基于热点应力法的钢管混凝土焊接节点疲劳构造细节比较

以钢管混凝土组合桁梁桥为研究对象,总结给出基于热点应力法的节点疲劳评估流程,并对其疲劳构造细节进行研究。结果表明:在矩形空管等宽节点基础上,主管内填混凝土使得节点支、主管表面最大热点应力幅分别降低10.86%和26.51%,节点疲劳寿命提高3.78倍; 在圆形空管节点基础上,主管内填混凝土使得节点支、主管表面最大热点应力幅分别降低13.88%和16.39%,节点疲劳寿命提高2.11倍; 在主方支圆空管节点基础上,主管内填混凝土使得节点支、主管表面最大热点应力幅分别降低20.06%和29.81%,节点疲劳寿命提高1.92倍; 此外,对于矩形钢管混凝土节点,先后在主管内壁设置PBL加劲肋和腹板采用整体节点板,支管表面最大热点应力幅分别继续下降12.11%和29.20%,主管表面最大热点应力幅分别继续下降8.81%和15.64%,由此可知,改变矩形空管节点的构造细节,可以使焊趾处的应力分布趋于均匀,疲劳寿命得到显著提高; 同时,在确保各类节点几何尺寸基本相当的前提下,研究得到各类节点疲劳性能优劣次序为PBL加劲型矩形钢管混凝土焊接整体节点、PBL加劲型矩形钢管混凝土等宽节点、矩形钢管混凝土等宽节点、矩形空管等宽节点、圆形钢管混凝土节点、圆形空管节点、主方支圆钢管混凝土节点、主方支圆空管节点。

Comparison on Fatigue Structural Details of CFST Welded Joints Based on Hot Spot Stress Method

Taking the concrete-filled steel tube composite truss bridge as the research object, the fatigue evaluation process of the joints of the concrete-filled steel tube composite truss bridge based on the hot spot stress method was summarized, and the structural details of fatigue control joints of concrete filled steel tube composite truss bridge were studied. The results show that, through filling the main tube with concrete, the maximum stress amplitude of rectangular equal width branch and main tube is reduced by 10.86% and 26.51% respectively, and the fatigue life of the joints is increased by 3.78 times; the circular tubular joints, the maximum stress amplitude of branch and main tube is reduced by 13.88% and 16.39% respectively, and the fatigue life of the joints is increased by 2.11 times; the joint with square main tube and circular branch tube, the maximum stress amplitude of branch and main tube is reduced by 20.06% and 29.81% respectively, and the fatigue life of the joint is increased by 1.92 times. For rectangular steel tube joints, PBL stiffeners are set on the basis of concrete filled in the main tube, and integral gusset plate is used. As a result, the maximum hot spot stress amplitude of the branch tube further decreases by 12.11% and 29.20%, and the maximum hot spot stress amplitude of the main tube further decreases by 8.81% and 15.64%. Therefore, by improving the fatigue details of the joint composed of rectangular steel tubes of equal width, the stress distribution at the welded joint is more uniform and the fatigue life is significantly improved. At the same time, based on the premise of equal axial stiffness of the branch and main tube members, the order of the fatigue performance of the structural details of joints is as follows: the PBL stiffened concrete filled rectangular steel tube integral joint, the PBL stiffened concrete filled rectangular steel tube equal-width joint, the concrete filled rectangular steel tube equal-width joint, the rectangular steel tube equal-width joint, the concrete filled circular steel tube joint, the circular steel tube joint, the joint with concrete filled square main tube and circular branch tube, the joint with square main tube and circular branch tube.