铰接悬臂拼装连续梁剪力铰受力影响因素分析

Analysis on Force Influencing Factors of Shear Hinges of Hinged Cantilever Assembled Continuous Beams

剪力铰是一种只传递剪力、不传递弯矩的构造,在铁路桥梁中首次成功应用于成昆线旧庄河1号桥。剪力铰的受力较为复杂,使用过程中其主要部件预应力粗钢筋发生了多次破断。本文分析了剪力铰“左右块体+竖向预应力粗钢筋”构造,进行了外观状态检查、桥面线形测量、三向相对位移测试和粗钢筋应力测试。结果表明:部分粗钢筋管道中长期存水,导致粗钢筋存在局部锈蚀的可能;剪力铰处的桥面下挠达到118 mm,列车通过时的冲击作用明显增大;剪力铰两侧最大竖向位移差达到0.64 mm,即粗钢筋力值差为59.6 kN,接近预应力螺纹钢筋容许疲劳力值,长期疲劳荷载作用下疲劳断裂的风险加剧;粗钢筋有效预应力均高于设计值,最大值高出100%(153 kN),但远小于其极限承载力668 kN,粗钢筋发生极限承载力破坏的可能性较小。结合影响剪力铰粗钢筋破断的因素,提出了剪力铰养护维修的指导建议。

Shear hinge is a structure that transmits only shear force but not bending moment.It was successfully applied to Jiuzhuanghe 1#bridge on Chengdu-Kunming Railway for the first time in railway bridges.The stress of the shear hinge is relatively complex,and the prestressed steel bars had broken many times during last few years.This paper analyzed the structure of“left and right blocks+vertical prestressed steel bars”of shear hinge,and carries out appearance condition inspection,the bridge alignment measurement,three-dimensional relative displacement test and steel bar stress test.The results show that the long-term water storage in some pipes may lead to local corrosion.The deflection of the bridge deck at the position of the shear hinge reaches 118 mm,and the impact effect of the train passing through is significantly increased.The maximum vertical displacement between the two sides of the shear hinge reaches 0.64 mm,that is,the force difference of the steel bars is 59.6 kN,which is close to the allowable fatigue force of the prestressed steel bar,and aggravates the risk of fatigue fracture under long-term fatigue load.The effective prestress of the steel bar is higher than the design value,with a maximum of 100%(153 kN),but far less than its ultimate bearing capacity of 668 kN.The possibility of failure of the ultimate bearing capacity of the steel bar is small.Combined with the factors that affect the breaking of the steel bar of the shear hinge,the paper puts forward some guiding suggestions for the maintenance of the shear hinges.