Local site effects on a high-pier railway bridge under tridirectional spatial excitations: Nonstationary stochastic analysis

• A nonstationary stochastic scheme using PEM is derived for structures under tridirectional spatial seismic motions.
• A mathematical scheme in modeling nonstationary tridirectional spatially correlated ground motions is derived.
• An absolute-response-oriented scheme of PEM is proposed and implemented on the general finite element platform.
• Effects of local site conditions and ground motion nonstationarity are studied for a high-pier railway bridge.
• Recommendations for actual design of high-pier railway bridges under tridirectional nonstationary spatial motions are drawn.

This paper presents a theoretical nonstationary stochastic analysis scheme using pseudo-excitation method (PEM) for seismic analysis of long-span structures under tridirectional spatially varying ground motions, based on which the local site effects on structural seismic response are studied for a high-pier railway bridge. An absolute-response-oriented scheme of PEM in nonstationary stochastic analysis of structure under tridirectional spatial seismic motions, in conjunction with the derived mathematical scheme in modeling tridirectional nonstationary spatially correlated ground motions, is proposed to resolve the drawbacks of conventional indirect approach. To apply the proposed theoretical approach readily in stochastic seismic analysis of complex and significant structures, this scheme is implemented and verified in a general finite element platform, and is then applied to a high-pier railway bridge under spatially varying ground motions considering the local site effect and the effect of ground motion nonstationarity. Conclusions are drawn and can be applied in the actual seismic design and analysis of high-pier railway bridges under tridirectional nonstationary multiple excitations.