本文以一座大跨度公铁两用悬索桥方案为计算模型.建立了三维动力有限元模型.并对其进行自振特性的分析计算.得到了悬索桥的横向、竖向、扭转、纵向以及祸合振动的频率及振型.得出的结果必将对大跨度公铁两用悬索桥的抗震、抗风设计以及车桥动力相互作用分析奠定坚实的基础

free vibration analysis of long span bridge is the base of the earthquake and wind resistance design of bridge structures. It's also the base of the analysis of dynamic interaction response between bridges and trains. The frequencies of bridge structures arc the key parameters reflecting the free vibration features. In this paper，a long-span suspension bridge scheme is selected as calculating example，and the modal analysis is then performed to determine natural frequencies and mode shapes of lateral，vertical，torsional，longitudinal， and coupled vibrations of the bridge.