Effects of Structural Nonlinearities on Effective Force Testing
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Date
2014-05-09
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Johns Hopkins University
Abstract
Effective force testing (EFT) provides an alternative experimental method for the dynamic testing of structures using force controlled hydraulic actuators. Previous experimental EFT research has confirmed limitation in force tracking performance for nonlinear test structures. This thesis presents a parametric study via computational simulation of EFT to investigate the resulting effects of structural nonlinearities. Two configurations for an experimental test structure are identified and implemented into a computational EFT framework using Matlab and Simulink. Force feedback control is employed through loop shaping techniques. Structural behavior is examined for linear elastic, bilinear elastic, bilinear hysteretic, and bilinear hysteretic pinching structural models. Computational simulation of EFT shows that a loop shaping controller is stable for the behavior of each model and the expected force-displacement relations are developed. However, some simulations result in instabilities for bilinear hysteretic pinching behavior. Overall, this study demonstrates that force tracking performance significantly diminishes as the structural models become highly nonlinear. This effect is evident for both test structure configurations in all three nonlinear models.
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Keywords
Effective force testing, dynamic force control, experimental methods