Frequency response function and shaking control of the ZJU-400 geotechnical centrifuge shaker

In dynamic centrifuge modelling, shaking control is one of the key technologies and has important effects on the accuracy and repeatability of the model tests. In this study, a series of analyses and experiments is performed to study the frequency response functions (FRFs) and shaking performance of the in-flight hydraulic shaker on a geotechnical centrifuge at Zhejiang University (i.e. ZJU-400). First, based on an analytical model of the bucket-shaker-container system with interaction with the servo-hydraulic system, parametric studies on the FRF were conducted to identify the key variables in shaking control. Then a suite of dynamic centrifuge model tests were conducted under different centrifugal accelerations, payloads and shaking amplitudes, to observe the FRFs between the command and the achieved accelerations at the table. The results reveal that FRF is affected by several factors including the shaking amplitude, model parameters and centrifugal acceleration, where the shaking amplitude is the dominant factor. The FRF cluster model of the shaker was established and a feed-forward control procedure is proposed to facilitate the possibility of well-controlled shaking with only one try. The validation model tests show that the proposed procedure secures a satisfactory accuracy of the waveform replication for both sine waves and earthquake motions.