Published papers

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。

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。

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。

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.

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.

11層大学校舎と26層超高層建物にセミアクティブ免震システムを導入した事例について，2011年東北地方太平洋沖地震の疑似3次元解析によるシミュレーション結果と地震観測記録を比較し，性能を検証した。地震時の動作信頼性，ならびに免震層の変形抑制と加速度応答の低減について，良好な性能を有していることを確認した。

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.

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.

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.

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.

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.

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.

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.

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.

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。

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.

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.

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.

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.

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.