考虑Ⅱ阶效应的刚架拱影响线

将大跨度拱桥轴压力产生的非线性问题简化为初位移与初应力的Ⅱ阶效应 ,使《桥规》研究活载作用的影响线方法得以实施 ,并得到良好的计算精度 .根据施工和成桥两阶段的实际情况 ,利用对称性修改力学计算模型的约束条件 ,过设计控制截面划分有限单元 ,导出梁单元刚度矩阵的具体形式 .应用改进的平面框架分析程序 ,等距移动半单位荷载位置 ,一次得到各种内力和挠度的影响线竖距 .分析横向分布系数后 ,计算所得活载跨中挠度与成桥静载试验值相当吻合

Influence lines for framed arch with second-order effects considered

A nonlinear problem resulted from axial compression of long-span arch bridges is simplified into the second-order effects of the initial displacement and the initial stress. Thus, the influence line approach to live-load action in the Bridge Code comes into effect and the larger accuracy is obtained. In the light of the stages of construction and completion, the constrained conditions in the calculated models are modified with symmetrization. Moreover, the framed arch is discreted into several elements in the design-governing sections. After deriving the stiffness matrices of beam element, the improved program for analysis of a plane frame is used for calculating all the vertical offsets of influence lines for the various inner force and deflection with moving a half unit load at a equidistance on a framed arch. Dealing with the lateral distribution coefficients, the resulting midspan deflection under live load on the given completed bridge coincides with the value obtained from the static load test.