Comprehensive mechanics‐based virtual model of NHERI@UCSD shake table—Uniaxial configuration and bare table condition

Abstract

AbstractA mechanics‐based virtual model of the NHERI@UCSD large high‐performance outdoor shake table (LHPOST) in its uniaxial configuration and under bare table condition is presented. The virtual model includes: (i) a reprogrammed version (i.e., virtual replica) of the actual controller, (ii) a servovalve model including servovalve spool dynamics and two independent servovalve flow nonlinearities for each of the four servovalves of the system, (iii) an actuator model for each of the two single‐ended actuators, (iv) two accumulators modeling the average supply pressure drop at the entrance of the servovalves, and (v) a one‐degree‐of‐freedom mechanical subsystem model. Based on forced vibration test results for the foundation block, it was found that the soil‐foundation compliance effects do not need to be included in the virtual model of the LHPOST. The virtual model presented is able to predict accurately the actual shake table platen response under narrow and broadband inputs with the controller gains set to the same values as on the actual shake table. Moreover, the fourth stage spool displacements and actuator driving force from actual tests are reproduced accurately by the virtual model. The mechanics‐based virtual model presented in this article can be coupled with FE models of specimens to be tested on the LHPOST and can be used to improve the signal reproduction fidelity of the LHPOST and to develop more advanced model‐based shake table controllers.