研究者詳細 - 小檜山　雅之

論文 - 小檜山　雅之

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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年02月

研究論文（学術雑誌）, 共著

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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深層ニューラルネットワークを用いた損傷判別におけるk近傍法とウェルチのt検定に基づく未学習損傷パターンデータの検知

小檜山雅之，普天間基，岡一也，山下拓三

JCOSSAR2019論文集（公益社団法人日本材料学会） 319 - 326 2019年10月

研究論文（その他学術会議資料等）, 共著, 査読有り

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年09月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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年09月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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年07月

研究論文（学術雑誌）, 共著, 査読有り, 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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層間変形を低減する層間同調質量ダンパーの設計法とその検証実験

小檜山雅之，大村真史

構造工学論文集（日本建築学会） 65B 77 - 84 2019年03月

研究論文（学術雑誌）, 共著, 査読有り, 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

Kohiyama M., Yokoyama H.

Frontiers in Built Environment （Frontiers in Built Environment） 4 （ 38 ） 1 - 12 2018年07月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 2297-3362

© 2018 Kohiyama and Yokoyama. 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年07月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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

Ho C., Zhu Y., Lang Z., Billings S., Kohiyama M., Wakayama S.

Journal of Sound and Vibration （Journal of Sound and Vibration） 424 302 - 317 2018年06月

研究論文（学術雑誌）, 共著, 査読有り, ISSN 0022460X

© 2018 Elsevier Ltd 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 3 min. 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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地区耐震化の検討を目的とした消火・延焼・避難の観点での街路網の評価

河西洋亮，小檜山雅之

日本地震工学会論文集（日本地震工学会） 18 （ 2 ） 35 - 50 2018年05月

研究論文（学術雑誌）, 共著, 査読有り

建物倒壊による道路閉塞は，地域住民の避難，消防機関による消火・救援活動等を阻害し，延焼による被害を拡大する要因ともなる．本論では消火確率・非延焼棟数比・避難達成率の3つの指標で，地域の防災力を評価する方法を提案する．指標の評価においては建物倒壊率，出火確率などをもとにモンテカルロ法を用いて行う．格子状道路と放射環状道路の2つの仮想地区に対し提案指標を評価した結果，提案指標が街路網の特徴を反映し地域の防災力を表現できることと地域の特徴を考慮して耐震補強計画の優先度を比較分析できることを確認した．

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強震動を受ける木造住宅の質量偏在と平面形状に起因した捩れ振動の動的解析による評価

岡一也，小檜山雅之

構造工学論文集（日本建築学会） 64B 479 - 492 2018年03月

研究論文（学術雑誌）, 共著, 査読有り, 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年08月

研究論文（研究会，シンポジウム資料等）, 単著, 査読有り

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年08月

研究論文（学術雑誌）, 共著, 査読有り

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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地震と雪の荷重組合せを考慮した動的解析に基づく鋼構造大スパン建物の被害確率評価

山﨑賢二，小檜山雅之

構造工学論文集（日本建築学会） 63B 83 - 89 2017年03月

研究論文（学術雑誌）, 共著, 査読有り

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年01月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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年01月

研究論文（国際会議プロシーディングス）, 共著, 査読有り

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年07月

研究論文（国際会議プロシーディングス）, 共著

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年07月

研究論文（国際会議プロシーディングス）, 共著

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年07月

研究論文（国際会議プロシーディングス）, 共著

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.

セミアクティブ免震建物の被害確率を低減するスライディングモード制御の制御パラメータ設計

若山志津佳，小檜山雅之

日本地震工学会論文集（日本地震工学会） 16 （ 3 ） 75 - 93 2016年03月

研究論文（学術雑誌）, 共著, 査読有り

スライディングモード制御はパラメータ変動やモデルの不確かさに対して優れたロバスト性を持つ。しかし、複数の制御パラメータを要し、それらの設計法は確立されていない。本論文では、これらの制御パラメータを建物の供用期間における被害発生確率を最小化するよう決定する設計手順を提案する。セミアクティブ免震建物を対象に検討を行い、提案手法に基づきパラメータを決定した場合の被害確率と、従来の手順による一定の強さの設計用地震動に対する応答を最小化するようパラメータを決めた場合の被害確率を比較し、その差を明らかにする。

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小檜山　雅之

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