A simple approach to estimate physical parameters of singledegree- of-freedom structures under earthquake excitations

This study introduces simple piece-wise linearization in time series (SPLiTS) that is developed to estimate physical parameters of nonlinear structures based on a time-domain inversion. SPLiTS regards a nonlinear structure to be a set of piecewise linearised structures, based on each half-cycle wave in the displacement response data. SPLiTS minimises the effect of the central-point shift in displacement response data. It selects effective data for parameter estimations, by employing three thresholds for the displacement and velocity response data as well as the number of steps consisting of each half cyclic wave. Then, response data (acceleration, velocity and displacement and external force applied to the structures) processed by SPLiTS is applied to the time domain inversion to estimate physical parameter of the nonlinear structures. In this study, SPLiTS was applied to experimental data obtained from shaking table tests, in which a specimen imitating a one-storey structure clearly displayed inelastic behaviour. SPLiTS reasonably estimated its physical parameters that show increased damping and decreased stiffness in time series at the occurrence of yielding. This experimental verification demonstrated that SPLiTS is applicable to physical parameter estimations of structures damaged by earthquake excitations.