泸州沱江四桥主桥扭转、剪力滞效应及关键构造研究

Research of Torsion,Shear Lag Effect and Critical Structures of Main Bridge of Fourth Luzhou Tuojiang River Bridge

泸州沱江四桥主桥为(55+200+58+50)m独塔双索面混合梁斜拉桥,桥宽49m。该桥近期为双向8车道公路桥,远期将改建为双向6车道+2线轨道交通公轨两用桥。为满足该桥近期及远期运营要求,采用有限元法对其设计关键技术进行研究:建立空间有限元脊刺骨模型,研究主梁在偏载作用下的扭转特性;建立钢箱梁和混凝土箱梁的空间有限元模型,分析其剪力滞效应;通过3个方案的对比确定主梁钢-混结合段的位置,并对其进行构造优化;通过计算分析,研究外露型钢锚箱组合索塔锚固结构的受力特性。结果表明,偏载作用下主梁最大剪应力和扭转角均满足规范要求;钢梁的剪力滞效应比较显著,混凝土梁的剪力滞效应相对不显著;钢-混结合段设于中跨侧距桥塔中心8.5m处,变形和内力均较小;采用新型钢-混组合索塔锚固结构,能充分发挥材料特性,保证桥塔安全性能。

The main bridge of the Fourth Luzhou Tuojiang River Bridge is a hybrid girder cable-stayed bridge with a single pylon, double cable planes and with span arrangement （55＋200 ＋ 58 ＋ 50） m and deck width of 49 m. In the recent future, the bridge will serve as a dual 4-lane roadway bridge and in the far future, will be retrofitted into a dual 3_lane＋2_track road-cum-light rail bridge. To satisfy the operation of the bridge in both the recent and far future, the critical design techniques of the bridge were researched, using the finite element method. The spatial spine beam model for the bridge was established and the torsional characteristics of the main girder under the eccentric load were studied. The spatial finite element model for the steel and concrete box girders was also established and the shear lag effect of the girders was analyzed. Through the comparison of the 3 schemes prepared for the girders, the location of the steel and concrete joint section of the main girder was determined and the joint section was structurally optimized and through the calculation and analysis, the mechanical properties of the exposing type steel anchor box anchorage structure in the steel and concrete composite pylon of the bridge were studied. The results demonstrate that under the eccentric load, the maximum shear stress and torsional angle of the main girder can satisfy the relevant requirements in the codes. The shear lag effect of the steel box girder is obvious, but the effect of the concrete box girder is relatively not. When the joint section is arranged at 8. 5 m from the pylon center on the side of the central span, the deformation and internal forces of the section are little. The utilization of the new type of the anchorage structure in the composite pylon of the bridge can bring the material properties into full play and can ensure the safety of the pylon.