SUMMARYThis paper presents a study for the development of a system capable of performing real-time pseudo dynamic testing. The system combines the basics of the pseudo dynamic test with a dynamic actuator, a digital displacement transducer and a digital servomechanism. The digital servo-mechanism has been introduced to ensure accurate displacement and velocity control, in which digital feedback control with a time interval of 2 msec has been performed continuously during actuator motion. Using the system, pseudo dynamic tests under sinusoidal and earthquake ground motion are carried out for a structure having a viscous damper, demonstrating that a perfectly real-time pseudo dynamic test can be achieved by incorporating the modified central difference method into an extra buffer operation of the digital servo-mechanism. The responses solved by the pseudo dynamic tests are compared with the responses of the test structure as well as those obtained from post-numerical analysis, and it is found that the real-time pseudo dynamic test conducted in this study is accurate.

SUMMARYThis paper describes the results of shaking table tests to ascertain the ultimate behavior of slender baseisolated buildings and proposes a time history response analysis method, which can predict the ultimate behavior of base-isolated buildings caused by buckling fracture in laminated rubber bearings. In the tests, a base-isolated structure model weighing 192 kN supported by four lead rubber bearings is used. The experimental parameters are the aspect ratio of height-to-distance between the bearings and the shape of and the axial stress on the bearings. The test results indicate that the motion types of the superstructure at large input levels can be classified into three types: the sinking type; the uplift type; and the mixed type. These behaviors depend on the relationship between the static ultimate lateral uplifting force on the superstructure and the lateral restoring characteristics of the base-isolated story. In the analysis method, bearing characteristics are represented by a macroscopic mechanical model that is expanded by adding an axial spring to an existing model. Nonlinear spring characteristics are used for its rotational, shear, and axial spring. The central difference method is applied to solve the equation of motion. To verify the validity of the method, simulation analysis of the shaking table tests are carried out. The results of the analysis agree well with the test results. The proposed model can express the buckling behavior of bearings in the large deformation range.

To grasp the effects of creep characteristics and rising temperatures on lead rubber bearings under wind load, long-duration cyclic loading tests and real-time online tests were conducted. From the loading tests, the lateral restoring characteristics of the lead rubber bearings in the small deformation range considering the creep characteristics were obtained. Analytical results using a simplified estimation method considering the small deformation characteristics of lead rubber bearings agreed well with the test results. From the online tests, the response properties of a base-isolated building under wind load were experimentally verified, and the validity of the modeling approach for lead rubber bearings and the wind response analysis method were confirmed.

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This paper presents evaluation of the influence on the seismic response of the structures base-isolated with High-Damping Rubber Bearings (HDB) under long-duration, and long-period earthquake motion. The dynamic properties of HDB, such as horizontal stiffness and equivalent damping ratio, are affected by heat in the rubber due to energy absorption during earthquake. In this study, relation of absorbed energy to dynamic properties is investigated by dynamic cyclic-loading test of HDB with large amplitude, and empirical equations are proposed. Additionally, seismic response analysis, under long-period earthquake motion is conducted and the influence of the heat-mechanics interaction of HDB on the response of the structure is evaluated.