中文摘要：

将超千米级斜拉桥的索力优化问题归结为非线性隐式优化的数学模型，以系统最小弯压应变能为目标，根据合理成桥状态指定各种非线性约束条件，利用投影梯度法进行优化问题的求解，求解过程中充分考虑了各种几何非线性的影响．采用ANSYS工具建立了1400m斜拉桥的有限元模型，然后据此建立斜拉索索力优化的数学模型，并进行优化计算．结果表明：优化前后索力的相对改变量并不大，但是结构内力状态却得到了极大改善，塔梁恒载弯矩和主梁恒载挠度明显减小，主塔塔顶向岸侧有一定偏移量，对混凝土塔的长期受力更加有利．

英文摘要：

In this paper, the cable force optimization of cable-stayed bridges with ultra kilometer span is equated as a nonlinear implicit optimization model. Then, by taking the minimum bending strain energy as the optimization object and by determining the nonlinear constraints according to the reasonable finished dead state, the model is solved via the projection gradient method, with all kinds of geometric nonlinearity being fully considered. Moreover, a finite element model of a cable-stayed bridge with the span of 1400 m is established based on ANSYS and is used to establish a mathematical optimization model of cable force. Calculated resuhs show that, after the optimiza- tion, the cable force slightly changes, yet the internal force state under dead load remarkably improves, the bending moment of girder and pylon as well as the deflection of girder significantly decreases, and the deformation of pylon migrates towards the shore side. All these variations contribute favorably to the concrete pylon under longterm loads.