Real-Time Hybrid Testing Using an Unconditionally Stable Explicit Integration Algorithm

A number of seismic hazard mitigation devices have been recently developed to enhance the seismic performance of structural systems. Many of these devices are load-rate dependent. The development of performance-based earthquake engineering procedures to effectively design structures with these devices requires that their behavior be well understood, accurate analytical models exist, and the design procedure be verified. These requirements can best be met by performing real-time hybrid tests of structural systems with these devices. The Real-Time Multi-Directional (RTMD) Earthquake Simulation NEES Equipment Site at Lehigh University specializes in real-time hybrid testing. This paper presents the development and application of an explicit integration algorithm for real-time testing at the RTMD facility. The algorithm is unconditionally stable for linear and nonlinear softening structures and developed using an innovative approach based on discrete control theory. This paper includes the development of the integration algorithm, its implementation into the real-time integrated control system at the RTMD facility, and its application to the real-time hybrid testing of passive elastomeric dampers. The integration algorithm is shown to be easy to implement and enable exceptional real-time hybrid test results to be acquired.