Haruyuki Kitamura

Performance of Seismic Protection Technologies during the 2011 Tohoku-Oki Earthquake

Many buildings in the Tohoku and Kanto area were strongly shaken during the Tohoku-oki earthquake on 11 March 2011. Soon after the earthquake, the Japan Society of Seismic Isolation (JSSI) established committees to investigate the performance of structures where modern seismic protection methods were used. Since response-control technologies are relatively new, few systems had been validated with actual earthquakes. Generally, the various buildings performed well, and there were no failures of superstructures of base-isolated or supplementally damped buildings. Failures of numerous expansion joints and lead dampers in base-isolated buildings are described. Acceleration records of both base-isolated and supplementally damped buildings are analyzed and their seismic performance characteristics are discussed.

Seismic Performance of Seismic-isolated Building for Long-period Ground Motion and Limited Performance of Seismic Isolator

earthquakes. The Special Investigation Committee on Response to Catastrophic Disasters Including the Anticipated Tokai Earthquake (chair: Hiroshi Akiyama) of the Architectural Institute of Japan (AIJ) has been carrying out research to prepare for the occurrence of these earthquakes. The committees report clarified the need to study the cumulative energy absorbing capacity and other performance parameters of seismic isolators, as well as the maximum value of seismic isolation layer displacement and other responses by seismic-isolated buildings under long-period earthquake motions. Further, the report demanded further verification of the critical performance of these buildings under larger earthquake motions than assumed in the design phase. 1),2) By Revision of the Building Standard Law in 2000, use of isolators and dampers approved by the Minister has been stipulated in the design procedure of isolation buildings. As verifications of various characteristics by testing full-scale specimens are required to obtain the approval, the manufacturers carried out a lot of experiments, which have made characteristics of various isolation devices clearer 3),4),5),6) .

STUDY ON DYNAMIC CHARACTERISTICS OF PILE TOP SEISMIC ISOLATION BUILDINGS BY EARTHQUAKE RESPONSE ANALYSIS: Evaluation of characteristics of laminated rubber bearing considering seismic behaviors@@@動的挙動を考慮した積層ゴムの力学特性の評価

This paper describes the seismic behaviors of laminated rubber bearing in pile top seismic isolation buildings through numerical experiments considering the nonlinearity of the laminated rubber bearing and the dynamic soil–structure interaction. It also describes the problems of current structural design method. The horizontal stiffness and movement of the inflection point of the laminated rubber bearing in a pile top seismic isolation building are studied through a parametric analytical study. A quantitative evaluation of the dynamic characteristics of the laminated rubber bearing is conducted, and it is found that the dynamic characteristics of the laminated rubber bearing can be predicted using simple indicators.

THE VIBRATION CONTROL PERFORMANCE EVALUATION METHOD BASED ON ABSORBED ENERGY FOR ELASTIC FRAME HAVING HYSTERETIC DAMPERS

To estimate the seismic performance in the difference of the arrangement situation of the hysteretic dampers which have a lot of influence for the vibration control effects, it is necessary to carry out many time-history analyses. However, it is difficult to comprehensively understand the relationship between the damper arrangement and vibration control effect from only the time-history analysis results. This paper proposes the vibration control performance evaluation method based on the absorbed energy without using the time-history analyses. This method can estimate of the best configuration pattern of dampers, and it is very effective for seismic control design.

A STUDY ON TORSIONAL BEHAVIORS OF HIGH-DAMPING RUBBER BEARINGS WITH HYSTERETIC AND VISCOUS DAMPING MECHANISM BY TIME-HISTORY ANALYSIS UNDER BI-AXIAL SEISMIC WAVES

In this study, torsional behaviors of high-damping rubber bearings under various bi-axial seismic waves observed in the site are investigated by time-history analysis with single mass system. A simplified numerical model for the shear properties of the bearings composed of a hysteretic damping element and a viscous damping element is proposed for the analysis. The influences of the characteristic of the seismic wave to the torsional strain generated in the bearings by the effect of damping elements are evaluated. Furthermore, relations between the behavior of the bearings during seismic response and the oval-loading test which is specified for the test of bi-axial ultimate characteristics are examined.

DAMAGE EVALUATION OF SEISMIC ISOLATED DAMPER BY RESPONSE ANALYSIS USING OBSERVED SEISMIC RECORDS OF THE 2011 OFF THE PACIFIC COAST OF TOHOKU EARTHQUAKE

The 2011 off the Pacific coast of Tohoku earthquake generated the main shock with long-duration and long-period and the magnitude 7.0 class aftershocks many times in a wide range of eastern Japan. The horizontal displacement response of the isolated building caused by them was about 0.4 m. They damaged seismic isolated dampers such as steel dampers and lead dampers. This paper presents to evaluate responses of isolated buildings and the damage of seismic isolated dampers by results of response analysis using simple isolated building model under bi-axial horizontal loading in main shock and aftershocks observed at 6 points from Aomori to Tokyo.

ENERGY BALANCE-BASED SEISMIC RESPONSE PREDICTION METHOD FOR STEEL STRUCTURE CONSIDERING EFFECTIVE HYSTERETIC DAMPER DEFORMATION

The structural-seismic safety is evaluated by the amount of plasticity energy. The prediction method based on energy balance has been established, and this method is founded on simplified shear spring model. In case of the vibration control structure having the hysteretic dampers, the shear spring model excessively evaluates the efficiency of the vibration control of the dampers because the effective damper deformation is not considered. In this paper, the shear spring model considering the effective deformation of the hysteretic damper is made by connecting the series spring to the damper. This series spring can be obtained without the push-over analysis of the material model. In addition, the prediction method based on energy balance considering the effective damper deformation is proposed.