Experimental testing is an essential tool for understanding how structures respondto extreme events, thus allowing the design and construction of safer structures. Methodscurrently used to determine the behavior of structural systems subjected to dynamicloading are quasi-static, shaking-table, and hybrid (or pseudodynamic) testing. In hybridtesting, the dynamic response of the structure is calculated numerically on a computer,and then the restoring forces from the structure are obtained by applying the calculateddisplacements to a test specimen. The combination of physical testing with numericalsimulation provided by hybrid testing facilitates accurate and efficient testing of large andcomplex structural systems.Because conventional hybrid testing is executed at slow speeds, the method is notapplicable for structures with rate-dependent components (for example, devicesassociated with vibration control). To allow testing of such structures, researchers haveproposed a variation of the method called real-time hybrid testing in which theexperiment is executed in real time.Real-time hybrid testing is challenging because it requires guaranteed executionof each testing cycle within a fixed, small increment of time (typically less than 10 msec).Furthermore, unless appropriate compensation for time delays (from communication andcomputing time) and actuator dynamics is implemented, stability problems are likely tooccur during the experiment. Traditionally, researchers have lumped the effects of timedelays and actuator dynamics together and treated them as a constant time delay;techniques were then developed to compensate for this total time delay. However, thesetechniques only perform well when the delay is small compared to the fundamentalperiod of the structure.The focus of this report is to develop an approach for real-time hybrid testing thatuses model-based methods to compensate for time delays and actuator dynamics andcombines fast hardware and software (for high-speed computations and communication)with high performance hydraulic components.The studies presented in this report extend the capabilities of real-time hybridtesting by facilitating accurate testing of structural systems with larger naturalfrequencies (e.g., stiff structures or multi-degree-of-freedom systems) and handling largerdelays/lags which are typically associated with actuators with high force capacity.Furthermore, these studies demonstrate that real-time hybrid testing is an effective andpractical technique to evaluate the response of structures incorporating devices forpassive and semiactive structural control.
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