大吨位钢箱梁顶推施工中变截面导梁的导跨比优化分析

Optimization analysis of guide span ratio of variable cross-section guide beam in the incremental launching construction of large-tonnage steel box girder

针对顶推桥梁施工中变截面导梁的最佳导跨比选取问题,以洛阳市王城大道瀍涧立交主线第七联900 t钢箱梁桥顶推工程为依托,建立顶推施工变截面导梁力学模型,利用有限元软件MIDAS-Civil分析导跨比对顶推结构内力及稳定性的影响。结果表明:当顶推进行到最大悬臂状态时,导跨比的增大有利于改善结构内力,导跨比从0.650增大到0.750时,钢箱梁的最大支反力、最大弯矩和最大应力分别降低11.36%、29.08%和29.81%;导梁末端顶推至对面墩旁支架时,钢箱梁最大弯矩和最大应力随着导跨比的增大而降低,同时因导梁长度的增长,导梁末端应力值增大;随着导跨比的增大,整体结构屈曲特征值增大,结构稳定性得到进一步提高。

In response to the issue of the selection of the optimal guide span ratio of the variable section guide beam in the construction of the launching bridge,this paper takes the launching project of the seventh 900 t steel box girder bridge on the main line of Chanjian Interchange on Wangcheng Avenue in Luoyang City as the basis to establish the mechanical model of the variable section guide beam in the launching construction,and uses the finite element software MIDAS-Civil to analyze the influence of the guide span ratio on the internal force and stability of the launching structure.The results show that the increase of the guide span ratio is beneficial to improve the internal force of the structure when the incremental launching construction reach the maximum cantilever state.And the maximum support reaction,maximum bending moment and maximum stress of the steel box girder are reduced by 11.36%,29.08%and 29.81%respectively when the guide span ratio is increased from 0.650 to 0.750.When the end of the guide beam is pushed to the support next to the opposite pier,the maximum bending moment and maximum stress of the steel box girder decrease with the increase of the guide span ratio,and the stress value of the end of the guide beam increases with the increase of the length of the guide beam.With the increase of the guide span ratio,the buckling eigenvalue of the whole structure increases,and the structural stability is further improved.