混凝土连续箱梁桥拼接拓宽后箱梁顶板病害分析

为探讨桥梁横向拼接拓宽给既有预应力混凝土箱梁桥箱梁桥面板可能带来的结构病害，利用有限元方法分析新旧箱梁之间产生的相互作用以及对既有箱梁结构应力状态的影响，研究既有箱梁顶板和翼缘板在拓宽后可能产生的结构病害及其产生的机理。结构分析中考虑的主要参数包括新建混凝土桥梁的收缩及徐变效应、新旧箱梁之间的不均匀沉降差、温度梯度以及车辆活载作用。研究结果表明：拓宽后既有箱梁的部分顶板和靠近新建箱梁的大部分内侧翼缘板顶面普遍处于较大的拉应力状态，其中新建桥梁混凝土收缩和徐变效应、新旧箱梁之间的不均匀沉降差是主要原因，将很可能造成翼缘板上翼缘大部分区域开裂，设计时需采取相应加固措施，并建议了箱梁桥面板横向加固方法；拓宽后新旧箱梁整体结构在梁端截面将发生较大的横向偏移变形，极有可能挤压侧向抗震挡块，造成结构损害，因此有必要限制需拓宽的混凝土连续箱梁桥总长；应重视以往桥梁拓宽设计时忽视的箱梁桥面板横向应力状态变化及其可能带来的结构病害，设计者应充分注意桥梁拓宽所带来的不利影响。

Research on Structural Diseases Due to a Joint Widening of Concrete Continuous Box Girder Bridge

In order to investigate the possible structural diseases brought to the bridge deck of the existing prestressed concrete box girder bridge, the interaction between the old and new box girder after widening and the stress state of the existing box girder before and after widening were analyzed using finite element method in this paper. And the possible structural diseases and their mechanisms that were brought to the roof and flange plate of the existing bridge were studied. The main parameters considered include the shrinkage and creep effect of the new concrete bridge, the uneven settlement difference between the old and the new box girder, the temperature gradient and the vehicle live load. The results showed that part of the roof and the inner flange of the old box girder were generally in the state of large tensile stress, the main reason for which was the shrinkage and creep effect of the new concrete bridge and the uneven settlement difference between the old and the new box girder. And the stress value was larger than the value of the C50 concrete tensile strength, which would most likely cause crack on the flange plate. Hence, the design needs to take reinforcement measures. Meanwhile, the larger transverse displacement deformation of the overall box girder structure in the beam end section, had exceeded the distance between anti-seismic stop and the web in the beam end, which would most likely squeeze anti-seismic stop, resulting in structural damage. Therefore, it is necessary to limit the length of continuous box girder bridge which needs to be widened. At the end of this paper, a new measures is put forward to solve the problem that laying the reinforcement steel strand on the inner flange plate of the old bridge.