TPZ/48钢箱梁式架桥机施工状态下屈曲稳定性研究

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。

Study on the Buckling Stability of TPZ/48 Steel Box Girder Type Bridge Erection Machine under Construction State

An elastoplastic finite element model was established by finite element software ANSYS for a steel box girder type bridge erection machine with long span under pouring construction state.Based on nonlinear buckling theory,displacement controlled arc-length method was adopted to load and track the equilibrium path of structure.Nonlinear buckling analysis was carried out on the structure of bridge girder erection machine with initial geometric imperfection.The ultimate bearing capacity as well the safety factors of local and overall stability of this type of bridge girder erection machine under construction state were determine through analyzing the load-displacement curves of the instability characteristic points.The ultimate bearing capacity of the bridge girder erection machine was 3 755 t,which was greater than the designed construction load 1 600 t.The safety factor of overall stability was 2.35,while that of the local stability was only 1.32.The instability occurred at the bearings,floor,diaphragm and webs of the midspan.The analysis results of nonlinear buckling and eigenvalue buckling were compared and analyzed.Results show that for complex structure,the critical load got by nonlinear buckling analysis may be greater than that got by eigenvalue buckling analysis,for the reason that after buckling happened on the local position in the structure,the load would be transferred,and the structure would still retain the overall bearing capacity.