Study on dynamic response analysis of a long-span and asymmetrical suspension bridge subjected to uniform and nonuniform ground motions

This study investigates the dynamic response of large-span asymmetric suspension bridges under spatially varying seismic motion, focusing on a representative bridge in Yunnan, China. A 3D finite-element model of the bridge was created using SAP2000, accounting for the sag effect of main cables and pile-soil interaction. The material nonlinearity was incorporated through plastic hinges, with critical parameters derived from XTRACT software. Based on nonlinear time history analysis under spatially varying seismic motion, the effects of spatial variability and material nonlinearity on key structural responses (shear force, bending moment, and displacement) were systematically investigated. The results indicate that considering the traveling wave effect and material nonlinearity will increase the foundation shear force and bending moment values. Under multipoint excitation, the peak longitudinal and mid-span vertical displacements are approximately 1.61 times and 1.64 times higher than those without considering the traveling wave effect and material nonlinearity, respectively. Moreover, the axial force of the suspension rod is significantly increased due to the influence of high-order modes of the bridge structure. Material nonlinearity at the tower base reduces displacement response. Neglecting these factors would underestimate earthquake effects. These findings are valuable for the design and engineering of large-span asymmetric suspension bridges.