拱桥断索冲击响应模型试验与有限元分析

Model Test and Finite Element Analysis of Arch Bridge Response to Cable Failure

为研究吊杆断裂对拱桥力学性能的影响,以广州海心桥为研究对象,设计并制作了几何相似比为1∶40的缩尺模型,采用缓慢卸载索力和突然断索2种方式开展吊杆断裂试验,讨论了2种吊杆失效模式对剩余构件静、动力响应的变化规律。然后采用ANSYS软件建立了有限元模型,通过瞬态分析方法对断索过程和结构响应进行了数值模拟。试验结果表明:位于L/4拱肋处的中吊杆失效后对邻近吊杆的冲击效应最为显著;吊杆索力的重分配比例随着距离断索区域的增加而减小;对于失效吊杆左右距离相同的邻近吊杆,索体长度越短的吊杆其索力分配比例越大。拱桥跨中和L/4附近吊杆断裂后的索力可近似全部由剩余吊杆承担;靠近拱脚处吊杆失效后,其一部分索力按照重分配比例由剩余吊杆分担,另一部分通过拱梁结合段直接传递到拱肋。不同典型位置处吊杆骤断后,引起邻近2根吊杆的索力动力放大系数在1.3~1.8范围内。结果可为吊杆断裂后拱桥的结构安全评估提供参考。

A 1:40 scale model of the Guangzhou Haixin arch bridge was designed and fabricated to investigate the influence of cable failure on its structural performance.Two types of cable failure tests-slow unloading of the cable tension and sudden cutting of the cable were conducted to examine the changes in the static and dynamic responses of the remaining bridge components.A finite element model was subsequently established using the ANSYS software to simulate the cable breaking process and structural response through transient analysis.The experimental results show that a cable failure at the L/4 arch rib has the most significant impact on the neighboring cables,and the proportion of redistributed cable tension decreases with increasing distance from the failure zone.For neighboring cables at the same distance from the failed cable,the shorter the cable length,the greater the proportion of redistributed cable tension.When cables at the mid-span and L/4 positions break,their tension can be assumed to be entirely borne by the remaining cables;when cables near the arch foot break,part of their tension is redistributed by the remaining cables according to their proportionate distance while the remainder is directly transferred to the arch rib through the arch-beam connection.The dynamic amplification factor of the tension in the cables adjacent to a failed cable at different typical positions is 1.3-1.8.The results of this study can provide a reference for the structural safety assessment of arch bridges after cable failure.