Performance and Limitations of Real-Time Hybrid Simulation with Nonlinear Computational Substructures

Hybrid simulation (HS) and real-time HS (RTHS) are widely used experimental techniques to evaluate the seismic performance of structural components and full systems. The goal of this study is to investigate the performance and limitations of RTHS when the computational model involves complex and highly nonlinear behavior, mainly due to both stiffness and strength deterioration. To establish the case of deploying such heavily nonlinear models, a RTHS methodology is presented to study the effect of using braces for seismic retrofitting of older steel moment resisting frames (MRFs). The objective of this paper is two-fold. First, assess the performance and identify limitations of integration algorithms for RTHS with heavily nonlinear models. Second, demonstrate the feasibility of HS/RTHS testing for selecting the best seismic retrofitting strategies. A comprehensive analytical study of different MRFs models is presented to study the performance of different integration algorithms available in OpenSees. Selected MRF model is modified to conduct a series of nonlinear RTHS tests using a compact HS test setup at the University of Nevada, Rene. The performance of two implicit and explicit integration algorithms is assessed for RTHS, and the quality of HS results from RTHS and slow HS tests are compared. Moreover, a demonstration of how HS could be used for assessing best seismic retrofitting strategies based on realistic nonlinear models is presented.