Fast hybrid test system for substructure evaluation

This study concerns the development of the Fast Hybrid Test (FHT) system at the University of Colorado-Boulder, as part of the George E. Brown, Jr. Network for Earthquake Engineering Simulation (NEES).; The FHT system is based on the conventional pseudodynamic test method, which combines physical testing with numerical simulation. A substructuring concept is adopted ill this system so that only a part of the structural system with expected inelastic responses is physically tested while the rest is simulated in a computer. The main distinction of this new system from a conventional pseudodynamic test system is the fact that its actuators move in a high speed continuous motion. A test can be conducted at the same rate as in real-world earthquake responses. This system adopted an unconditionally stable implicit time integration scheme. Such a method provides a robust computational environment for the simulation of large-scale structural systems. A linear restoring force correction method is applied to the iterative steps to help avoid the effect of displacement phase lag between analytical degrees of freedom and experimental ones as a result of actuator delay and/or other experimental errors. The scheme has been implemented in a general finite element software framework OpenSees running on a real-time operation system to ensure precise actuator control, and a smooth dynamic actuator motion. With this system, alternative time integration schemes may also be implemented.; An overview of the system, formulations of implicit time integration schemes used, and their implementations will be presented here. Simulations and substructuring tests have been conducted in its verification. Results are compared with those from numerical analyses.; The Fast Hybrid Test System developed is an effective new system for high speed continuous pseudodynamic tests in seismic performance evaluations of large scale structural systems.