索塔锚固区拓扑优化拉压杆模型及预应力构造分析

Topologically Optimized Strut-and-Tie Model and Structural Analysis of Prestress for Anchorage Zone in Pylon

针对混凝土索塔锚固区承载力准确计算及预应力设计难题,提出拓扑优化拉压杆模型,以龙川枫树坝大桥为背景,采用变密度拓扑优化法构建索塔锚固区拉压杆模型,分析索塔锚固区压杆和节点的承载力、计算环向预应力需求数量,建立索塔锚固区节段有限元模型进行预应力构造优化分析,确定预应力沿高度方向布置方式、预应力盲区设计及预应力配置数量,并对优化后的模型进行应力验算。结果表明:分散布束较集中布束产生的锚固区主拉应力更小;在导管处预应力盲区增加短束可均匀提高塔侧壁的预压应力;受材料泊松效应影响,索塔锚固区预应力钢筋必须适量配置;按提出的拉压杆模型及构造优化方式布置预应力钢束可较好满足索塔锚固区受力要求。

In view of the difficulties regarding the bearing capacity accurate calculation and the prestress design for the anchorage zone in concrete pylon,the topologically optimized strutand-tie model was proposed.The Fengshuba Bridge in Longchuan was taken as an example and the strut-and-tie model for the anchorage zone in the pylon was established,using the variable density topology optimization method.The bearing capacity of the struts and nodes of the anchorage zone was analyzed and the amount of the loop prestress required by the anchorage zone was calculated.The finite element model for the segments of the anchorage zone was established as well.The structural optimization analysis of the prestress for the anchorage zone was conducted,the arrangement way of the prestress along the height,the design of the prestress blind areas and the amount of the prestress arrangement were determined and the stress calculation of the optimized model was checked.The results show that the principal tensile stress in the anchorage zone caused by the scattered arrangement of the prestressing tendons is less than that in the anchorage zone caused by the concentrated arrangement of the tendons.The adding of the short prestressing tendons to the prestress blind areas close to the prestressing ducts can uniformly improve the compressive prestress of the side walls of the pylon.Affected by the Poisson effect of the concrete materials,the prestressing tendons for the anchorage zone should be arranged in an appropriate amount.The arrangement of the prestresssing tendons according to the proposed strut-and-tie model and the described structural optimization way can well satisfy the stress requirements for the anchorage zone.