钢桁架桥斜拉杆螺栓裂纹尖端三维应力场研究

摘要

A refined 3-D fracture mechanics model containing a crack around a bolt hole is established for a simple-supported steel truss bridge ,the crack growth is simulated ,and the stress field near crack vicinity are studied ,then the principal tensile stress ,the stress intensity and M ISES stress a-long three directions were analyzed ,and the relation curve of Tz (out-of-plane constraint factor ) and r/t (distance from the crack tip/thickness) was fitted .It turned out that the stress concentration fac-tor was greater than 4 and the out-of-plane constraint was occurred only in the coverage of 0 .6 times the plate thickness near crack .%运用有限元分析软件建立了钢桁架桥三维仿真模型，研究受拉力最大的斜拉杆螺栓裂纹尖端空间应力场，分析了主拉应力、应力强度和van Mises应力沿三个方向的变化规律，并拟合得到离面约束因子Tz与r/t（距裂尖距离/板厚）之间的关系式。研究结果显示裂纹尖端应力集中现象突出，应力集中系数大于4；裂纹表面与内部的扩展前沿不一致，斜拉杆翼缘板偏桁架外侧裂纹扩展更快，易在螺帽内形成具有隐蔽性的类椭圆裂纹；三维应力约束的影响范围在板厚的60％以内。