大跨径刚构桥底板崩裂破坏分析

Failure Analysis on Bottom Plate Crack of Long-span Rigid Frame Bridge

考虑了实际施工中钢束定位偏差和折线施工引起的径向力增大,对等效径向力经典计算公式进行了修正。并在此基础上,根据混凝土的弹塑性损伤本构关系,对比分析了径向力增大对底板应力在张拉前后的影响。研究结果表明,施工中引起的径向力增大会导致底板应力分层,使全界面受压底板产生局部破坏性拉应力。底板破坏后截面应力重新分布,计算所得应力分布能较好地吻合现场检测结果。后期加固应考虑应力重分布,同时对箱室底板内侧、腹板内侧也要进行加固。

Considering the radial force augmentation induced by the alter of prestressed cable distribution and polygonal stretch construction, the classical equivalent radial force calculating formula is amended. And thereby based on the amended formula, combined with concrete elastic-plastic damage constitutive relations, the practical construction status is simulated to analysis the stress distribution and the influence of stress augmentation in concrete bottom at period of before and after the prestressed cable stretched respectively. The calculating results indicate because of the stratification of the stress in the concrete bottom, destructive tensile stress emerges at the bottom margin, which is supposed to be compressive stress. The development of crack leads to stress redistribution in concrete bottom area, which can be proved sufficiently by the field measurements. Consequently, the radial force augmentation in the construction shall not be ignored and should be considered seriously in design. Reinforcements on the insides of concrete box web and bottom are necessary.