5×25 m简支转连续箱梁桥部分支座更换引起的附加应力分析

Analysis of Additional Stress Caused by Partial Bearings Replacement of the 5×25 m Simply Supported-Continuous Small Box Girder Bridges

摘要:

针对5×25 m的简支转连续箱梁桥仅中间1墩或2墩上板式橡胶支座需更换的情况，采用横向同步、纵向单墩或2墩同时顶升是比较合理的施工方案。为了保证顶升施工中不出现梁体应力超限问题，建立梁格模型，采用数值模拟方法分析了顶升高度和横向不同步对桥梁上部结构应力的影响。结果表明：横向同步时，顶升相同高度，单墩顶升在梁体上产生的附加应力超过2墩同时顶升产生的附加应力；2种顶升模式下，梁体附加应力最大值，包括最大拉应力和最大压应力均随着顶升高度的增加而增加，且呈线性变化；根据数值计算结果，建立了梁体截面最大拉应力和最大压应力随顶升高度变化的拟合公式；在单墩顶升高度为5 mm、横向不同步量值设为0.3 mm的4种不同步顶升工况下，梁体在顶升点处的截面最大附加拉应力和压应力分别为0.580、-1.050 MPa，较同步顶升时分别增加23.9%和27.4%。在顶升限值容许的情况下，建议优先采用逐墩（单墩）顶升方式。

Abstract:

Considering that only the plate rubber bearing on the middle pier or two piers needs to be replaced, the longitudinal single pier or two pier jacking construction scheme is more reasonable than the overall jacking. In order to avoid the stress overrun of the beam during the jacking construction, the influence of the jacking height and the lateral unsynchronization on the stress of the superstructure is analyzed by using the numerical simulation method based on the grillage model. The results show that the additional stress caused by single pier jacking is greater than that caused by two piers jacking at the same height. The additional maximum tensile stress and the additional maximum compressive stress in the two jacking modes increase with the increase of the lifting height and change linearly. According to the results of numerical calculation, the relation formula between the maximum additional tensile stress, the maximum additional compressive stress and the lifting height is proposed. When the lifting height is 5 mm and the height difference is 0.3 mm, the maximum additional tensile stress and compressive stress at the section of the jacking pier are 0.580 MPa and - 1.050 MPa respectively, which are 23.9% and 27.4% higher than those of the synchronous lifting.