三向预应力混凝土连续箱梁桥横向加劲肋拓宽研究

Research on the Widening Design of 3-way Prestressed Concrete Continuous Box Girder Bridge

针对三向预应力混凝土箱梁桥的横向拼接难题,文章提出了一种基于横向加劲肋的新型柔性横向拼接结构。保持新旧箱梁翼缘板分离,在新旧箱梁翼缘板下侧增设沿纵向均匀设置的横向加劲肋,将新旧箱梁翼缘板连接起来,形成一种基于横向加劲肋的柔性拼接结构。依托实际工程,考虑了车辆活载、基础沉降差、新浇筑混凝土的收缩及徐变变形等多重作用,对拼接结构自身及拼接前后既有箱梁的受力状态变化规律进行了较全面的有限元分析。研究表明,拼接拓宽后结构整体刚度有明显提高,且能有效减小旧桥的活载作用效应,说明横向加劲肋能够有效连接新旧箱梁,使得拓宽结构共同受力;在新建桥梁的材料收缩及徐变效应作用下,拓宽后整体结构产生较明显的横向变形,尤其要关注梁端截面的横向变位和加劲肋主拉应力值;在基础不均匀沉降差作用下,各支点截面加劲肋存在较大的主拉应力,可能造成结构开裂损坏,需要采取有效加固措施或进一步优化设计横向加劲肋。此外,文章还研究了加劲肋尺寸参数及布置间距变化对新旧桥梁及加劲肋自身应力的影响,结果表明:柔性加劲肋拼接结构用于三向预应力混凝土连续箱梁桥横向拓宽是可行的,它为类似桥梁拓宽工程提供了一种新的可选择方案。

For the aim of solve the difficulty in 3-way PC box girder bridge widening, a new flexible horizontal stitching structure based on the transverse stiffeners is proposed. Based on a bridge widening practice, the mechanical performance of the flexible stitching structure and the existed box girder after widening is studied in detail, by considering the effect of vehicle load, foundation settlement, new concrete shrinkage and creep deformation. Research shows that the structural stiffness of the whole structure is obviously improved, and the live load effect of existed bridge can effectively be reduced, which shows that the transverse stiffener can eff Due to the effect of shrinkage and creep of new box girder, the whole widening structure produces a more obvious lateral deformation, the lateral deformation of box girder and the tensile stress of transverse stiffeners should be paid on with a particular attention at the end section. Due to the uneven foundation differential settlement, an obvious tensile stress in the transverse stiffeners is formed at each support section, and may cause a structural damage in stiffeners. In addition, the influence of the size and spacing of stiffeners on the stress of the new and old bridges and stiffeners is also studied. The results show that the flexible stiffener joint structure is feasible to broaden 3-way PC box bridge, providing a new alternative scheme for similar bridge widening.