矩形钢管混凝土桁架节点应力集中特性试验研究

为研究矩形钢管混凝土桁梁桥节点的疲劳性能，开展两榀矩形钢管混凝土组合桁架节段三点弯曲试验，对试件中的K形节点应力集中系数进行测试和分析，同时，基于试验结果，对既有K形节点应力集中系数计算公式的适用性进行分析。结果表明：相比普通钢筋混凝土桥面板和传统剪力钉的构造措施，采用预应力混凝土桥面板和局部释放剪切作用的剪力钉可提高混凝土桥面板开裂荷载，但是对于桁梁承载力基本没影响；两榀矩形钢管混凝土组合桁架节点腹杆表面热点应力水平基本相当，最大值均发生在受拉腹杆焊趾侧处，由于桥面板和剪力钉构造区别，两榀矩形钢管混凝土组合桁架节点弦杆表面热点应力值不同，最大值分别发生在受拉腹杆焊趾侧处；既有K形节点应力集中系数参数计算公式适用性分析表明，Mang等建议公式计算结果偏危险，Soh等建议公式和CIDECT建议公式计算结果偏保守，Puthli等建议公式计算得到的受拉腹杆最大应力集中系数偏保守，计算得到的受压腹杆和弦杆应力集中系数偏危险，Jiang等所提建议公式计算结果与试验结果吻合最好。

Experimental study on stress concentration characteristics of joints in concrete-filled rectangular steel tubular truss

In order to investigate the fatigue behavior of the joint in concrete-filled rectangular steel tubular composite truss bridges,two girders were tested in three-point bending,and then the stress concentration factor in their K-joints was measured and analyzed.Meanwhile,the applicability of the existing stress concentration factor equations for Kjoints were validated through comparisons agianst the test results.The results show that using the prestressed concrete slab and shear studs to locally release shear action can effectively improve the cracking load,compared to the structure using reinforcement concrete slab and conventional shear studs.However,using the prestressed concrete slab and shear studs does not have contributions to ultimate bearing capacity.The joints in the two specimens have similar hot spot stress distributions in the brace with the maximum values at the tensile brace toe.Due to the differences in concrete slab and studs,the joints in the two specimens have different hot spot stress distributions in the chord with the maximum values at tensile brace toe.The validation analysis of the existing stress concentration factor equations for Kjoints demonstrates that the equations recommended by Mang et al would underestimate the stress concentration factors.The equations suggested by Soh et al and CIDECT design guide would overestimate the stress concentration factors.The equations recommended by Puthli et al would overestimate the maximum stress concentration factor at the location of tensile brace,and underestimate the maximum stress concentration at the location of compressive brace and chord.The results calculated using the equations proposed by Jiang et al have the best agreement with the test results.