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采用有限元软件ANSYS建立某大跨度钢箱梁式架桥机在浇筑施工状态下弹塑性有限元模型。基于非线性屈曲理论,采用位移控制的弧长法加载跟踪结构平衡路径,对含初始几何缺陷的架桥机结构进行非线性屈曲分析。通过对失稳特征点的荷载—位移曲线分析,确定该型架桥机施工状态下的极限承载力、局部稳定和整体稳定的安全系数。架桥机的极限承载力为3 755t,大于设计施工荷载1 600t,整体稳定安全系数为2.35,但局部稳定安全系数仅为1.32;失稳位置发生在支座以及跨中的底板、横隔板、腹板等处。由非线性屈曲分析结果与特征值屈曲分析结果的对比分析得到:对于复杂结构,由于结构内局部发生屈曲后荷载会发生转移,其结构并未失去整体承载能力,因此由非线性屈曲分析得到的临界载荷可能大于由特征值屈曲分析得到的临界载荷。
The finite element software ANSYS was used to establish the elastic - plastic finite element model of a long span steel box girder erecting machine under pouring condition. Based on the nonlinear buckling theory, the displacement-controlled arc-length method is used to load the track of tracked structure, and nonlinear buckling analysis is carried out on the erecting machine with initial geometric defects. Through the analysis of the load-displacement curve of the characteristic points of instability, the ultimate bearing capacity, local stability and overall stability safety factor of this type of erecting machine are determined. The ultimate bearing capacity of the erecting machine is 3 755t, which is larger than the design and construction load of 1 600t. The overall stability safety factor is 2.35, but the local stability safety factor is only 1.32. The instability position occurs in the support and the mid-floor, , Webs and other places. From the results of nonlinear buckling analysis and eigenvalue buckling analysis, it is found that for complex structures, the load does not lose the overall bearing capacity due to the local buckling of the structure, so the nonlinear buckling analysis The critical load may be greater than the critical load obtained by eigenvalue buckling analysis.