The complex terrain and expanding transport networks in Southwest China have heightened the demand for valley‐spanning bridges in active fault zones, posing seismic design challenges. This study investigates the seismic response of a near‐fault valley‐spanning bridge using deterministic ground motion simulations of reverse fault rupture. The goal is to evaluate whether the common seismic design assumption that horizontal and vertical ground motions can be represented by SV and P waves is consistent with actual conditions represented by the fully 3D waveform solution and to assess the validity of assuming Rayleigh waves as input waves. Results indicate significant differences in the internal forces. Axial force distribution varied: The fully 3D waveform solution and Rayleigh wave caused peak axial forces near the arch crown and arch foot, while the P–SV wave caused peaks mainly near the arch foot. Analysis of transfer functions for axial forces at the arch foot revealed that these differences are attributed to variations in the dominant mode shapes excited by different inputs: The fully 3D waveform solution predominantly excited longitudinal and transverse rotational modes, Rayleigh wave primarily excited transverse rotational modes, and P–SV wave mainly excited longitudinal and vertical modes. These findings underscore that treating seismic motions as single Rayleigh or P–SV waves may cause overestimation or underestimation of the structural response. Therefore, the fully 3D waveform solution is recommended for reliable near‐fault seismic response assessment and design of valley‐spanning bridges in complex terrain.
Luo et al. (Sun,) studied this question.