斜拉桥索塔锚固区环向预应力筋优化方法研究

Method to Optimize Hoop Prestressing Tendons in Cable-Pylon Anchorage Zones of Cable-Stayed Bridge

为防止斜拉桥索塔锚固区开裂、改善锚固区应力分布,基于遗传算法结合三维数值仿真提出一种索塔锚固区环向预应力筋优化方法,该方法利用数值仿真模型识别混凝土待优化区域,将张拉系数作为设计变量,建立数学优化模型,再结合遗传算法不断迭代优化设计变量,使索塔锚固区达到最优应力状态。以溧宁高速公路景宁高架段斜拉桥为背景,通过数值仿真和足尺模型试验,建立优化模型并采用遗传算法以锚固区应力水平为优化目标对索塔锚固区环向预应力筋进行优化迭代,并依据实测预应力损失修正优化方案。结果表明:环向预应力筋能为锚固区塔壁提供6~8 MPa的预压应力,可有效增强锚固区塔壁的抗拉能力;足尺模型试验实测预应力损失约为10%,且通过试验测得的应力值与理论计算值相吻合,数值仿真结果准确;采用最终得到的预应力方案可使索塔锚固区最大拉应力降低27.1%,有效改善锚固区应力分布状况。

This paper presents a method to optimize the hoop prestressing tendons in the cable-pylon anchorage zones of the cable-stayed bridge,aiming to prevent cracking and improve stress distribution in the anchorage zones.The method combines the 3D numerical simulation and genetic algorithm,by which,the former is conducted to identify the concrete areas requiring optimization,taking the prestressing coefficients as the design variables to build up mathematical optimization model,while the latter is used to constantly iterate and optimize the design variables,so as to achieve an optimal stress condition in the cable-pylon anchorage zones.For a cable-stayed bridge of the Liyang-Ningde Expressway,the presented method was used to optimize the hoop prestressing tendons in the cable-pylon anchorage zones,complemented with full-scale model test,and the optimization was modified by measured prestress loss.It is shown that the hoop prestressing tendons are able to provide the pylon walls in the anchorage zone with a compressive prestress of 6 to 8 MPa,to effectively improve the tensile performance of the pylon walls.The full-scale model test saw a prestress loss of 10%,and the tested stresses agreed well with the theoretical values,proving the accuracy of numerical simulation.A prestressing tendons plan was determined in accordance with the analyses,which allowed the maximum tensile stresses in the cable-pylon anchorage zones to reduce by 27.1%and effectively enhance the stress distribution in the anchorage zone.