连续刚构桥四点合龙顶推下箱梁局部受力分析

Local Force Analysis of Box Girder of Continuous Rigid Frame Bridge Considering Closure Four-Point Thrust

大跨连续刚构桥合龙阶段往往采用顶推技术减少或消除运营中墩顶的纵向偏位,但较大的顶推力可能引发混凝土箱梁局部开裂。针对这一问题,提出四点同步合龙顶推方法,并以西北某特大连续刚构桥为工程背景,通过有限元分析传统两点顶推和所提四点顶推方式下箱梁截面局部受力和变形规律,并分析钢垫板位置、高度及加载方式对箱梁局部受力的影响。分析结果表明,在5 000 kN顶推力作用下传统两点顶推将使箱梁局部主拉应力高达4.78 MPa,而四点顶推方式应力分布更均匀,满足顶推过程中箱梁局部受力要求,且可通过钢垫板位置、高度及加载方式优化进一步减少箱梁局部受力,为同类工程合龙顶推提供可借鉴的施工新方法。

The long-span continuous rigid frame bridge is often used to reduce or eliminate the longitudinal offset of the pier roof during operation, but the larger top thrust may cause local cracking of the concrete box girder. Aiming at this problem, the four-point synchronous jacking method of closure is proposed, and a special continuous rigid frame bridge in northwest is taken as the engineering background. The local force and deformation law of the box girder section are analyzed by finite element method under the traditional two-point push and the four-point push method. The analysis results show that under the action of 5 000 kN top thrust, the traditional two-point pushing will make the local tensile stress of the box girder up to 4.78 MPa. The four-point pushing method has a more uniform stress distribution and meets the local stress requirements of the box girder during the jacking process. Moreover, the local force of the box girder can be further reduced by optimizing the position, height and loading mode of the steel pad, and a new construction method can be provided for the similar project.