Abstract: While the ratio between the width and the span of the girder bridge is less than 0.5(B/l≤0.5), lateral deflection curve under live load is assumed to be a straight line,then the eccentric compression method (rigid diaphragm method) is usually adopted in the calculation of load distribution on girder bridge. Further, if bending and torsion are coupling, a revised formula could be derived also. As has been proved theoretically and experimentally, the bending rigidity of diaphragms is for from absolute rigid, even under theratio of B/l≤0.5, the lateral deflection line is also curved, (Here, it is assumed to bein parabolic form.) Practically, T sections or unsymmetric I sections are often used in R.C. and P. C. girder bridges, torsional rigidities of these sections compared with bend ing can be neglected. In this paper, regardless the lateral position of live load across the bridge, the parabolic curve on lateral deflection is presumed. Applying the energy approach and principle of virtual work, a revised expression is finally reached to compute the lateral load distribution on girders. The author wishes that the derived expression can befunctioned not only for B/l≤0.5, but also extended to B/l≤1. in place of G. M, andrigid-slab method already in existence in bridge design.

摘要： 在桥宽与跨径之比小于0.5的桥跨结构中,一般认为桥梁横向挠曲线呈直线关系,则偏心受压法(或称刚性横梁法)得到广泛的应用。如果再考虑到主梁的弯扭藉合,则可推导出不同的偏心受压修正公式。理论与试验均证阴,横隔梁抗弯刚度远非绝对刚性,既使B/l≤0.5横向挠度也呈曲线(这里基本假定按两次抛物线变化规律)。而且在一般钢筋混凝土或预应力混凝土粱式桥中多采用T型或不对称I字型截面,梁自身抗扭能力不大相对于弯曲而言可以忽略不计,故可以不去考虑由于扭矩的修正。本文假定横向挠曲线,无论荷载作用位置如何均假定按二次抛物线变化规律,利用能量法及虚位移原理推导出偏心受压的修正公式(这里修正非直线的横向挠曲线的影响)。这将不仅适用于B/l≤0.5而且对于B/l≤1也可以采用,这样就扩大了修正式的适用范围,而代替计算较繁复的GM法及刚性梁法,而达到简单而实用的目的。