多塔矮塔斜拉桥合龙顶推力多目标优化研究
Closure jacking force of multi-objective optimization of multi-span extra-dosed cable-stayed bridge

刚构体系多塔矮塔斜拉桥可通过在主梁合龙前施加顶推力使桥墩向边跨侧预偏，以减小主梁收缩徐变对桥墩受力的影响。将成桥状态下的桥墩应力作为目标函数，设置约束方程控制合龙施工时的桥墩应力，利用多目标线性规划方法确定合龙顶推力。计算结果表明，采用迭代计算可考虑顶推力对混凝土收缩徐变的影响，得到的合龙顶推力可使运营阶段桥墩截面拉应力最小；合龙顶推力将改变结构的应力状态，其对主梁应力状态的影响很小，但对桥墩的应力状态改变较大，由此而产生的徐变效应不能忽略；墩底约束刚度对最优顶推力的确定有一定影响，在实际顶推合龙前应进行试顶推以修正模型的墩底约束刚度。
Horizontal jacking forces can be applied at the ends of the closure segment before the final casting for multi-span extra-dosed cable-stayed bridges to improve the stress state in the piers. In this paper, multi-objective linear programming was used to calculate the jacking forces by selecting the stress in the piers as the objective function in the service stage and the stresses at the various construction stages as constraints. The results show that the iterative calculation is convenient to consider the shrinkage and creep of concrete, and the stress of the bridge pier can be minimized at the operation stage. The jacking force will change the stress state of the structure. It has little effect to the stress state of the girder but large effect to the pier stress and the creep of concrete cannot be neglected. Since the restraints of the pier bottom have a significant effect on the determination of the optimal jacking forces, a trial jacking to revise the restraints of the pier bottom is essential