The Effects on the Earthquake Simulation Caused by the Characteristics of the Specimen in the Shaking Table Tests-Part (2):The Effects on the Replaying Precision of the Recorded Seismic Waves and the Real-time Compensation

The specimen is assumed to be a rigid mass in the design of the shaking table control system and the primary frequency of the specimen is about 8 Hz.However,the resonant frequency of a small-middle-sized shaking table is more than 20 Hz.Therefore,there is a big difference between the specimen and the shaking table system caused by the assumption of the rigid mass for the specimen.This results in the control system operating in a narrow frequency band and poor stability reducing the replaying precision of the recorded seismic waves.In this paper,the effects on the controlling performances caused by the quality,frequency and damping ratio of the specimens are investigated and analyzed.In the results,the replaying precision of the input seismic waves which the frequency is near the one of the specimen are poor,some of the inputs are amplified,and others are reduced.The maximum value is amplified more than 3 times compared to the input waves.For improving the above disadvantages caused by the interaction between the specimen and the shaking table,the real-time compensation of reaction algorithm is proposed for modifying the control performance.The replaying precision of the input seismic records is greatly improved under the good stability of the control system.