New Method for Real-Time Hybrid Testing with a Global Iteration Strategy

In current real-time hybrid testing (RTHT), command displacement is applied to the experimental substructure and a restoring force is fed back to the integration algorithm at each time step between the numerical and physical substructures, during which synchronization must be maintained to achieve the real-time effect. These inherent characteristics in RTHT raise its requirements for the numerical integration method and make it sensitive to servohydraulic time delay. This paper proposes a new method of RTHT, GI-RTHT, in which the numerical and experimental substructures are independent without any data exchange during the duration of seismic action. This feature enables GI-RTHT to use existing advanced integration algorithms, many of which have superior stability and accuracy, just like when they are used in pure numerical simulations. Furthermore, the effect of actuator time delay on numerical integration algorithm disappears. To achieve compatibility and equilibrium at the interfaces between the substructures, an iteration is involved within the time scale of the duration of the earthquake, which is similar to the iteration solution algorithm for the equation. The stability of GI-RTHT is analyzed theoretically. The applicability and stability of GI-RTHT are evaluated based on tests on a cable-stayed bridge with 5,090 degrees of freedom and 24 nonlinear links, which is considerably larger and more complex than published models of RTHT. Excellent results are achieved in the testing. Approximate convergent solutions are reached after five iterations. This work presents a novel procedure for RTHT that is particularly suitable for systems with reusable devices/components selected as the experimental substructure. (C) 2018 American Society of Civil Engineers.