The main objective of this paper is to investigate the tracking ͑signal reproduction͒ capability of the UCSD-NEES shake table system through a series of broadband and harmonic experiments with different tuning and test amplitudes. The second objective is to obtain quantitative relations between different measures of the signal reproduction error and the amplitude of the reference excitation used to tune the shake table controller. These relations can be used as guidelines in planning of future seismic tests on the UCSD-NEES shake table or on large shake tables with similar controllers. The third objective is to evaluate the effectiveness of the existing iterative correction/tuning procedure for the UCSD-NEES shake table. The final objective of the paper is to propose some improvements to the current shake table tuning practice.

SUMMARYThis paper proposes a simple conceptual mathematical model for the mechanical components of the NEES-UCSD large high-performance outdoor shaking table and focuses on the identification of the parameters of the model by using an extensive set of experimental data. An identification approach based on the measured hysteresis response is used to determine the fundamental model parameters including the effective horizontal mass, effective horizontal stiffness of the table, and the coefficients of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The effectiveness of the proposed conceptual model is verified through a comparison of analytical predictions with experimental results for various tests conducted on the system. The resulting mathematical model will be used in future studies to model the mechanical components of the shake table in a comprehensive physics-based model of the entire mechanical, hydraulic, and electronic system.

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