Identification of the mechanical subsystem of the NEES-UCSD shake table by a least-squares approach

A least-squares method is used to determine the fundamental parameters of a simple mathematical model for the mechanical subsystem of the NEES-UCSD large high performance outdoor shaking table. The parameters identified include the effective horizontal mass, the effective horizontal stiffness, and the coefficient of the classical Coulomb friction and viscous damping elements representing the various dissipative forces in the system. The values obtained for these parameters are validated by comparisons with previous results based on an alternative identification method applicable only to periodic tests and by comparisons with experimental data obtained during earthquake simulation tests and harmonic steady-state tests. The proposed identification approach works well for periodic sinusoidal and triangular tests, earthquake simulation tests, and white noise tests with table root mean square above 10% of gravity