Real-time hybrid simulation (RTHS) is increasingly being recognized as a powerful cyber-physical technique that offers the opportunity for system evaluation of civil structures subject to extreme dynamic loading. Advances in this field are enabling researchers to evaluate new structural components/systems in cost-effective and efficient ways, under more realistic conditions. In RTHS, the response of a structural system is simulated by partitioning it into physical and numerical substructures, and coupling at the interface is achieved by enforcing equilibrium and compatibility in real-time.
The choice of partitioning parameters will influence the overall success of the experiment. In addition, due to the dynamics of the transfer system, communication delays, and computation delays, the interaction force signals are dependent on the system state subject to delay. Thus, the transfer system dynamics must be accommodated by appropriate actuator controllers. In light of this, guidelines should be established to facilitate successful RTHS and clearly specify, (i) the minimum requirements of the transfer system control, (ii) the minimum required sampling frequency, and (iii) the most effective ways to stabilize an unstable simulation due to the limitations of the available transfer system. Moreover, to predict and evaluate the accuracy with various partitioning choices while incorporating the dynamics of the transfer system and computational/communication delays, performance indicators need to be developed.
In this study, new stability and performance indicators, predictive stability indicator (PSI) and predictive performance indicator (PPI), are proposed to predict the stability margin and performance of an RTHS system prior to its implementation. PSI and PPI assess how transfer system dynamics and computational/communication delays, which are the significant sources of systematic experimental error in RTHS, destabilize and distort RTHS responses. Moreover, along with the RTHS stability switch criterion, predictive stability and performance indicators might be used in developing acceptance criteria for conducting single-degree-of-freedom (SDOF) RTHS.
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