移动载荷作用下斜拉桥结构的动态响应计算分析

运用斜拉桥的近似分析方法，将漂浮体系的斜拉桥结构简化成两端简支且中间离散弹性支撑梁、变地基系数梁和均匀地基系数地基梁三种模型。建立了移动载荷作用下斜拉桥结构的动力学方程，用四阶龙格库塔法对动力学方程进行了计算，对三种模型的固有频率和三种模型在相同移动载荷作用下的动态响应进行了比较，并对移动载荷移动速度、垂直振动的刚度和阻尼对桥梁动态响应的影响进行分析。结果表明，当拉索等效弹性系数较小时，三种模型的固有频率和挠度曲线差别较小，当拉索等效弹性系数较大时，三种模型的固有频率和挠度曲线差别明显；桥梁动态响应的频谱由桥梁的固有频率和移动载荷的自振频率组成；移动载荷垂直振动的刚度越大，阻尼越小，桥梁振动的响应越大。

Dynamic Response Analysis of Cable-stayed Bridges Subjected to Moving Load

By using the approximate analysis method of cable-stayed bridge, the cable-stayed bridge of floating system is simplified into three models： a beam supported by discrete springs, a beam on an continuous elastic foundation, and a beam on an elastic continuous foundation with variable foundation coefficients. The dynamic equation of the cable-stayed bridge structure under moving load is established and solved by the forth-order Runge-Kutta method. The natural frequencies and dynamic responses of the three models are compared one another. The results show that when the equivalent elastic coefficient of the cable is small, both the difference of natural frequency and the difference of deflection of the three models are small;and when it is large, the differences are also large. The effects of velocity, stiffness and damping of the moving load on the dynamic responses of the bridge are analyzed. The results show that, the spectrum of the dynamic responses of the bridge consists of natural frequency of the bridge and the self-vibration frequency of the moving load. When the stiffness of the moving load is large or the damping is small, the responses of the bridge are great.