通过建立腹板空间分析模型,分析了竖向预应力筋作用下的各项力学效应,重点研究了弹性压缩损失、扩散角。研究结果表明,常规设计计算中没有完全把握箱梁应力分布特征,竖向预应力各项损失估计不足是腹板开裂的主要原因。桥梁施工中应对竖向预应力采取二次张拉,根据实际情况采用对竖向预应力效应进行适当折减等方法确保腹板不开裂。 Through the establishment of the web space analysis model, the mechanical effects under the action of vertical tendons are analyzed, and the elastic compression loss and diffusion angle are mainly studied. The results show that the stress distribution characteristics of the box girder are not fully understood in the conventional design and calculation, and the lack of estimation of the vertical prestress is the main reason for the web cracking. In the construction of bridge, the vertical prestressing should be taken twice, and the vertical prestressing effect should be properly reduced according to the actual situation to ensure the web is not cracked.