Equivalent Force Control Method for Real-time Testing of Nonlinear Structures |
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Authors: | Bin Wu Guoshan Xu P Benson Shing |
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Institution: | 1. School of Civil Engineering , Harbin Institute of Technology , Harbin, China bin.wu@hit.edu.cn;3. School of Civil Engineering , Harbin Institute of Technology , Harbin, China;4. Department of Structural Engineering , University of California at San Diego , San Diego, California |
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Abstract: | The equivalent force control (EFC) method replaces numerical iteration with a feedback control strategy to solve the nonlinear equations of motion using an implicit integration method for real-time substructure tests (RSTs). The method, however, requires the conversion of the equivalent forces to structural displacements using a conversion matrix. It is demonstrated in this article that with the use of a proportional-integral (PI) controller for the EFC, one has the convenience of choosing the initial stiffness matrix of a structure to construct the conversion matrix regardless of the properties and degree of nonlinearity of the system. The stability condition of the EFC using a PI controller has been derived with the Routh stability criterion. Methods for designing and tuning a PI controller for RST using EFC have been presented and excellent system performance has been obtained from numerical simulations and actual tests. The simulation results showed that the EFC method using a PI controller and the initial stiffness matrix to construct the conversion matrix can deliver excellent performance even for structural systems that develop a severe strain-softening behavior. Its superiority over iteration method proposed by Jung et al. 2007] Jung, R. Y., Shing, P. B., Stauffer, E. and Thoen, B. 2007. Performance of a real-time pseudo dynamic test system considering nonlinear structural response. Earthquake Engineering and Structural Dynamics, 36: 1785–1809. Google Scholar] was demonstrated through numerical simulation. This provides an efficient means to test nonlinear multiple-degrees-of-freedom structures. |
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Keywords: | Real-time Substructure Testing Equivalent Force Control Method Proportional-integral Controller Pseudo-dynamic Tests Iteration |
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