起重机箱型梁变截面处应力集中问题的研究

Study on Stress Concentration at the Cross Section of Crane Box Girder

针对起重机实际使用过程中常见的箱型梁变截面处弧形翼缘板与腹板角焊缝位置使用一段时间后开裂的工程失效案例,基于起重机设计规范,进行理论求解,计算了起重机设计中的剪切应力,结合实际生产经验探讨了由应力集中问题导致的开裂问题,指出截面处的突变造成了严重的应力集中问题,最终使得焊缝处应力远远大于应力的规范许用值,由此该危险截面处结构被破坏,产生了开裂问题。在理论探讨的基础上,结合应力集中曲线图分析得出如下结论:在腹板厚度c不变的情况下,过渡圆角半径r越大则应力集中系数s越大,由此可以认为在不改变c的情况下,采用适当增大r的手段有利于减小应力集中,以此减缓开裂问题的发生。

In view of the problem of cracking which often happens in the fillet weld of box girder curved flange plate and web in the actual use,the engineering case is solved from theoretical perspective based on crane design specification.Based on the shear stress calculation and actual production experience,the paper points out that the serious stress concentration at the cross section of crane box girder mak es the welding stress larger than the standard and results in cracking.By analyzing the stress concentration curve,it concludes that if the thick ness of web(c)is constant,the stress concentration coefficient(s)increases when the transition fillet radius(r)becomes bigger.Therefore,it can be concluded that the proper increase of transition fillet radius(r)can reduce the stress concentration without changing the thick ness of web(c),which can reduce the occurrence of cracking.