Real-Time Error Monitoring for Hybrid Simulation. Part II: Structural Response Modification due to Errors

Hybrid simulation results have been shown to be highly sensitive to measurement and control errors associated with experimental substructures. In particular, systematic control errors due to the response lag of servohydraulic actuators can substantially modify the computed hybrid model response. This paper examines the changes in the hybrid model response resulting from experimental errors and verifies the use of hybrid simulation error monitors (HSEM) presented in a companion paper to predict these changes. The effects of a restoring force time delay on the hybrid model response are first examined by deriving a transfer function for such a system. In addition, numerical simulations of hybrid simulations with induced systematic and random errors are used to study the effects of experimental errors on the linear and nonlinear seismic response of structures. The numerical models with simulated experimental errors are then used to examine the relationship between HSEM and more common performance measures for quantifying the accuracy of the simulations. Based on these numerical studies, appropriate threshold values for HSEM can be determined to detect in real time whether the specified level of unacceptable accuracy has been exceeded in a hybrid simulation.