铁路钢桁梁纵横梁联接处裂纹成因分析及对策

Reason Analysis and Countermeasures of the Cracks at the Juncture of Longitudinal Beam and Horizontal Beam of a Railway Steel Truss Girder

为分析某铁路连续钢桁梁桥纵横梁联接处纵梁牛腿托架裂纹产生的原因,通过在已开裂和未开裂牛腿托架竖板上布置动应力测点,测试其在试验列车作用下的受力情况;另外建立有限元模型计算分析该处受力情况,得出该处裂缝是由于设计构造细节上的缺陷、桥墩不均匀沉降、活载作用等多种因素综合作用所致的疲劳裂纹,并提出改进加固措施:把牛腿托架水平板延伸至竖板根部,可有效降低其应力水平,提高其抗疲劳能力。

To analyze the reasons of the cracks occurred at the bracket of the juncture of longitudinal beam and horizontal beam of a railway steel truss girder bridge, the dynamic stress test points were arranged at the web plates of the cracked bracket and un-eracked bracket, and then the stress conditions were tested under the action of the test train. In addition, the finite element model was established to calculate the stress distribution in this bracket. It is concluded that the cracking at the bracket belongs to fatigue cracking, which was caused by the combined action of multiple factors, such as the defect of structural detail design, the uneven settlement of bridge piers, the live loads and so on. Therefore, it is suggested that the flange plate of the bracket should be extended to the end of the web plate, so as to reduce the stress level at the bracket and entrance its anti-fatigue ability effectively.