Torsional strain is calculated by horizontal bi-directional loading tests, which is known to analyze the images of the dots painted on the surface of high-damping rubber bearings, because it can't be measured directly. In elliptical orbit loading tests, residual torsional strain, which increases the torsional strain, is confirmed. A method for evaluating torsional strain based on torsional stress is proposed, which consider an influence of residual torsional strain. Seismic response analyses are performed to evaluate the dynamic behavior of an isolated building under horizontal bi-directional earthquake excitations.

The purpose of this paper is to clarify the hysteretic behaviors of seismic isolation bearings under horizontal bi-directional deformation. The force vector of seismic isolation bearings with damping consists of elastic component and damping component. Elastic component and damping component are caused in a different direction by horizontal bi-directional deformation. We apply an analytical model for seismic isolation bearings which expresses the constantly changing direction of the two force components to lead rubber bearing. The validity of the model is confirmed by comparing analytical results calculated by the model with experimental results of horizontal bi-directional loading tests of lead rubber bearing. Based on the analytical results calculated by the model, investigation of hysteretic absorbed energy of lead rubber bearings under horizontal bi-directional deformation is conducted.

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It has been reported the vibration generated by the vertical motion of a large number of audiences in a live hall during a live performance brings unpleasant vibration to surrounding buildings. As a countermeasure against this vibration problem, we have developed a vibrationproof floor system using inertial mass device and introduced the system to an actual live hall. Excitation tests in principle model and the actual hall were conducted to demonstrate the effect of the system. As a result of the tests and simulation analysis, it is proved the proposed system is very effective on the vibration problem.