Response of latticed shell subjected to uniform and spatially varying spectrum-matched seismic ground motion excitations

Abstract

Seismic design of latticed shell structures requires the use of structural analysis results obtained by using the design spectrum-matched ground motion records. As finding such records from the database of the actual recorded ground motions is often difficult, synthetic spectrum-matched ground motions are often employed. It is noted that for large span structures such as lattice shells, each of its supports could experience (partially) time-frequency dependent coherent ground motion excitations, including the wave passage effects. The partially coherent and spatially varying spectrum-matched ground motions may influence the peak seismic responses. However, the investigation of such an influence has not been investigated. This is partly due to the unavailability of a popular algorithm to sample such spectrum-matched records.

In the present study, an algorithm to simulate spatially varying spectrum-matched ground motions is proposed based on Fourier transform and S transform (ST). The proposed algorithm iteratively edits the ST coefficient. It also involves the use of a recently developed iterative power and amplitude correction (IPAC) algorithm that is capable of generating multivariate (partially) coherent nonstationary non-Gaussian processes. The use of the proposed algorithm results in simulated records that match the prescribed design spectra and coherence function. Sets of spatially varying spectrum-matched records are simulated and used to assess the seismic response of a latticed spherical shell. The obtained results are compared with those obtained by considering fully coherent spectrum-matched records. The comparison indicates that the consideration of spectrum-matched records with prescribed time and spatially varying characteristics can influence the seismic peak response of latticed spherical shell. This implies one may need to consider such an influence for the seismic design of large-span latticed structures.