Simplified procedure for simulating artificial non-stationary multi-point earthquake accelerograms

Abstract

A simplified procedure is proposed to generate artificial non-stationary multi-point ground motion inputs for the dynamic seismic analysis of long span or large scale structures. The probability distribution parameters for the phase difference were fitted using 438 recordings selected from Center for Engineering Strong Motion Data. Then the time curve of the number of zero crossings were fitted using the same dataset. By implementation of the empirical coherency function, we simulated the non-stationary multi-point artificial ground motions given design earthquake scenario (i.e. magnitude and epicentral distance) of the target site. The generated artificial recordings successfully account for non-stationarity in both the time domain and frequency domain, and the trend of spatial correlation is consistent with the utilized coherency function. The generated artificial ground motions were then applied as multi-support excitations for dynamic time-history analysis of the 190 m continuous rigid-frame box girder bridge. Approximately 15%–30% structural response difference was observed between using multi-support excitations and uniform excitations. The vertical displacement amplitude regarding mid-span of the bridge using multi-support excitations is significantly larger than the results using the uniform excitations. For both uniform input and non-uniform input cases, it is also found that the structural response of studied bridge using fitted mean ± standard deviation time curves of number of zero crossings are smaller than the results using fitted mean time curve. The difference is largely caused by the various energy content of generated recordings that are indicated by Arias intensity. This study provides an efficient procedure to generate artificial non-stationary multi-point earthquake accelerograms without cumbersome computation cost, and could be easily implemented in engineering applications.