顶推施工中支座脱空对混凝土箱梁受力性能的影响分析

在顶推施工过程中,由于滑道高程控制不精确、施工管理不当等因素会导致支座脱空,从而导致支反力的重分布,某些支座支反力必然增加,在支撑位置附近局部应力会比较突出,所以有必要研究支座脱空对混凝土箱梁受力性能的影响。结合某预应力混凝土连续箱梁桥顶推施工实例,通过建立三维有限元实体模型,选取某工况下的支座发生脱空进行分析。计算结果表明:支座脱空对支座支反力及箱梁的局部应力影响比较大,减小了顶板受拉和底板的受压安全储备,梁体下挠位移增大,增加了摩阻力,应在施工过程中严密监控支座,避免发生支座脱空。

Influences of Bearing Cavity on the Mechanic Performance of Concrete Box Girder during Incremental Launching

During incremental launching, the inaccurate control of slide elevation and improper construction management may lead to bearing disengaging,which results in redistribution of the reactionforce and inevitable increase of some support reaction,thus,local stress is obvious near the support location. So it is necessary to study theeffect of the bearing disengagement on the mechanic performance of the concrete box girders. Based on the practice of incremental launching of a certain pre-stressed concrete continuous box girder bridge,a three-dimension finite element solid model is established and bearing disengagements under certain working conditions are analyzed. The results of the calculation indicate that the influence of bearing cavity on support reactions of concrete box girders and the local stress is relatively remarkable and the safety reservation of the roof and floor is reduced,and the beam displacement is enlarged and friction is increased as a consequence. Thus,bearings should be closely monitored in the construction process to avoid bearing cavity.