Large scale real time dynamic hybrid testing technique – Shake tables substructure testing

This paper presents the development and implementation of a novel structural testing method involving the combined use of shake tables, actuators and computational engines for the seismic simulation of structures. The structure to be simulated is divided into one or more experimental and computational substructures. The interface forces between the experimental and computational substructures are imposed by actuators and resulting displacements and velocities are fed back to the computational engine. The earthquake ground motion is applied to the experimental substructures by shake tables. The unique aspect of the above hybrid system is force-based substructuring. Since the shake tables induce inertia forces in the experimental substructures, the actuators have to be operated in dynamic force control as well, since either the force or the displacement, but not both can be controlled at a given point and at a given instant of time. The resulting testing method is more versatile than existing seismic testing methods. First the substructuring strategy and the numerical integration algorithms associated with the computational substructures are discussed along with the implementation of the computational engine. Then a new dynamic force control strategy developed for this purpose using series elasticity and displacement compensation is briefly reviewed. Issues related to time-delay compensation are also discussed. Finally, an example of a real-time hybrid test implementation, and results from this experiment are presented.