拱桥吊杆安全性加固改造方案设计研究

Study of Safety Reinforcement and Rehabilitation Scheme for Arch Bridge Hangers

部分早期建设的吊杆拱桥因设计理念、技术等限制,吊杆上、下端分别固结于拱肋及主梁混凝土内,为不可更换构件,且吊杆运营状况难以检查。为改善这类拱桥吊杆受力状态,确保结构安全性能,以某下承式钢管混凝土拱桥为背景,进行吊杆安全性加固改造方案设计研究。加固设计时,在2根旧吊杆(采用19-∅j15 mm抗拉强度270 ksi低松弛钢绞线)之间增设1根吊杆(采用37-∅s15.2 mm抗拉强度1960 MPa高强度钢绞线),新吊杆按恒载状态下各吊点3根吊杆内力相当的原则设计,新吊杆及其锚固结构为可更换构造。通过不同工况下有限元模型计算分析可得:采用该方案加固后,桥梁结构受力状态保持不变,结构安全性显著提高;在新、旧吊杆共同受力的状态下,旧吊杆安全系数约为原设计的1.5倍,新吊杆最小安全系数为6.3;旧吊杆完全失效的极端工况下,新吊杆承载能力满足受力需求。

Due to the design philosophy and technical limitations,in some early arch bridges with hangers,the upper and lower ends of hangers are fixed to the concrete of arch ribs and main girder,which are assessed as irreplaceable components.The service conditions of these hangers are usually difficult to predict.Based on a through concrete-filled steel tubular arch bridge,the safety reinforcement and rehabilitation schemes for bridge of such type is studied,to figure out ways to improve the load bearing capacity of the hangers and structural safety of arch bridges of similar type.In the strengthening of the example bridge,a new hanger(containing 37,∅s15.2 mm high-strength steel strands,with tensile strength of 1960 MPa)is added between two old hangers(each comprising 19,∅j15 mm low relaxation steel strands,with tensile strength of 270 ksi).The new hangers are designed with load bearing capacity equivalent to the internal forces of three hangers at each suspension point under static loads,and the new hangers and their anchor structures are replaceable.The finite element model analyses carried out under different load cases show that the load bearing behavior of the bridge remains the same after strengthening,and the structural safety of the bridge has been greatly improved.With the synergy of the old and new hangers,the safety factor of the old hangers has been 1.5 times of the original value,and the minimum safety factor of the new hangers is 6.3.The load bearing capacity of new hangers could meet the requirements even when all the old hangers are deficient.