to solve nonlinear seismic analyses of steel building frames. Conclusions: The enhanced CGCG method is described, and the E-simulator equipped with the enhanced CGCG method is applied to analyze nonlinear seismic analyses of steel building frames, which will be examples of the virtual shaking test. References: [1] Akiba et al, Proceedings of SC06. [2] http://www.bosai.go.jp/hyogo/ehyogo/.

Large-Scale Parallel FE-Analysis for Simulation of Collapse Behavior of Steel Building Frames

Miyamura, T., Ohsaki, M., Kohiyama, M., Onda, K., Isobe, D., Akiba, H., Hori, M., Kajiwara, K., and Ine, T.

9th World Congress on Computational Mechanics and 4th Asian Pacific Congress on Computational Mechanics (WCCM/APCOM 2010) (International Association for Computational Mechanics) 308 2010.07

Research paper (international conference proceedings), Joint Work

Introduction: The project of E-Simulator is under way at Hyogo Earthquake Engineering Research Center (E-Defense) of National Research Institute of Earth Science and Disaster Prevention (NIED), Japan, which facilitates the world's largest shaking table (Hori et al. 2007).The E-Simulator uses ADVENTYRECluster (ADVC)/ADVENTURE as a platform (Akiba et al. 2006, Ohsaki et al. 2009). ADVC is a commercial software package of parallel finite element (FE) analysis that uses the domain decomposition technique for parallel implementation. ADVENTURE is an open source version, which is a prototype of ADVC. ADVC can solve dynamic nonlinear problems with more than 10 million DOFs for a structure discretized by three-dimensional solid elements. The E-Simulator is conceived as a virtual shaking table, and its final form is a software environment to simulate global and local seismic responses of a city, as assemblage of buildings and infrastructures, by fully taking advantage of recent development of computer science and high-performance computing in computational mechanics. Analyses of Steel Building Frames: As a part of this project, the purpose of this study is to show that the global and local elastoplastic behaviors of steel frames under severe seismic motions can be simultaneously simulated by a high-precision FE-analysis software, E-Simulator. Elastoplastic dynamic analyses are carried out for a 31-story high-rise steel building model and for the 4-story frame model that models the specimen of full-scale shaking-table test conducted at E-Defense shaking-table facility. The whole structures are discretized using hexahedral solid elements without resort to macro models such as plastic hinge and composite beam effect. Conclusion: It is shown that E-Simulator can simulate the large-strain elastoplastic dynamic behaviors of the steel building frames. Both global and local behaviors of the structures are estimated accurately by the simulation using fine meshes with the solid elements. References: Hori et al., Journal of Earthquake Engineering 29, 1420-1425, 2007 (in Japanese) Akiba et al., Proc. of SC06, 2006 Ohsaki et al., EESD, 38, 635-654, 200.

Form Finding Analysis Based on Variational Method for Multistable Structure Utilizing Snap-Through Behaviour

Kurokawa, T., Shigematsu, M., and Kohiyama, M.

9th World Congress on Computational Mechanics and 4th Asian Pacific Congress on Computational Mechanics (WCCM/APCOM 2010) (International Association for Computational Mechanics) 10 2010.07

Research paper (international conference proceedings), Joint Work

This study proposed a multistable structure using snap-through behavior as an adaptable structure, which can change its size and transform its configuration easily. To know the stable configuration and stress of the structure, the form finding analysis method of the structure is formulated. Then, a design support system is proposed based on a calculation method of required forces to transform its configuration. Finally, several configurations are demonstrated with a small scale model to show the adaptability and feasibility of the proposed structure.

Frequency Shaping and Variable Gain Feedback to Control Seismic Response of a Building and Elevator Rope

Kohiyama, M. and Baba, T.

5th World Conference on Structural Control and Monitoring (International Association for Structural Control and Monitoring) 8 2010.07

Research paper (international conference proceedings), Joint Work

This paper first clarifies the vibration characteristics of elevator rope in a high-rise building with a response control system such as active mass damper and linked structures. When a cost function for optimal control is formulated to reduce distance between a building and rope, response of the building deteriorates especially in high frequency range. In order to overcome this drawback, a control method is proposed based on frequency shaping linear quadratic Gaussian and variable gain feedback. Time history analysis is carried out using simulated ground motion and it is verified that the proposed method can reduce the response of both a building and rope effectively.

Simultaneous Optimal Design of Structural and Control Systems of a Building under Seismic Excitation Using a Design Response Spectrum

Horiguchi, C. and Kohiyama, M.

6th China-Japan-Korea Joint Symposium on Optimization of Structural and Mechanical Systems (Japan Society of Mechanical Engineers & International Society for Structural and Multidisciplinary Optimization) 5 2010.06

Research paper (international conference proceedings), Joint Work

A simultaneous optimization method is proposed for a structural system controlled by a least quadratic regulator (LQR) under seismic excitation. An LQR-controlled system is converted into an equivalent uncontrolled structural system and the natural period and the damping factor are derived. A design response spectrum is used to consider input earthquake motion and the maximum response and control force of the system are calculated based on the spectrum. Simultaneous optimization consists of the following two stages: 1) feasible region of design variables are evaluated; 2) the objective function of the cost of the total system is minimized. A single mass structure with LQR controller is simultaneously optimized as a numerical example.

Parallel FE-Analysis for Collapse Simulation of 4-Story Steel Building Frame

Miyamura, T., Ohsaki, M., Kohiyama, M., Onda, K., Isobe, D., Akiba, H., Hori, M., Kajiwara, K., and Ine, T.

Joint Conference Proceedings of 7th International Conference on Urban Earthquake Engineering (7CUEE) & 5th International Conference on Earthquake Engineering (5ICEE) (Center for Urban Earthquake Engineering, Tokyo Institute of Technology) 887-892 2010.03

Research paper (conference, symposium, etc.), Joint Work

The results of high-precision FE-analysis is presented for simulation of collapse behavior of the 4-story steel building frame that is the specimen of the full-scale total collapse shaking-table test conducted in September 2007 at E-Defense. The computation is carried out using the E-Simulator, which is under development at Hyogo Earthquake Engineering Research Center (E-Defense) of National Research Institute of Earth Science and Disaster Prevention (NIED), Japan. The E-Simulator uses the parallel finite element (FE) analysis software package called ADVENTYRECluster (ADVC) as a platform. It is shown through numerical examples that elastoplastic dynamic responses can be estimated with good accuracy using a high-precision FE-analysis without resort to macro models such as plastic hinge and composite beam effect.

Seismic Response Control of a Building and Elevator Rope with Active Mass Damper

Baba, T. and Kohiyama, M.

Theoretical and Applied Mechanics Japan (National Committee for IUTAM, Science Council of Japan) 58 19-30 2010.02

Research paper (scientific journal), Joint Work, Accepted

Elevator rope-sway is a serious problem for a high-rise building under seismic excitation. Vibration control of the rope-sway using active mass damper (AMD) is investigated, which is usually designed simply for control of building response. The linear quadratic regulator (LQR) is employed as the AMD control system. Numerical simulations are conducted and the responses are analyzed in both frequency and time domains. The relative displacement between the building and the rope is evaluated as well as the story drift and the absolute acceleration of the building. It is observed that the control method considering the rope-sway can effectively decrease response of the rope after seismic excitations.

Effect of Spatially Random Ground Motions on a One-Story Wooden Building Considering stiffness of Horizontal Diaphragm

Nanako MIURA and Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 74 ( 645 ) 1975-1982 2009.11

Research paper (scientific journal), Joint Work, Accepted

This paper studies the effect of spatially random ground motions on the seismic response of a one-story multi-span wooden building considering the stiffness of the horizontal diaphragms. The deformation angles at columns and horizontal diaphragms are examined using time history response analyses with simulated input motions. It is shown that stiffness increase of the horizontal diaphragms and dimensions increase of the building make responses large to damage, and that large responses at the horizontal diaphragms are much more serious than at columns.

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A Comparative Study on Equivalent Linear Model to Assess Occurrence of Building Damage

Niikawa, Y. and Kohiyama, M.

10th International Conference on Structural Safety and Reliability (International Association for Structural Safety and Reliability) 3167-3174 2009.09

Research paper (conference, symposium, etc.), Joint Work, Accepted

This study investigates equivalent linear models which can assess occurrence of building damage with high accuracy for several threshold values. The accuracy of the following three equivalent linear models are examined: 1) the conventional model of which stiffness of all the story is determined based on seismic story shear force, 2) the shear-force-equivalent model of which equivalent stiffness of the first story is determined based on seismic story shear force, and 3) the energy-equivalent model of which equivalent stiffness of the first story is determined based on earthquake input energy. The equivalent damping is obtained from input energy of earthquake motion using nonlinear models. As a result, the most accurate equivalent linear model is the shear-force-equivalent model.

Large Scale Parallel Structural Analysis System and Its Application to Nonlinear Seismic Analysis of High Rise Building Frames

Akiba, H., Ohsaki, M., Miyamura, T., Kohiyama, M., Isobe, D., Hori, M., Kajiwara, K., and Ine, T.

Chinese Congress of Theoretical and Applied Mechanics 2009 (The Chinese Society of Theoretical and Applied Mechanics) 280-292 2009.08

Research paper (international conference proceedings), Joint Work

様々な工業製品の設計解析において，大規模構造計算は重要で現実的なツールになりつつある。有限要素解析における解析の並列化の困難は克服されつつあり，近年の高性能計算機を有効活用できるようになってきている。兵庫耐震工学研究センターの数値震動台（E-シミュレーター）は，解析コードADVENTUREClusterをプラットフォームとしており，コースグリッド共役勾配法を用いた並列解析により陰解法による大規模構造解析を可能にした。これを用いた31層超高層建物の地震応答解析の事例を報告した。

Vulnerability Functions for Wooden Buildings Using A Probability Distribution Model of seismic Performance

Masayuki KOHIYAMA and Masashi SHIOMI

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) 74 ( 640 ) 1029-1036 2009.06

Research paper (scientific journal), Joint Work, Accepted

Vulnerability functions for wooden buildings are proposed, which employ a probability distribution model of seismic performance. An acceleration response spectrum is used as input to the functions. The probability distribution model is formulated based on two indices of seismic diagnosis data: stiffness and resistance force, and it is clarified that the bivariate normal distribution is a reliable model. Regarding estimation accuracy, the proposed functions are compared with experience-based vulnerability functions in past literature for three earthquake disasters. The proposed functions indicate fairly good accuracy when proper parameters of stiffness increase and resistance force increase due to non-structural walls are used.

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High-precision finite element analysis of elastoplastic dynamic responses of super-high-rise steel frames

Ohsaki, M., Miyamura, T., Kohiyama, M., Hori, M., Noguchi, H., Akiba, H., Kajiwara, K., and Ine, T.

Earthquake Engineering and Structural Dynamics (John Wiley & Sons) 38 ( 5 ) 635-654 2009.04

Research paper (scientific journal), Joint Work, Accepted

A new framework is presented for analysis of dynamic collapse behavior of steel frames using large-scale parallel finite element method based on the domain decomposition method. The analysis software is based on ADVC as a part of the E-Simulator that takes advantage of recent development of computer science and high-performance parallel computing in computational mechanics. By making an analysis model with fine meshing, a complicated sequence of local buckling of columns and beams can be simulated. Numerical results are shown for dynamic collapse analysis of single-story and 5-story frame models to show that the global and local behaviors are simultaneously simulated by a high-precision finite element analysis. Eigenvalue analysis is also carried out for a 31-story frame to demonstrate that dynamic analysis can be carried out for a structure discretized to solid elements with more than 70 million DOFs.

Incentives and Disincentives Analysis for Improving Policy for Seismic Risk Management of Homeowners in Japan

Masayuki Kohiyama, Anne S. Kiremidjian, Kimiro Meguro, Miho Yoshimura Ohara

Natural Hazards Review (American Society of Civil Engineers) 9 ( 4 ) 170-178 2008.11

Research paper (scientific journal), Joint Work, Accepted, ISSN 15276988

In order to improve policy and programs to promote retrofitting of houses in Japan, incentives and disincentives for seismic risk management by homeowners were studied by two approaches: a fault tree analysis (FTA) method and a questionnaire survey to homeowners. The result of the FTA revealed two common causes that hindered homeowners’ seismic risk management: disaster awareness problem and fear of dishonest contractors. The questionnaire survey identified both incentives and disincentives. It was observed that neighbors could prompt retrofitting statistically significantly, and there were three major disincentives to retrofitting: high retrofitting cost, low contractor credibility, and little engineering information. The current policy in Japan put emphasis on seismic diagnosis in comparison with those in the United States. However, based on the above-mentioned observations, it was suggested that planning and reviewing of retrofitting work, as well as management after retrofitting, should be assisted more comprehensively in order to promote retrofitting. In addition, more attention should be paid to risk communication to provide engineering information on retrofitting, to foster mutual trust between homeowners and contractors/engineers, and to encourage information exchange with neighbors.

Vulnerability Functions for Wooden Houses Based on Seismic Diagnosis Data and Equivalent Linear Models

Kohiyama, M., Shiomi, M.

14th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 8 2008.10

Research paper (international conference proceedings), Joint Work

Vulnerability functions of wooden houses, which use the results of seismic diagnosis and an acceleration response spectrum, are formulated using equivalent linear models. They employ a probability density function of seismic performance indices of wooden houses, which are separated into an index of the resistance force and other indices related to the degradation of resistance force. The input seismic motion is evaluated based on an acceleration response spectrum and a natural period is determined by the indices of resistance force and threshold of damage. The application results to the 1995 Hyogo-ken Nanbu earthquake are compared with the damage statistics at the five sites, which have seismic records. The estimated damage ratios coincide fairly well with the actual damage surveyed by local governments.

Development of Extremely Large-Scale Analysis Software (E-Simulator: Virtual Shaking Table) for Earthquake Dynamic Collapse Analysis of Structures

Ine, T., Hori, M., Noguchi, H., Ohsaki, M., Miyamura, T., Oguni, K.， Kohiyama, M., Kajiwara, K., and Akiba, H.

14th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 8 2008.10

Research paper (international conference proceedings), Joint Work

This report presents a research project of developing “E-Simulator: virtual shaking table”, which is 　a simulation software based on a finite element method to analyze non-linear seismic response of constructions, as a part of E-Defense project. The key features of E-Simulator are 1) extremely large-scale numerical computation that realizes the finest temporal and spatial resolution of the structure response and 2) simulation of collapsing processes of structures that is comparable with the 3D full-scale model earthquake tests of E-Defense. This report explains the objectives of the E-Simulator and its two features. It also introduces the current state of E-Simulator project which includes the earthquake dynamic collapse analysis of 31-story steel framed structure and particle discretization scheme FEM for the RC structure.

Examination of a Simple Ground Model to Estimate Local Seismic Waves in an Irregular Ground Area

Horiike, M., Tagawa, S. and Kohiyama, M.

14th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 8 2008.10

Research paper (international conference proceedings), Joint Work

Accuracy of estimated seismic waves using a one-dimensional ground model is examined. Hiyoshi Area in Yokohama is focused, which has relatively complicated topography. First, two one-dimensional layered ground models are prepared: Model 1, a four-layered model based on a boring log and Model 2, a two-layered model based on airborne laser profiler and geological cross sections. Seismic records with peak ground acceleration 8 to 141 cm/s2 are used for analysis, which were observed by six seismic stations in the study area. Incident waves at bedrock level of each observation point are calculated by one-dimensional equivalent linear analysis. Two ground models are compared with respect to acceleration response spectra. Then, acceleration response spectra at bedrock level at each observation point are compared in regard to each earthquake event. The results suggest that it is necessary to increase the spatial density of bedrock data to make an accurate ground model and to consider influence of surface waves and oblique incidence in regard to the studied area.

Damage Detection of a Reinforced Concrete Beam Based on Fourier Spectrum of Response to Impact Excitation

Sano, A., Kumagai, Y. and Kohiyama, M.

Theoretical and Applied Mechanics Japan (National Committee for IUTAM, Science Council of Japan) 56 77-85 2008.01

Research paper (scientific journal), Joint Work, Accepted

In order to develop damage detection method for a reinforced concrete (RC) structure using an impact hammer excitation, some indices based on Fourier spectrum of a response accelerogram were analyzed. Two test pieces of a RC beam were used: one has sufficient shear reinforcement and the other not. To cause nine stages of damage, a test piece was simply supported and vertical downward forces were loaded. At each damage stage, an impulse excitation was applied and the response acceleration was measured. It was revealed that an index using phase difference spectrum showed fairly good correlation with damage by which bending stiffness was reduced although the index used no information on excitation force. Between the two test pieces, clear difference of the correlation was not observed possibly because bending cracks proceeded for both test pieces.

Isolator Level in Height of Seismic Isolation System with Semi-Active Control

Yamamura, T. and Kohiyama, M.

Theoretical and Applied Mechanics Japan (National Committee for IUTAM, Science Council of Japan) 56 153-163 2008.01

Research paper (scientific journal), Joint Work, Accepted

Recently, buildings with an isolation device installed in middle story have been constructed. However, an adequate isolation layer level in height of a mid-story isolated building has not been established, and this causes a restriction on design of a plan of a mid-story isolated building. To reduce this restriction, semi-active controlled systems are compared to observe response characteristics. Regarding a control law, velocity feedback based on bilinear optimal control is used. Based on time history analysis with a 30-DOF system, response differences with respect to a position of an isolation layer is studied. It is observed that semi-active control scheme can be used to reduce the absolute acceleration of a roof and the deformation of an isolation layer. On the other hand, much attention must be paid to behavior of a lower structure under seismic excitation in design.

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Vulnerability Functions Using Seismic Diagnosis Data Extended by Equivalent Linear Models

Masashi SHIOMI and Masayuki KOHIYAMA

AIJ Journal of Technology and Design (Architectural Institute of Japan) 13 ( 26 ) 481-486 2007.12

Research paper (scientific journal), Joint Work, Accepted

It is important to establish an accurate vulnerability function to estimate seismic damage. The purpose of this study is to expand vulnerability functions of wooden buildings using seismic diagnosis data based on equivalent linear models. The vulnerability functions consider characteristics of the region such as ground and building characteristics. The paper describes a method to calculate ratio of building damage in a region. The accuracy of the method is verified using the damage data of the Great Hanshin-Awaji Earthquake Disaster.

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Questionnaire Survey on Effective Explanation of Seismic Capacity of Houses (Part 2. Effectiveness of Probability-Based Explanation)

Sasaki, K., and Kohiyama, M.

2nd International Conference on Urban Disaster Reduction (Disaster Management Society of Taiwan, National Science and Technology Center for Disaster Reduction, and National Taiwan University) 9 2007.11

Research paper (international conference proceedings), Joint Work

Effectiveness of probability-based explanation of seismic capacity was investigated based on a questionnaire survey. Dynamic analysis using a two-degree-of-freedom model of a wooden house was conducted to formulate a fragility curve. Then, probability of damage in a certain period was evaluated based on the fragility curve and a seismic hazard curve. An empirical formula of relation between JMA intensity and peak ground velocity was used to evaluate probability of damage under a certain seismic intensity.
About 55% of the respondents answered that probability of damage under a certain seismic intensity was the easiest among presented explanations of seismic capacity, and less than 10% of the respondents chose probability of damage within a certain period as the easiest explanation. In explaining several seismic capacities for comparison, showing only ratio or difference of the probabilities of damage was not as easy to understand as showing each probability value. The respondents had bias of overrated seismic risk first. But a house with high seismic capacity was preferred even after information on proper risk of seismic damage and additional cost to improve seismic capacity were provided. These results suggest that probability of damage is useful to explain seismic capacity of house.

Questionnaire Survey on Effective Explanation of Seismic Capacity of Houses (Part 1. Perceived Risk of Earthquake and Building Collapse)

Kohiyama, M., and Sasaki, K.

Research paper (international conference proceedings), Joint Work

The questionnaire survey was conducted to clarify effective explanation of seismic capacity of houses. The respondents were people who lived in Yokohama City, Kawasaki City or 23 Wards of Tokyo, who wanted home ownership for 20 to 30 years in future, and who were 30 to 49 years old, and 759 valid answers were obtained. Questions regarding seismic risk perception and preference of seismic capacity of a house were asked through a Web page from November 1 to 2, 2006.
It was observed that the respondents overrated seismic risk; about 60% of the respondents thought that they would experience strong ground motion of JMA intensity 7 in future and 85% thought a damaging earthquake would occur within 30 years in their or nearby town. In addition, the respondents underrated performance of a house with higher earthquake resistance grades. Risk of building collapse could be reduced to 1/5 by upgrading from Grade 1 to Grade 2 (1.25 times larger resisting force) and 1/10 from Grade 1 to Grade 3 (1.5 times larger resisting force). However, about 70% of the respondents did not think that the risk could be reduced to the above ratios. These results suggest that preference of seismic performance of a house can be changed by providing reliable risk information.

Effective Explanation of Grades of Seismic Capacity Using Probability of Damage

Sasaki, K. and Kohiyama, M.

Journal of Japan Association of Earthquake Engineering (Japan Association of Earthquake Engineering) 7 ( 6 ) 31-47 2007.11

Research paper (scientific journal), Joint Work, Accepted

The questionnaire survey was conducted to clarify effective explanation of grades of seismic capacity using probability of damage. The panels living in Yokohama City, Kawasaki City or 23 Wards of Tokyo who were in their thirties to forties, and who wanted home ownership were selected and 759 valid answers were obtained. Questions regarding seismic risk perception and preference of seismic capacity of a house were asked. As a result, it was observed that the panels overrated seismic risk and demanded various seismic capacities. Additionally, it was revealed that explanation using the probability of damage in relation to seismic intensity was effective, and that a house with high seismic capacity was preferred even after information on risk of seismic damage, which might remove the bias of the overrated seismic risk, and on additional cost to improve seismic capacity were provided.

Fundamental Study on Building-Elevator System for Reduction of Earthquake Damage to Main Rope

Asami MITSUI and Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 621 ) 41-48 2007.11

Research paper (scientific journal), Joint Work, Accepted

Due to past several earthquakes, damage of elevators, especially in rope, were reported. It is quite important to maintain the function of an elevator for rescue activity after a severe earthquake. This study clarifies the correlation between vibration of a main rope of an elevator and the characteristics of a building (stiffness and damping factor). Influence of the setting position of a driving machine is also investigated. A model of a thirty-story building with elevator system is analyzed on vibration modes and dynamics responses to several seismic ground motions. It is shown that two-elevator system, which sets a transfer floor in the middle height of a building, can reduce the response of a main rope, and that increased damping factor can also reduce the response.

CONSIDERATION FOR PREPARATION OF PROPER PROPOSALS BY ACADEMIC SOCIETIES AND FOR THEIR IMPLEMENTATION

Kimiro MEGURO, Yasunori HADA, Hiroyoshi OSHIMA, Masayuki KOHIYAMA, Shinya KONDO, Mitsuaki SAEKI, Gaku SHOJI, Yoshiaki HISADA, and Miho Yoshimura OHARA

土木学会地震工学論文集 (Japan Society of Civil Engineers) 8 2007.08

Research paper (scientific journal), Joint Work, Accepted

本論文は，大都市圏の地震防災性の向上に資する従来よりも効率的で，かつ，より説得力のある提言を行うことを目的として，提言の施策への反映状況や既往の提言の文章表現や構造を分析した。具体的には，既往の提言の文章の表現や構造を詳細に分析し，提言の各文章を主語，述語，目的語に分類し検討を行った。また提言を社会に発信するまでの手続き(体制)についても，関連する学会を対象に調査した。最終的に，今後，学会が提言を行う際に参考となるポイントについてとりまとめ，地震防災性向上に資する提言のあるべき姿を示した。

Analysis on the Proposals for Earthquake Disaster Reduction by Academic Societies and Their Effects on the Society

Kimiro MEGURO, Yasunori HADA, Hiroyoshi OSHIMA, Masayuki KOHIYAMA, Shinya KONDO, Mitsuaki SAEKI, Gaku SHOJI, Yoshiaki HISADA, and Miho Yoshimura OHARA

土木学会地震工学論文集 (土木学会) 10 2007.08

Research paper (scientific journal), Joint Work, Accepted

本論文は，大都市圏の地震防災性の向上に資する従来よりも効率的で，かつ，より説得力のある提言のあり方を検討することを目的として，土木学会や建築学会が兵庫県南部地震の後に行った提言の分析と提言を取り巻く環境の分析を行った。具体的には，地震被害や地震防災対策の全体像に対する既往の関連学会の提言の位置づけと，対象としてきた課題の分野を明らかにし，これらの提言が社会に及ぼした影響や提言を取り巻く環境の変化を，研究発表，科学技術研究費補助金，国の防災関連予算，及び関連新聞記事等の変化から定量的に分析した。

Experimental Study on Indices to Detect Damage of RC Beam Based on Fourier Analysis of Response to Impact Excitation

Sano, A., Kumagai, Y., and Kohiyama, M.

Asia-Pacific Workshop on Structural Health Monitoring (Keio University) 395-403 2006.12

Research paper (international conference proceedings), Joint Work

Regarding damage detection of reinforced concrete (RC) structure using an impact hammer and a piezoelectric acceleration sensor, experiment and analysis were carried out to propose a reliable index to assess severity of damage to a member of RC structure. A test piece of a RC beam was used. First, the test piece was simply supported and two vertical downward forces were loaded monotonically to damage it. At some stage of damage severity, the test piece was moved out from the loading apparatus, and then was supported by urethane bearings. After that with an impact hammer, an impulse wave was given on the surface of the test piece in which downward forces were applied. The vibration (acceleration) of the normal direction of the surface was measured by the six accelerometers that were placed on the loaded and impact excited surface. Impact excitation was conducted at seven points. The above set of processes of loading (damaging) and measuring response to impact excitation was repeated until the test piece exhibited multiple visible cracks from the bottom to the top of the beam. The accelerograms were analyzed by the Fourier transform and some indices using not only the Fourier amplitude spectrum but also the Fourier phase spectrum were examined on the applicability for detecting damage.

Incentives and Disincentives to Retrofitting: Importance of Risk Communication in Programs of Earthquake Disaster Reduction

Masayuki KOHIYAMA, Miho YOSHIMURA, and Kimiro MEGURO

Journal of Environmental Engineering (Transactions of AIJ) (Architectual Institute of Japan) ( 606 ) 89-96 2006.08

Research paper (scientific journal), Joint Work, Accepted

For programs of earthquake disaster reduction, past studies have revealed that it is quite important not only to provide reliable risk information, but also to promote the communication with others for information exchange. The result of a questionnaire survey to homeowners supported this neighbors’ positive influence to retrofitting and also identified importance to provide engineering information on retrofitting plainly and to improve credibility of contractors of retrofitting work. Hence, interactive risk communication among homeowners, engineers and government officials is desired to assist comprehensive seismic risk management of homeowners. Based on the findings, programs to promote seismic risk management of houses are proposed from a viewpoint of effectiveness of risk communication.

Analysis on Strong Motion Indices Relevant to Damage of Two-Story Wooden Structures Based on Rank Correlation Coefficient

Masayuki KOHIYAMA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 605 ) 55-62 2006.07

Research paper (scientific journal), Single Work, Accepted

Strong motion indices are analyzed on relevance to damage of two-story wooden structures. After nonlinear time history analyses of models with various stiffnesses for nine hundred input motions, a rank correlation coefficient are evaluated with respect to the relevance between intensity of an index and structural damage defined by a certain threshold of maximum story drift. It is clarified that the responses of linear single-degree-of-freedom systems with a particular elongated period and 20% damping ratio show fairly good correlation with the damages. It is observed that specific combinations of stiffnesses tend to disperse the damage, and consequently reduce the relevance.

Urban Damage Detection Using Remote Sensing Technology: Accelerating Response after a Severe Earthquake

KOHIYAMA MASAYUKI

Invited Lecture at National Center for Research on Earthquake Engineering, Taiwan 2006.06

Research paper (other academic), Single Work

Damage Estimation of Urban Houses Considering Seismic Performance and Urban Damage Detection Using Remote Sensing Technology

KOHIYAMA MASAYUKI

Invited Lecture at National Central University, Taiwan 2006.06

Research paper (other academic), Single Work

Correlation between Strong Motion Indices and Damage of Wooden Structures Based on Nonparametric Statistics

Kohiyama, M.

8th National Conference on Earthquake Engineering (100th Anniversary Earthquake Conference) (Earthquake Engineering Research Institute) 8 2006.04

Research paper (international conference proceedings), Single Work, Accepted

To propose more useful strong motion indices and to improve estimation accuracy of building damage, some strong motion indices (peak ground velocity, spectrum intensity, Japan Meteorological Agency seismic intensity, spectral displacement, etc.) are investigated with respect to correlation with damage of wooden structures. A nonparametric correlation coefficient, Spearman’s , is employed as an indicator of accuracy of damage estimation. Multiple input motions are used for nonlinear time history analysis of two-degree-of-freedom models of wooden structures, which have various combinations of story stiffnesses. As a damage model, maximum story drift angle is considered and three levels of threshold, 1/60, 1/30 and 1/15 rad are examined, which approximately correspond to minor, moderate, and major damage of a structure. Distributions of Spearman’s  of the strong motion indices are compared, and it is revealed that displacement response of a linear single-degree-of-freedom system with a damping ratio of 20% and with the elongated period that is determined by a damage threshold, shows fairly good correlation with the structural damage.

Image Fluctuation Model for Damage Detection Using Middle-Resolution Satellite Imagery

Kohiyama, M. and Yamazaki, F.

International Journal of Remote Sensing (Taylor & Francis) 26 ( 24 ) 5603-5627 2005.12

Research paper (scientific journal), Joint Work, Accepted

A damage detection method using middle-resolution satellite images, the Image Fluctuation Model method, is proposed, which employs a stochastic model of the digital number (DN) fluctuation in a normal condition and its significance test. The DN fluctuation model is formulated by considering an imaging process of a satellite sensor and an image registration process. A resulting thematic map is created based on a confidence level (12significance level), which is defined on a pixel-by-pixel basis as follows: the minimum significance level at which the null hypothesis, that the pixel DN can be considered as a sample of the DN fluctuation model, is rejected. The confidence level provides the model-based probability of ground surface change. The method is applied to the 2003 Bam, Iran earthquake using images acquired by Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of Terra. The receiver operating characteristic curves of the method showed better detection performance than temporal image differencing or temporal image ratioing. Though the detection performance of building damage was not comparable to visual inspection on a building basis using high-resolution images of QuickBird, the confidence level map shows similarity at the district level to damage assessment results using high-resolution images.

Damage Detection for 2003 Bam, Iran, Earthquake Using Terra-ASTER Satellite Imagery

Kohiyama, M. and Yamazaki, F.

Earthquake Spectra (Earthquake Engineering Research Institute) 21 ( S1 ) S267-S274 2005.12

Research paper (scientific journal), Joint Work, Accepted

The damaged areas of the 2003 Bam, Iran, earthquake were detected using 15-meter-resolution satellite imagery acquired by Terra-ASTER. First, fluctuation of digital numbers was modeled as a normal random variable based on 17 pre-event images on a pixel-by-pixel basis. Then, the deviation value of each digital number in the post-event image was evaluated and converted into the confidence level, which indicates the possibility of an abnormal ground surface change. The detected damaged areas were verified with a highresolution satellite image and it was observed that the areas with earthquake influence were mostly identified. However, the pixels with significant change were induced not only from heavily damaged buildings but also dusty roads, possibly due to demolition work. It was suggested that prior knowledge like a high-resolution pre-event image would assist the interpretation of the detected result.

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A Study on the Structure of Resident Awareness about Retrofitting of Low Earthquake-Resistant Houses

Miho YOSHIMURA, Kimiro MEGURO, and Masayuki KOHIYAMA

土木学会地震工学論文集 (土木学会) ( 1 ) 10 2005.08

Research paper (scientific journal), Joint Work, Accepted

既存不適格住宅の耐震化の阻害要因は補強技術の問題，居住者の防災意識，家庭事情など多岐にわたる。需要に合致した耐震化推進策が必要である。関東地域の戸建住宅所有者を対象とし，補強工事に関する意識を調査した。家族構成・経済的状況・住宅状態などに応じ，耐震診断・補強関連情報の入手過程を把握した。補強工事の実施意欲に影響を与える要因を明らかにし，住宅所有者による自発的な耐震補強対策の誘導方法について検討した。

Analysis on Strong Motion Indices Relevant to Structural Damage Using Rank Correlation Coefficient

Masayuki KOHIYAMA and Fumio YAMAZAKI

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 594 ) 41-48 2005.08

Research paper (scientific journal), Joint Work, Accepted

This paper discusses the methods to compare the relationship between the strong motion indices and damage of structures. Based on the rank correlation analysis for the dynamic analysis results, it is pointed out that the correlations could change depending on the damage levels and the structural periods. In the nonlinear time history analyses, the responses of wooden structure models of Single-Degree-of-Freedom (SDOF) were simulated for nine hundred input motions. It is observed that the responses of the linear SDOF systems with 20% damping ratio and with elongated periods, considering the damage thresholds, show fairly good correlation with the damages.

Evaluation of Earthquake Disaster Mitigation Programs for Homeowners in Japan Based on Effective Risk Communication

Kohiyama, M., Kiremidjian, A.S., Meguro, K., and Yoshimura, M.

1st International Conference on Urban Disaster Reduction (Earthquake Engineering Research Institute and Institute of Social Safety Science) 8 2005.01

Research paper (international conference proceedings), Joint Work

Seismic risk management programs for homeowners in Japan are reviewed from a viewpoint of effectiveness of risk communication. Past studies have revealed that it is quite important not only to provide reliable risk information, but also to promote the communication with others for information exchange. In addition, a more effective approach would be based on collective behavior rather than expecting individual preparedness activities in Japan. To improve the risk communication and prompt the risk management action, a program of community-level retrofitting activities is proposed that would avoid fear of dishonest contractors, enhance interaction among homeowners exchanging information, and integrate retrofitting work of a single house into revival of urban areas addressing an inner city problem by group demolition and reconstruction.

Damage Detection from High-Resolution Satellite Images for the 2003 Boumerdes, Algeria Earthquake

Yamazaki, F., Kouchi, K., Matsuoka, M., Kohiyama, M., and Muraoka, N.

13th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 13 2004.08

Research paper (international conference proceedings), Joint Work

A strong earthquake of magnitude 6.8 struck the Mediterranean coast of Algeria on May 21, 2003 and the cities of Boumerdes and Zemmouri were most heavily damaged. QuickBird satellite observed these areas before and after the earthquake. Based on these images, the present authors performed visual damage detection of buildings. Using the post-event pan-sharpened image only, totally collapsed buildings, partially collapsed buildings, and buildings surrounded by debris were identified. Some buildings were difficult to judge their damage levels, and thus, the pre-event image was also employed as a reference to judge the damage status. By this visual inspection, a total 3,446 buildings were classified in Boumerdes and 1,399 buildings in Zemmouri based on their damage grades. The locations of refugee tents in the two post-event images were also identified. These observations indicate that high-resolution satellite images can provide quite useful information to emergency management after natural disasters.

Vulnerability Functions for Wooden Houses in Japan Based on Seismic Diagnosis Data

Kohiyama, M. and Yamazaki, F.

13th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 14 2004.08

Research paper (international conference proceedings), Joint Work

The regional difference of seismic capacity of wooden houses in Japan is revealed based on the seismic diagnosis data. The new vulnerability functions of wooden houses, which use the results of seismic diagnosis and an acceleration response spectrum, are proposed. They employ a probability density function of seismic performance indices of wooden houses, which are separated into an index of the resistance force and other indices regarding the degradation of resistance force. The input seismic motion is evaluated based on an acceleration response spectrum and natural periods determined by the indices of resistance force. The application results to the 1995 Hyogo-ken Nanbu earthquake are compared with the damage statistics at the five sites, which have seismic records. Though the proposed vulnerability functions are not based on the damage statistics, the estimated damage ratios coincide fairly well with the actual damage surveyed by local governments.

Early Damaged Area Estimation System Using DMSP-OLS Night-Time Imagery

Kohiyama, M., Hayashi, H., Maki, N., Higashida, M., Kroehl, H. W., Elvidge, C. D., and Hobson, V. R.

International Journal of Remote Sensing (Taylor & Francis) 25 ( 11 ) 2015-2036 2004.06

Research paper (scientific journal), Joint Work, Accepted

The disaster information system, the Early Damaged Area Estimation System (EDES), was developed to estimate damaged areas of natural disaster using the night-time imagery of the Defense Meteorological Satellite Program Operational Linescan System (DMSP-OLS). The system employs two estimation methods to detect the city lights loss or reduction as possible impacted areas; one is the bi-temporal images (BTI) method and the other is the time-series images (TSI) method. Both methods are based on significance tests assuming that brightness of city lights fluctuates as normal random variables, and the BTI method is simplified by introducing the assumption that the standard deviation of city lights fluctuation is constant. The validity of the estimation method is discussed based on the result of the application to the 2001 Western India earthquake disaster. The estimation results identify the damaged areas distant from the epicentre fairly well, especially when using the TSI method. The system is designed to estimate the global urban damage and to provide geographic information through the Internet within 24 h after a severe disaster event. The information is expected to support the disaster response and relief activities of governments and non-governmental organizations.

Damage Detection Method Based on Normal Fluctuation of Digital Numbers in Multi-Temporal Middle-Resolution Images

Kohiyama, M., Estrada, M., and Yamazaki, F.

Monitoring, Prediction and Mitigation of Disasters by Satellite Remote Sensing (MPMD-2004 Symposium) (Disaster Prevention Research Institute, Kyoto University) 123-130 2004.01

Research paper (international conference proceedings), Joint Work

A new damage or change detection method using middle-resolution satellite images is proposed, which employs the probability distribution model of the digital number (DN) fluctuation in a normal condition and its significance test. The DN fluctuation model is formulated by considering imaging process of a satellite sensor and image registration process. The result thematic map is created from the significance level to reject the null hypothesis that the pixel DN can be considered as a sample of the DN fluctuation model. The method overcomes the threshold setting problem in conventional change detection methods.

Law Systems Regarding Seismic Capacity Evaluation of Housing in Japan and Systems Rationalization to Promote House Owners' Action of Seismic Risk Reduction

Masayuki KOHIYAMA, Yuuki ISHIHARA, and Fumio YAMAZAKI

Journal of Social Safety Science (Institute of Social Safety Science) ( 5 ) 113-122 2003.11

Research paper (scientific journal), Joint Work, Accepted

The questionnaire survey on subsidies for seismic diagnosis of private housing was carried out for prefectures and major cities in Japan as of January 2003. The result revealed that 30% of prefectures and 60% of major cities have the subsidies. Though the free-of-charge system gathers more than 100 subsidy users a month, even a small burden charge influences the number of users. The law systems regarding seismic capacity evaluation are reviewed on their purposes and evaluation methods. It is pointed out that the qualified results of seismic diagnosis funded by the subsidies should be used for the discount of earthquake insurance, and the seismic performance should also be certificated for the insurance discount after the retrofit works.

Vulnerability Functions for Wooden Buildings Based on the Data from Seismic Diagnosis –Evaluation of Minor and More Damages Using Acceleration Response Spectrum–

Masayuki KOHIYAMA and Fumio YAMAZAKI

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 570 ) 137-144 2003.08

Research paper (scientific journal), Joint Work, Accepted

The vulnerability function of wooden-frame houses using the results of seismic diagnosis and a response spectrum was proposed. It employs a probability density function of seismic performance indices of wooden houses, which are separated into an index of horizontal resistance force and other indices. The input seismic motion is evaluated based on an acceleration response spectrum and natural periods determined by indices of horizontal resistance force. The application results to the 1995 Hyogo-ken Nanbu earthquake are compared with the damage statistics at the five sites, which have seismic records. Though the proposed vulnerability function is not based on the damage statistics, the estimated ratios for minor and more damages coincide fairly well with the actual damage surveyed by local governments.

Expansion of the Nishinomiya Built Environment Database - Simulation of seismic ground motion distribution and correlation with damage in the 1995 Hyogo-ken Nanbu Earthquake

Kohiyama, M., Yamashita, N., Sato, T., Lu H., Maki, N., Tanaka, S., and Hayashi, H.

Natural Hazards (Springer) 29 ( 3 ) 501-522 2003.07

Research paper (scientific journal), Joint Work, Accepted

The Nishinomiya Built Environment Database, which can be used to analyze the disaster process of the 1995 Hanshin-Awaji Earthquake Disaster in Nishinomiya City, has been expanded with new data entries. The database contains the following very detailed datasets: (1) the urbanization area base map, (2) casualty data, (3) three sets of building damage data surveyed by the Nishinomiya City, the Architectural Institute of Japan and the City Planning Institute of Japan, and the Kobe University, (4) building property data based on the real estate tax roll, (5) photographs of the damaged buildings with the information on the place and orientation of the picture, and (6) the estimated distribution of the seismic ground motion. The seismic ground motion was simulated for the southern part of Nishinomiya City and two verification sites in Kobe City and Amagasaki City. In the simulation, the borehole data of public facilities were used to model the surface soils as one-dimensional layers, taking into consideration the fact that the spatial distribution of the sediment/basement interface forms a slope. The model of the fault rupture process simulated the characteristics of the seismic motion at basement level, and amplification effects of the surface layers were evaluated based on multiple reflection theory. The distribution of peak ground acceleration and peak ground velocity was estimated from acceleration response spectra at each borehole point. In addition, the relationship between simulated seismic ground motion and building damage was studied based on newly proposed band-passed spectrum intensity using the expanded database. This confirmed that detailed categorization is necessary in order to evaluate the fragility functions, especially for reinforced concrete structures. The database should provide fundamental information for identifying the relationship between the ground motions and the extent and pattern of building damage, or the pattern of the occurrence of casualties.

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Process of Housing Damage Assessment: The 1995 Hanshin-Awaji Earthquake Disaster Case

Horie, K., Maki, N., Kohiyama, M., Lu H., Tanaka, S, Hashitera, S., Shigekawa, K., and Hayashi, H.

Natural Hazards (Springer) 29 ( 3 ) 341-370 2003.07

Research paper (scientific journal), Joint Work, Accepted

Rebuilding of victims' livelihoods was a crucial issue in the restoration process in the1995 Hanshin-Awaji Earthquake Disaster. Housing damage assessment influenced most of the rebuilding of the livelihood in the long term, because the Victim Certificates issued by the local governments based on the results of the Housing damage assessment was required to receive most of the individual assistance measures. In the process of Housing damage assessment, many complex problems arose, leading to extensive work on the part of the disaster responders. Consequently, a considerable number of victims were dissatisfied with the assessment and applied for a resurvey. Due to a flood of requests for resurvey, disaster responders had to work on damage assessment, leaving relief activities aside. In order to facilitate Housing damage assessment, this paper discusses the following five points: (1) the processes and the problems of assessments performed in the Hanshin-Awaji Earthquake Disaster, (2) the changes in the nature of information needed by the victims, (3) the improvements over the present damage assessment, (4) the housing situation in Japan, and (5) the international situation on damage assessment. It is obvious from the results that a poor damage assessment system and the size of the disaster produced a very large work load. Differences in appreciation among the investigators also contributed to unfair assessments and led to the victims being increasingly dissatisfied by the survey results. Finally, a design concept for a comprehensive damage assessment system, which has been derived from the above five points, is proposed for post-disaster management.

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Building Damage and Casualties after an Earthquake: Relationship between Building Damage Pattern and Casualty Determined Using Housing Damage Photographs in the 1995 Hanshin-Awaji Earthquake Disaster

Lu H., Kohiyama, M., Horie, K., Maki, N., Hayashi, H., and Tanaka, S.

Natural Hazards (Springer) 29 ( 3 ) 387-403 2003.07

Research paper (scientific journal), Joint Work, Accepted

The relationship between building damage patterns and human casualties in Nishinomiya City - one of the most heavily damaged cities in the 1995 Hanshin-Awaji Earthquake Disaster - was investigated using photographs of damaged buildings. First, the photographs of buildings in which casualties occurred were identified, and the building damage patterns were judged based on the photographs considering the existence of survival space. Then the relationship between the building damage pattern and casualty occurrence, and the characteristics of casualty distribution, were investigated. The main findings were as follows: Most casualties occurred in relatively old two-story wooden buildings in which the ground floor completely collapsed without survival space; casualties occurred at all building damage levels including "no damage", and it can be seen that building damage is the major, but not the sole cause, of casualties in an earthquake; in Nishinomiya City, the regional distributions of casualties due to the collapse of buildings that left no survival space is similar to that of casualties due to other types of building damage.

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Evaluation of Seismic Diagnosis Methods for Wooden Housing Intended for Web Service

Kohiyama, M., Ujita, N., Murao, O., Kato, T., and Yamazaki, F.

7th U.S./Japan Workshop on Urban Earthquake Hazard Reduction 8 2003.03

Research paper (international conference proceedings), Joint Work

Recently, many private and public sectors have provided methods of seismic diagnosis for wooden housing on their Web pages. Since the Internet can easily gather a large number of participants, it is expected that these Web pages will promote house owners to recognize earthquake risks, to carry out the retrofit works, and to join to earthquake insurance. This paper proposes an effective and adequate method for seismic diagnosis of wooden houses through the Internet. First, a questionnaire was carried out to wooden-house owners in Tokyo with the simple diagnosis method that is widely adopted in Japan. Secondly, experts visited and inspected the houses by two methods: the simple method, and an in-depth more accurate method, which calculates eccentricity and story stiffness based on the wall materials and allocations. Finally, three diagnosis results were compared. The results revealed that the owners, who are non-experts, returned the diagnosis results diverging from that of experts while the results of the simple and the accurate methods by the experts matched fairly well. Thus, the simple method itself is effective, but in order to improve non-expert result, the followings are suggested: a) provide a land condition (geologic and geomorphologic) database, b) present sample photographs of foundation cracks to prompt them to check carefully before their diagnosis, c) indicate alternatives of wall length along with a house plan and consider a roof type, d) add the questionnaire entry on types of inner and outer walls, and e) add the questionnaire entries on the second-floor area and the center of gravity.

Understanding the Local Characteristics of Earthquake Risk Awareness of Residents in Sumida and Setagaya

Takaaki KATO, Mitutomo KOMIYA, Hiroaki KAMENO, Takuma SAEKI, Osamu MURAO, Fumio YAMAZAKI, and Masayuki KOHIYAMA

11th Japanese Conference on Earthquake Engineering 3 2423-2428 2002.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

The purpose of this study is to investigate the structure of earthquake risk awareness of residents through analysis on a questionnaire survey in the two districts in Tokyo: Setagaya and Sumida, which are typical residential districts from the viewpoint of urban housing planning. Our study focuses on the relation of the risk awareness of residents and the actual risk of their house, and the preference of the alternative to reduce their risk. In this paper, we clarified the differences dependent on the local characteristics and the universality in these two districts to regard as important, in considering the measure for mitigation planning, earthquake insurance and retrofit of house, and abstracted some points to analyze on in detail in the following study.

Characteristics of Wooden Housing Damage Based on Damage Survey Data of Yonago City in the 2000 Tottori-ken Seibu Earthquak

Takashi KUMITA, Masayuki KOHIYAMA, and Fumio YAMAZAKI

Journal of Social Safety Science (Institute of Social Safety Science) ( 4 ) 135-142 2002.11

Research paper (scientific journal), Joint Work, Accepted

The wooden housing damage due to the 2000 Tottoriken Seibu Earthquake was analyzed using the damage survey data investigated by Yonago City. It was clarified that the actual housing damage ratios are lower than estimated results based on simulated peak ground velocity and fragility curves that were derived from the data of the 1995 Hyogo-ken Nanbu Earthquake. Damage mode, which is combination of roof, wall, and structure damage ratios and tilting levels, were calculated for each topographically classified area, and its regional trend was revealed.

Analysis on Regional Characteristics of Seismic Performance Indices of Wood-Frame Buildings Based on the Results of Seismic Capacity Evaluation in Yokohama and Himeji

Yuuki ISHIHARA, Masayuki KOHIYAMA, and Fumio YAMAZAKI

11th Japanese Conference on Earthquake Engineering 2 2091-2096 2002.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

In the present methods to estimate buildings’ damage due to an earthquake, empirical fragility curves based on damage statistics are mostly employed. The structural type and construction period were considered in developing them, but regional characteristics were not considered well. The objective of this study is to analyze the results of seismic capacity evaluation conducted in two cities, Yokohama and Himeji, for more accurate damage estimation. From the analysis of the data, it is observed that there are significant differences in the seismic performance of the buildings in the two cities even though they have the similar structural type and construction period.

Analysis on Regional Characteristics of Seismic Performance Indices of Wood-Frame Buildings in Japan Based on the Results of Seismic Capacity Evaluation

Masayuki KOHIYAMA and Fumio YAMAZAKI

11th Japanese Conference on Earthquake Engineering 2 2097-2102 2002.11

Research paper (conference, symposium, etc.), Joint Work, Accepted

The regionality of seismic performance indices is analyzed based on the results of seismic capacity evaluation employed to buildings of all over Japan. The evaluation results are aggregated into eight regions: Tohoku, Kanto, Hokushinetsu, Chubu, Kansai, Sanyo, Shikoku, and Kyushu, considering culture and climate. The distributions of the construction year and total area of floor space are examined of their similarity to those of Housing and Land Survey taken by the Statistics Bureau of Japan. Buildings in Tohoku show the lowest performance indices in eccentricity, but the highest in horizontal resistance. The ratio of buildings with construction year older than 1981 and area less than 50 m2 should be adjusted to that of the survey result because they have poor performance indices.

Seismic Observation System for a Building and Surrounding Ground in Komaba Research Campus of the University of Tokyo

Calle, G. D., Kohiyama, M., and Yamazaki, F.

7th U.S. National Conference on Earthquake Engineering 10 2002.07

Research paper (international conference proceedings), Joint Work

Recently, the Institute of Industrial Science of the University of Tokyo has been moved from Roppongi Campus to Komaba Research Campus. In the relocation, seismic observation system was newly set up in the institute's building, on the ground surface, and in a borehole. The observation system has collected the records from six seismic events. On the basis of these records, site and building responses were analyzed. The results showed general characteristics of the seismic response in the urban center of Tokyo, particularly, the site amplification due to sediments over Tokyo Formation. A particular soil anisotropy was found around 4.2 Hz due to the soil-structure interaction. In the future, more observation records will be collected and it is expected that the data may provide the details of the site and building response characteristics.

Detection of Damage Due to the 2001 El Salvador Earthquake Using Landsat Images

Estrada, M., Kohiyama, M., Matsuoka, M., and Yamazaki, F.

22nd Asian Conference on Remote Sensing 2 1372-1377 2001.11

Research paper (international conference proceedings), Joint Work

A strong earthquake hit El Salvador on January 13, 2001. The earthquake with a magnitude of 7.6 caused huge damage in the urbanized areas as well as numerous landslides. In case of large scale earthquakes, the identification of hard hit areas is important and necessary information for decision-makers to handle the disaster relief process. In this study, remote sensing images taken before and after the earthquake by Landsat 7 (ETM+) satellite are compared to identify the location of landslides and hard hit urban areas. The proposed method uses the rationing between bands in the visible range as well as the sharpening of the multi-spectral bands by merging with the panchromatic band. It is expected that with the help of this additional band the identification of landslides and damaged areas will be improved.

Time-Series Images Method for the Improvement of Estimation Accuracy of Early Damaged Area Estimation System (EDES) Using DMSP/OLS Nighttime Imagery

Masayuki KOHIYAMA, Haruo HAYASHI, Norio MAKI, Mitsuhiro HIGASHIDA, Herbert W. KROEHL, Christopher D. ELVIDGE and V. Ruth HOBSON

Journal of Social Safety Science (Institute of Social Safety Science) ( 3 ) 173-180 2001.11

Research paper (scientific journal), Joint Work, Accepted

The new method is proposed to estimate damaged areas using the Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS) nighttime imagery for the Early Damaged Area Estimation System (EDES). The former method uses two-acquisition-date images of pre- and post-events, but it has problems of weakness for cloud influence, misdetection of damaged areas due to water reflection of city lights, and tendency to neglect damages in small towns. To address these problems, the proposed method employs significant tests on a pixel basis based on each pixel's average and standard deviation, which are evaluated from time-series images during gain stable periods around new moon phases.

Resolution Improvement of Frequently Observed Satellite Imagery for Urban Characterization

Kohiyama, M. and Yamazaki, F.

22nd Asian Conference on Remote Sensing 1 158-163 2001.11

Research paper (international conference proceedings), Joint Work

This paper proposes the method to develop a high-resolution image of urban properties from frequently observed low-resolution images based on the statistic process assuming urban properties have little temporal change. Because disaster responders sometimes have difficulty to obtain the map data in a digital form especially in developing countries, it is well known that satellite imagery and aerial photographs can support disaster response and rescue activities. But high-resolution images that can provide roads and buildings information expense considerably high when acquiring wide range data by means of aerial photographs or imagery of recently launched satellites with high-resolution sensors. On the other hand, satellite images of spatial resolution of 10 to 100 meter order cost comparatively low. The paper discusses the number of low-resolution images to develop a high-resolution image. First, a one-meter-resolution image derived from an aerial photograph is used as a truth image. Three-meter-resolution image is also evaluated as a reference high-resolution image. Secondly, a nine-meter-resolution image, which simulates an image scanned by a low-resolution sensor of satellites, is evaluated with a randomly selected offset of scan line. The same cell size as a reference image, i.e. three meter is employed for the low-resolution images. Thirdly, a resolution-improved image is synthesized from the average and standard deviation based on each pixel calculation of the simulated images. Then the difference between the reference image and synthesized image is evaluated. Finally, the relationship between the number of low-resolution images and the standard deviation of differences of all pixels in the average image is analyzed. The result quantitatively clarifies that a high-resolution image of urban properties with little temporal change can be developed with a sufficient number of low-resolution images when the precise geolocation is guaranteed.

Automatic Detection of Building Properties from Aerial Photographs Using Color and 3D Configuration

Kokubu, K., Kohiyama, M., Umemura, K., and Yamazaki, F.

22nd Asian Conference on Remote Sensing 2 1197-1202 2001.11

Research paper (international conference proceedings), Joint Work

The buildings properties in spatial databases are very useful for urban planning, disaster mitigation, insurance business etc. But the databases in some governments are not freely available since they include private information. Therefore, the data acquisition mostly depends on image interpretation of photographs and field surveys. Consequently it is time-and labor-consuming and very costly to construct databases, and it is not easy to maintain the data up-to-date and to employ them in wide use. In this study, automatic detection method of building properties based on aerial photographs is proposed and the result is verified by the database made in a conventional way of data acquisition. The method consists of the following steps: (1) geometric correction and gray scale conversion of aerial photographs, (2) stereo matching and evaluation of building heights, (3) evaluation of building areas, (4) color and texture analysis, and (5) classification of buildings. Buildings are classified into the following categories: (a) detached houses, apartment buildings and multi-storied buildings. (b) wooden and non-wooden buildings. The method is applied for a target area in Tokyo and the result is compared with the ground truth data investigated by the authors and the database provided by of Tokyo Metropolitan Government. As a result, it is found that low-storied apartment buildings and multi-storied buildings are correctly identified and they can be classified into proper structural types.

Framework for Damage Assessment Training System

Horie, K., Maki, N., Hayashi, H., Kohiyama, M., Shigekawa, K., and Tanaka, S.

8th International Conference on Structural Safety and Reliability (International Association for Structural Safety and Reliability) 8 2001.06

Research paper (international conference proceedings), Joint Work, Accepted

Damage Assessment Training System (DATS), which consists of an effective damage assessment system and a training system for its use, is proposed to enhance awareness and skills of disaster responders. DATS is designed based on the analysis of building damage assessment performed following the 1995 Hanshin-Awaji Earthquake Disaster. It integrates several improvements over the building damage assessment methods currently in place, and should provide information on housing damages in a much more timely fashion. It is aimed at expediting the work involved in disaster response, therefore, disaster responders would be relieved from the extensive work of damage assessment and should be able to devote themselves to higher-quality service for livelihood rebuilding of victims.

Validity Study of EDES Application to Taiwan Chi-Chi Earthquake Disaster

Kohiyama, M., Hayashi, H., Maki, N., and Hashitera, S.

21st Asian Conference on Remote Sensing 1 407-412 2000.12

Research paper (international conference proceedings), Joint Work

The authors are developing the Early Damaged Area Estimation System (EDES), which provides the information as to the estimated impacted areas after any significant earthquake based on nighttime lights observed by the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). The estimation method is based on the detection of significant reductions or loss of lights in nighttime images following the event, for it can be expected that city lights will observably decrease after a large earthquake. In the 1999 Taiwan Chi-Chi Earthquake Disaster, there was a countrywide power cut due to the damage of the transmission facilities in Chungliao and Tienlun. The post-event image seems to reflect this influence in appearance compared with a pre-event image, but the further investigation is needed because the gain setting of OLS changes along with lunar phase and elevation, and visible-near infrared (VNIR) band imagery only provides relative light intensity. This paper presents a new method to estimate damaged areas based on a radiance-calibrated image and a method to estimate gain and radiance of observed VNIR imagery, and the validity of the estimation result of EDES application to the Chi-Chi Earthquake is discussed using the electric load data before and after the earthquake.

Development of Early Damaged Area Estimation System (EDES) Using DMSP/OLS Nighttime Imagery

Masayuki KOHIYAMA, Haruo HAYASHI, Norio MAKI, Shin HASHITERA, Masashi MATSUOKA, Herbert W. KROEHL, Christopher D. ELVIDGE and V. Ruth HOBSON

Journal of Social Safety Science (Institute of Social Safety Science) ( 2 ) 79-86 2000.11

Research paper (scientific journal), Joint Work, Accepted

The Early Damaged Area Estimation System (EDES) is proposed to support emergency response in a disaster. EDES provides the geographic information of possible impacted areas within 24 hours after an earthquake on the Internet The estimation method is based on the detection of significant reductions or loss of lights in nighttime imagery observed by the Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS). Noise in suburban areas and cloud influence in a pre-event image are addressed by using a cloud-free stable lights image derived from a time series of OLS observations. Appropriate geographic information is discussed to support relief activities and to contribute a reduction in the digital divide problem in global disaster management activities.

International Collaboration for the Early Damaged Area Estimation System Using DMSP/OLS Nighttime Images

Hayashi, H., Hashitera, S., Kohiyama, M., Matsuoka, M., Maki, N., Fujita, H., and Elvidge, C. D.

IEEE 2000 International Geoscience and Remote Sensing Symposium 6 2697-2699 2000.07

Research paper (international conference proceedings), Joint Work

In the Hanshin-Awaji earthquake disaster, the lack of information about where the earthquake damaged areas were prevented early and effective emergency responses and relief. Since then, the national and some local governments in Japan have developed GIS-based damage estimation systems, but few other countries have such systems as yet. Nighttime city lights decreased significantly after a large earthquake, and the DMSP/OLS imagery is suitable for the early estimation of the damaged areas. The damaged areas of the 1999 Kocaeli earthquake in Turkey and 1999 Ji-Ji earthquake in Taiwan were estimated by using DMSP, and the results showed a good match with the real reported damage. We propose a new program through international collaboration to support emergency response and relief activities by providing information as to the estimated impacted areas within the first 24 hours after any significant earthquake. This program consists of the following steps: (1) acquire the earthquake hypocenter data through the Internet, which is for example announced by the USGS. (2) Determine the sampled area of the images by the attenuation formula of earthquake ground motion. (3) Obtain corresponding both time-wise and area-wise DMSP/OLS nighttime images from NOAA/NGDC. (4) Estimate the damaged areas by analyzing the statistically significant decrease in the light intensity of the images. (5) Create a thematic map to present the estimation results as geographic information. (6) Disseminate the resulting map widely and quickly through the WWW.

Earthquake Damaged Area Estimation Using DMSP/OLS Night-time Imagery: Application for Hanshin-Awaji Earthquake

Takashima, M., Hayashi, H., Kimura, H., Kohiyama, M., Kroehl, H. W., Elvidge, C. D., and Hobson, V. R.

IEEE 2000 International Geoscience and Remote Sensing Symposium 1 336-338 2000.07

Research paper (international conference proceedings), Joint Work

After the Marmara earthquake disaster in Turkey (Aug.1999), Kohiyama et al. proposed a method to estimate the impacted area of the earthquake using visible and near-infrared (VNIR) satellite imagery provided by the Defense Meteorological Satellite Program's Operational Linescan System (DMSP/OLS), and succeeded in estimating the impacted area of the Marmara earthquake disaster and the Ji-ji earthquake disaster in Taiwan (Sep. 1999) based on their method. They assumed that the brightness of the area would decrease if the buildings collapsed or blackout occurred due to the earthquake. Then, those areas whose brightness decreased significantly after the earthquake compared with before the earthquake were estimated as the impacted area. The purpose of the present study is to check the validity of the above mentioned method by the application for the Hanshin-Awaji Earthquake (05:46 Jan. 17, 1995) in which the more detailed and various types of damage data due to the earthquake are available as compared with the verification in Turkey.

Proposal for the Effective Building Damage Assessment for Disaster Management

Masayuki KOHIYAMA, Kei HORIE, Norio MAKI, Haruo HAYASHI and Satoshi TANAKA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 531 ) 189-196 2000.05

Research paper (scientific journal), Joint Work, Accepted

Effective damage assessment in terms of disaster management is proposed, which consists of both visual survey based on damage patterns of buildings for prompt service and resurvey for citizen's assent to the assessed damage. Problems which Nishinomiya City encountered in issuing certification of building damage reveals an extent of visual survey and necessity of resurvey in issuing process. Difference between two visual surveys of buildings damaged by the Hanshin-Awaji Earthquake Disaster in Tsukiji District, Amagasaki City shows difficulty in finding differential settlement caused by liquefaction and integrated damage patterns of buildings are proposed for effective field investigation.

Development of Building Damage Chart for Post Disaster Management

Horie, K., Maki, N., Kohiyama, M., Lu H., Tanaka, S., Hashitera, S., and Hayashi, H.

12th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 8 2000.01

Research paper (international conference proceedings), Joint Work

It is found from the questionnaire about the victim’s need for information regarding livability and house repair that the victims needs the information about housing options at the first one week after the Great Hanshin-Awaji Earthquake. However, Building Safety Evaluation, which was the first damage assessment for the individual houses, conducted 6 days after the earthquake from January 23rd to February 9th, 1995. The information needs of the victims cannot be sufficiently fulfilled. The building damage assessment must be conducted both quickly and exactly. It is conceivable that building damage survey using the damage chart is effective. This paper evaluates the effectiveness of the damage chart for damage assessment, and classifies photographic data that are linked to the geographic information systems (GIS) database of Nishinomiya City, based on the damage chart. In addition, we develop the damage chart of wooden structures affected by liquefaction from the case of Amagasaki City.

Human Casualty Estimation Due to Urban Earthquake

Lu H., Kohiyama, M., Maki, N., Tanaka, S., and Hayashi, H.

12th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 8 2000.01

Research paper (international conference proceedings), Joint Work

Since the 1995 Hanshin-Awaji earthquake disaster, damage estimation analyses for potential earthquake hazards have been carried out by many administrative organizations in Japan. One of the key issues in these analyses is to estimate the number and spatial distribution of human casualties as accurately as possible. We focused on Nishinomiya City, which was one of the most heavily damaged cities in the Hanshin-Awaji earthquake disaster, and constructed a built environment database of Nishinomiya City. Using this database, constructions of the age and sex of individuals and the spatial distribution of the dead, as well as the relationships between the ages of houses and ages of the dead were investigated. This paper provides a technique of constructing a relational geographic information system (GIS) database with several different types of data. Using this GIS database and through Weibull analysis, we arrived at two conclusions regarding the distribution of the age and sex of the dead caused by the earthquake. (1) The earthquake mortality rate distribution of the under-50-year-old age group exhibits a constant occurrence pattern, and that of the over-50-year-old age group exhibits an increasing occurrence pattern. (2) The high ratio of the aged living in relatively old houses is one of the reasons resulting in the higher mortality rate of the aged than that of the young.

A Study on Damaged Building Data of the 1995 Hyogo-ken Nanbu Earthquake

Kohiyama, M., Mizukoshi, K., Ishida, H., Torisawa, K., and Tsugawa, T.

12th World Conference on Earthquake Engineering (International Association for Earthquake Engineering) 8 2000.01

Research paper (international conference proceedings), Joint Work

Fragility functions of buildings, which show the relation between seismic intensity and building damage ratio, are used for estimation of building damage caused by an earthquake. Fragility functions are formulated statistically by data of seismic intensity and building damage ratio on cell units and area size of the cells should be considered to calculate damage ratios. In this paper, the characteristics of damage ratio data are discussed using GIS (geographic information system) data of buildings damaged by the 1995 Hyogo-ken Nanbu Earthquake. First, the two databases of the different parties, which concerns buildings damaged by the earthquake, were compared in terms of the method of each survey and their criteria of damage ranking. It was found that the criteria of damage ranking of the two databases do not differ much, but numbers of damaged buildings and the damage ratios in each rank differ remarkably from each other. Secondly, based on the damage ratios in terms of various cell sizes, it is pointed out that the adequate cell size ranges from 10,000 m2 to 200,000 m2 from the viewpoints of the number of target buildings in the unit and the resolution of the damage distribution.

Use of DMSP-OLS Images for Early Identification of Impacted Areas Due to the 1999 Marmara Earthquake Disaster

Hashitera, S., Kohiyama, M., Maki, N., Hayashi, H., Matsuoka, M., and Fujita, H.

20th Asian Conference on Remote Sensing 2 1291-1296 1999.11

Research paper (international conference proceedings), Joint Work

The effective international disaster response and relief in a large-scale disaster such as the earthquakes in Turkey and Taiwan become possible by the effective distribution of limited resources, both human and physical. Therefore, identifying the spatial distribution of damaged areas is essential on first step.
A method for the early identification of earthquake damaged areas is proposed based on night-light data obtained by the US DMSP (Defense Meteorological Satellite Program)-OLS (Operational Linescan System). The significance in the data of night-light intensity between before and after the reduction in Marmara earthquake disaster in Turkey on August 17, 1999 can be used to estimate possible impacted areas.

A Study on the Occurrence Mechanism of Human Casualty in Nishinomiya City due to the 1995 Great Hanshin-Awaji Earthquake

Hengjian LU, Masayuki KOHIYAMA, Norio MAKI, Haruo HAYASHI, Satoshi TANAKA and Akiyoshi NISHIMURA

Journal of Social Safety Science (Institute of Social Safety Science) ( 1 ) 151-156 1999.11

Research paper (scientific journal), Joint Work, Accepted

In order to reduce human casualties and to set up a correct estimation of death caused by earthquake, it is important to make clear the related factors effecting human casualty. This study focused on Nishinomiya City, which was one of the most heavily damaged city in the 1995 Hanshin-Awaji Earthquake Disaster and a construction of age and sex of the dead is investigated. The investigations prompted two conclusions: (1) The distribution of the earthquake mortality rate of the under-50-year-old age group exhibits a constant occurrence pattern of Weibull distribution, and that of the over-50-year-old age group exhibits an increasing occurrence pattern. (2) The high ratio of the aged living in relatively old houses is one of the reasons resulting in the higher mortality rate of the aged than that of the young.

Study on Cell Size for Building Damage Ratio Based on Data of the 1995 Hyogo-ken Nanbu Earthquake

Masayuki KOHIYAMA, Kaoru MIZUKOSHI, Hiroshi ISHIDA, and Kazuaki TORISAWA

Journal of Structural and Construction Engineering (Transactions of AIJ) (Architectural Institute of Japan) ( 522 ) 137-142 1999.08

Research paper (scientific journal), Joint Work, Accepted

Characteristics of damage ratio data were discussed using GIS data of buildings damaged by the 1995 Hyogo-ken Nanbu Earthquake. A regression analysis of the damage ratio for two kinds of area unit showed that damage ratios reported by Kobe University were about 60% of those reported by Building Research Institute. An analysis of damage ratios according to different cell areas revealed that the adequate cell size for data collection ranges from 10,000 to 200,000 m^2 from the viewpoints of the number of target buildings in the unit and the resolution level for the damage distribution.

Development of GIS-Aided Loss Estimation System for Earthquake Hazard

Masayuki KOHIYAMA, Kaoru MIZUKOSHI, Hiroshi ISHIDA, Shigeru NAGATA, Hiroyuki KANEKO, Masaru MATSUMOTO, Harumi YASHIRO, and Yoshiaki OGANE

AIJ Journal of Technology and Design (Architectural Institute of Japan) ( 7 ) 187-191 1999.02

Research paper (scientific journal), Joint Work, Accepted

A loss estimation system for earthquake hazard capable of evaluating all of Japan was developed. A GIS (Geographic Information System) for personal computers is utilized for this system, which assists in interactive selection of the assumed earthquake and representation of the estimated results on a computer screen. Source parameters of the assumed earthquake can be derived from a database of active faults and historical earthquakes. Earthquake ground motion, liquefaction and earthquake-triggered fire are considered in order to estimate building damage ratios. An insurance company's exposure can quickly be estimated by linking this system to an insurance contract database.

Shape Optimization of a Double-Layer Space Truss Described by a Parametric Surface

Ohsaki, M., Nakamura, T., and Kohiyama, M.,

International Journal of Space Structures 12 ( 2 ) 109-119 1997.04

Research paper (scientific journal), Joint Work, Accepted

A method is presented for finding the optimal configuration of a double-layer space truss described by a parametric surface. The number of design variables is drastically reduced, without sacrificing the smoothness of the upper layer surface, by using the control net parameters as design variables. The coordinates of the lower nodes are defined by using a vertical or normal offset vectors from the upper surface. Curvatures of the curve associated with the lower polygon are calculated for evaluating feasibility and regularity of the a double-layer lattice space truss. In the examples, a feasible optimum design, which minimizes compliance under constraints on structural volume, are successfully found by using the proposed method. It is shown that the optimal solutions strongly depend on the specified ratios of the cross-sectional areas of the members.

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