钢壁箱式钢锚梁组合索塔锚固结构受力机理与设计方法

The steel anchor beam cable-tower composite anchorage has been increasingly applied in long-span cable-stayed bridges for taking full advantage of steel and concrete materials. The main reason is that the horizontal and vertical cable forces are mostly carried by the steel anchor beam and the concrete tower, respectively. However, local tension of concrete in anchorage zone, unfavorable force condition of the joint and the complexity in construction are still critical problems. By replacing the steel bracket wallboard with steel wall box which utilizes perfobond connectors, the concrete tower in anchorage zone is wrapped and confined, and a new type of steel anchor beam cable-tower composite anchorage is proposed. The mechanical mechanism and design methods of this new anchorage structure are then investigated. Model tests under shear, tension and combined loads are conducted, and the calculation methods of bearing capacity and stiffness of perfobond connectors considering shear-tension interaction are proposed. Based on the results of experimental investigation, numerical simulation and theoretical analysis, the failure mechanism and bearing capacity of the joint of steel wall box and concrete tower under cable force and accumulated compression are investigated. Considering the slip and failure of perfobond connectors under shear and tension combined loads, nonlinear numerical simulation is conducted to reveal the mechanical mechanism of this new anchorage structure. The reasonable structure of steel anchor beam cable-tower composite anchorage with steel wall box is proposed. The calculation methods of load transfer and bearing capacity in horizontal and vertical directions of the anchorage zone are established. The construction measures to increase the crack resistance of the concrete tower are also suggested. All the findings may provide references for the application of this new anchorage structure in super long-span cable-stayed bridges.

钢锚梁组合索塔锚固结构主要由钢锚梁承担水平索力、混凝土塔壁承担竖向索力，能够充分发挥钢与混凝土材料性能，在大跨径斜拉桥中应用逐渐增多。针对锚固区混凝土局部受拉、结合部受力不利且施工复杂等问题，将钢牛腿壁板改造为设置开孔板连接件的钢壁箱，包裹并约束锚固区混凝土塔壁，提出新型钢壁箱式钢锚梁组合索塔锚固结构，并对其受力机理与设计方法展开研究。通过纯剪、纯拉及拉剪共同作用模型试验，提出开孔板连接件拉剪耦合承载力与刚度计算方法。结合模型试验、数值模拟与理论分析，研究钢壁箱与混凝土塔壁结合部在索力及累加压力荷载下的破坏机理与承载性能。考虑开孔板连接件拉剪耦合滑移及破坏机理，通过非线性数值模拟揭示钢壁箱式钢锚梁组合索塔锚固结构受力机理。提出钢壁箱式钢锚梁组合索塔锚固结构的合理构造、锚固区水平与竖向传力计算方法、承载力计算方法及混凝土塔壁抗裂构造措施，为该方案在超大跨径斜拉桥中的应用提供依据。

钢锚梁组合索塔锚固已越来越多地应用于大跨度斜拉桥，目的是由钢锚梁和混凝土塔壁分别承担水平和竖向索力，充分发挥钢和混凝土材料优势。锚固区混凝土局部受拉、节点受力不利以及施工复杂是关键问题。通过将钢壁板牛腿换成封闭钢壁箱，包裹约束锚固区混凝土塔壁，提出一种新型钢锚梁组合索塔锚固结构，并研究其受力机理和设计方法。通过纯剪、纯拉和拉剪耦合模型试验，提出了考虑拉剪耦合相互作用的开孔板连接件承载能力和刚度计算方法。基于模型试验、数值模拟和理论分析结果，研究了钢壁箱和混凝土塔壁在索力和累积压力下的破坏机制与承载性能。考虑开孔板连接件拉剪耦合作用下滑移进行非线性数值模拟，揭示该新型锚固结构传力机理，提出了钢壁箱钢锚梁组合索塔锚固结构合理构造。建立锚固区水平和竖向的荷载传递与承载力计算方法，并提出增强混凝土塔壁抗裂性能的施工措施。研究结果可为该新型锚固结构在超大跨度斜拉桥中的应用提供参考。