自锚式悬索桥吊索不接长体系转换方案及索鞍数值模拟

为降低自锚式悬索桥体系转换施工费用、提高施工效率、简化分析过程，以抛物线理论为依据，推导出主缆垂度的影响参数，结合各参数的可控性、敏感性，通过调整主索鞍顶推和吊杆张拉策略，提出3阶段2轮张拉吊索不接长体系转换方案。为在有限元计算时精确模拟方案中主、散索鞍施工状态，将索鞍圆心点与塔顶或散索鞍底座中心点建立刚臂和主从约束两个边界，通过激活、钝化刚臂模拟索鞍临时固定和滑移状态，通过设置索鞍圆心点强制位移模拟索鞍超顶状态。以双塔3跨和独塔2跨2座自锚式悬索桥为例，根据现场实际情况分别制定了2套吊索不接长体系转换方案，并建立有限元模型对2座桥梁体系转换过程进行模拟和分析。结果表明：自锚式悬索桥主跨是避免吊索接长的关键桥跨，主缆跨径和主缆长度是影响主缆垂度、避免吊索接长的关键可控参数；通过增大主缆初期变形可有效避免吊索接长，实施方案为张拉主跨长出段吊索使主索鞍超前就位，以改变主缆跨度；提前施工部分二期恒载、加劲梁在第1轮吊索张拉后脱架，以增加主缆弹性伸长。由2座桥梁实例分析结果可知，体系转换前期主索鞍可控滑移、超前就位，后期对称张拉桥塔两侧吊索，使主缆和主索鞍间的抗滑移安全系数和桥塔应力均变化平稳，所提方案和索鞍模拟方法达到了预期目的，可为同类型自锚式悬索桥体系转换提供参考。

System Transformation Scheme of Self-anchored Suspension Bridge of Non-extension Suspender Cables and Numerical Simulation of Cable Saddle

To reduce the construction cost, improve the construction efficiency and simplify the analysis process of system transformation of a self-anchored suspension bridge, the influencing parameters of the main cable sag were derived based on the parabola theory, and by adjusting the cable saddle pushing and suspender cable tensioning strategies, a three-stage and two-round system transformation theme of non-extension suspender cables in combination with the controllability and sensitivity of each parameter was proposed. To simulate the construction status of the main and splay cable saddles in the scheme in the finite element calculation, the center point of the cable saddle and the tower top point or the center point of the splay cable saddle base were used to establish two boundaries, namely, the rigid arm and the principal and subordinate constraints. The temporary fixing and sliding status of the cable saddle were simulated by activating and deactivating the rigid arm, and the over-pushing status of the cable saddle was simulated by setting the forced displacement of the cable saddle center point. Taking two examples with a two-tower-three-span bridge and a single-tower-two-span bridge, according to the actual situation of the site, two sets of system transformation schemes of non-extension suspender cables were formulated respectively, and the FEM was established to simulate and analyze the system transformation process of the two bridges. The results of parameter analysis showed that the main span of the self-anchored suspension bridge was the key span to avoid the extension suspender cables, and the main cable span and main cable length were the key controllable parameters that affect the sag of main cables and avoid the extension suspender cables. The extension suspender cables can be effectively avoided by increasing the initial deformation of the main cable. The construction scheme was to change the span of the main cable by tensioning suspender cables to the main span longer segments to make the cable saddles reach the designated position in advance, and to increase the elastic elongation of the main cable by pouring the part of the secondary dead load and tensioning suspender cables in the first round to make the stiffening beam leave from the scaffold. The analysis results of two bridge examples showed that in the early stage of the system transformation, the main cable saddles were in the controllable slip state and the designated position in advance, and in the later period, the suspender cables on both sides of the tower were tensioned symmetrically, so that the anti-slip safety factor and the bridge tower stress changed steadily, and the establishing process of the scheme was simplified. The proposed scheme cable saddle simulation method has achieved the expected purpose, which can provide a reference for the system transformation of self-anchored suspension bridges of the same type.