Details of a Researcher - Kohiyama, Masayuki

Papers - Kohiyama, Masayuki

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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.

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