预应力钢绞线网加固混凝土桥梁的索力分布试验研究

Experimental study of distribution on prestressed strand mesh in strengthening concrete bridges

对于采用挤压头连接锚固工艺的高强钢绞线网的桥梁加固技术,为了在预加应力阶段对一次锚固得到的预应力水平与索力分布均匀程度进行便捷和高精度的监测,基于静力平衡原理推导了修正边界的钢绞线索力监测公式,并开展了两组大比例模型梁钢绞线网张拉与索力监控试验研究.试验结果表明:修正后的索力监测值与实际值的相对误差为4.6%,测试精度满足工程要求.基于索力分布统计规律开展了应力松弛试验,提出了无应力索长控制的索力修正模型,以减小钢绞线网索力分布的界限波动率,达到了一致性索力设计状态.该方法解决了狭小空间下预应力钢绞线网索力监测问题,对于后续索力调整研究及保障设计预应力水平均具有重要的意义.

For bridge reinforcement using high-strength prestressed strand mesh with extruded joint anchorage, the corrected boundary formula of stretching force for a single steel strand is derived based on static balance principle in order to monitor the stretching force and its distribution state in convenient and high-precision way once after anchorage,. Experiment on two group of large-scale PC beam models is conducted as well for the purpose of testing the method mentioned before. The test result shows that the relative error for stretching force of a single strand between monitoring value and actual one is less than 4.6 percent. Based on statistical distribution mode of stretching force and stress relaxation test, amending model on stress-free length is promoted to reduce the limited fluctuation ratio of the stretching force distribution of steel wire mesh. This method solves the problem of stretching force monitoring on prestressed strand mesh in small spaces and meets the requirement of engineering accuracy and therefore, has great significance for subsequent research of stretching force adjustment and can guarantee the expected prestressing levels.