混凝土箱梁桥腹板竖向预应力筋张拉力检测方法

Method for Tension Test of Vertical Prestressing Bars in Webs of Concrete Box Girder Bridges

为解决目前普遍存在的大跨度预应力混凝土箱梁桥腹板竖向应力失效的问题,建立了竖向预应力筋外露段的动力学模型,发现了竖向预应力筋外露段锚固区刚度变化与张拉力的关系,计算了相应刚度变化与外露段固有频率关系的近似解和精确解。在此基础上进行了室内模型试验和现场试验,并在4座大桥得到应用。结果表明:所提出的检测方法原理简单,实际应用效果良好,广泛的应用将彻底改变中国大跨度混凝土箱梁桥腹板竖向预应力筋张拉力无定量测试的状况,对防止大跨度混凝土箱梁桥腹板开裂有重要意义。

In order to solve the problem that the vertical prestress widely applies in the webs of large-span concrete box girder bridges loses efficacy seriously,a dynamic model of the exposed segment of vertical prestress bar was built and a phenomenon that the flexural rigidity at anchorage zone of the exposed segment increases with the increment of effective tension retained in the bar was discovered.Subsequently,both approximate solution and exact solution on the relation of flexural rigidity and inherent frequency of the exposed segment were calculated.Based on it,indoor model test and field test which were applied to four bridges were carried out.Results show that the principle of proposed test method is easy and its practical applying effect is good.If the method is widely applied,non-quantative test state of tension of vertical prestressing bars in webs of concrete box girder bridges is totally changed.It has important significance of preventing web crack of long-span concrete box girder bridge.