Report - PEER - University of California, Berkeley

This paper describes a new method of real-time dynamic seismic simulation ofstructures which involves combined use of experimentation and computation andsome of the above iteration can potentially be performed online. The newdevelopment was facilitated by the new George E. Brown Network for EarthquakeEngineering Simulation (NEES) deployment which provides unique opportunities forintegrated experimentation and computing.This novel structural simulation method involves the combined use of shaketables, actuators, and computational engines. The structure to be simulated is dividedinto one or more experimentalINTERFACE FORCESACTIVE FEEDBACK FROMand computational substructures.SIMULATED STRUCTUREAPPLIED BY ACTUATORSThe interface forces between theAGAINST REACTION WALLexperimental and computationalsubstructures are imposed byactuators and resultingdisplacements and velocities areREACTIONfed back to the computationalWALLengine (See Figure 1). TheSIMULATEDSTRUCTUREearthquake ground motion canFULL OR NEARbe applied to the experimentalFULL SCALE TESTEDSHAKING TABLESSUBSTRUCTURE(100 ton)substructures by actuators asinterpreted displacements(Pseudo-Dynamic Technique) orby one or more shakes tablesFig.1. Real-Time Hybrid Seismic Testing SystemFigure (Substructure 1. Substructure Dynamic Testing) testing.(Real-Time Dynamic Hybrid Technique). The unique aspect of the latter, the realtimedynamic hybrid system is the force-based sub-structuring. Since the shake tablesinduce inertia forces in the experimental substructures, the actuators have to beoperated in dynamic force control as well. The resulting experimental-computationalinfrastructure is more versatile than previously deployed techniques.2. COMPUTATIONAL ISSUESThe simulation of structural dynamic response became a routine in the design ofmodern construction. Most simulations are done using computational tools whichwere verified by alternative analysis techniques or by experiments. The response ofinelastic structures or other non linear systems is very difficult to assess. The timedomain numerical simulation of structures under dynamic excitation is usually carriedout by using either the modal superposition method (for elastic structures), or bydirect integration methods. Appropriate assumptions have to be made in order topredict and calculate the response of the simulated structure. In particular, the directintegration methods utilized in dynamic testing are actually performed step-by-step.Not only the analytical errors are accumulated gradually, but the selection ofsampling periods also affects the accuracy and stability of this integration process.More modern techniques based on State Space Approach (Sivaselvan and Reinhorn,260