基于变形协调原理的多塔斜拉桥竖向刚度分析

Analysis of vertical stiffness of multi-tower cable-stayed bridge based on principle of deformation coordination

为深入探寻多塔斜拉桥的刚度特征、分析多塔斜拉桥结构力学特性,选取多塔斜拉桥的最典型形式——三塔斜拉桥,基于变形协调原理,求解单位荷载作用下多塔斜拉桥的拉索竖向弹性支承刚度公式,对推导的公式进行算例验证,并分析桥梁结构主要参数对拉索竖向支承刚度的影响.研究结果表明：对边塔非边跨和非边塔左跨分别施加单位荷载时,由该公式解求得的边塔非边跨跨中挠度值与有限元解之间的误差为6.27%,求得的非边塔跨中挠度值与有限元解之间的误差为5.79%.文中解的结果比有限元解偏大的主要原因是：公式解没有考虑斜拉索的垂度效应,单位荷载作用下所产生的水平力有一部分消耗在拉索的垂度效应中,但公式推导时没有考虑拉索垂度效应,导致主梁跨中挠度偏大.推导的拉索竖向支承刚度公式可以较真实地反映多塔斜拉桥的刚度特征,符合多塔斜拉桥概念设计的要求.

In order to explore the stiffness characteristics of multi-tower cable-stayed bridge,its structure features are analyzed by taking a three-tower cable-stayed bridge as research object,which is the simplest type of multi-tower cable-stayed bridge.This paper derives an analytic formula of cable-stayed bridges cable elastic support rigidity under unit load based on the principle of deformation coordination;a series of estimating formulae are obtained;and calculating outcomes are compared with that of a finite element model;and the influence of main structure parameters for cable support vertical stiffness are analyzed.The results show that on the non side span of side tower and the non side span of non side tower with unit load,the vertical deflection errors between the non side span of side tower and finite element are within 6.27%;the vertical deflection errors between the non side span of non side tower and finite element are within5.79%.The main reason of the result of the formula larger than finite element model is that the formula does not consider the sag effect of the cable.The horizontal force caused by the uniformly distributed load with non side tower has not full effect on it;apart of the consumption is in the sag effect of the cable.The formulae proposed can meet the requirements of the conceptual design,and it is suitable for the stiffnesscharacteristic of multi-tower cable-stayed bridge.