沥青基灌浆料灌浆引起的结构预应力损失研究

Study on Structural Prestress Loss Caused by Bitumen-Based Grouting

以铁路桥梁常用后张法预应力混凝土简支箱梁为研究对象,运用仿真及一榀6.3 m长、内含2孔预应力孔道的后张法预应力混凝土简支梁模型试验,进行沥青基灌浆料灌浆引起预应力损失研究。结果表明:灌浆引起的预应力损失由灌浆引起的预应力钢绞线应力松弛、钢绞线与混凝土的热膨胀差和混凝土温度徐变等造成的预应力损失组成;灌浆过程中,预应力钢绞线与混凝土热膨胀差造成的预应力损失可分为灌浆初期快速增长、灌浆过程中缓慢降低、灌浆结束时快速降低和结束后缓慢降低4个阶段;试验梁在不同工况下的预应力损失实测数据与计算结果基本一致,说明本文提出的灌浆引起的结构预应力损失计算方法准确有效;不同灌浆浆体温度和灌浆持续时间条件下,灌浆引起的结构长期预应力损失比较接近,损失值较小;灌浆浆体温度为180℃、灌浆持续时间为30 min时,灌浆引起的长期预应力损失约为2.73%。

A study was conducted on the prestress loss caused by bitumen-based grouting for the post-tensioned prestressed concrete simply supported box girder commonly used in railway on the basis of finite element simulation and test with a 6.3 m long post-tensioned simply supported girder with two tensioning ducts.Results showed that the prestress loss caused by grouting consisted of that caused by stress relaxation of prestressed strand,by thermal expansion difference between strands and concrete,and by temperature-induced creep of concrete.During the process of grouting,the prestress loss caused by the thermal expansion difference between prestressed strands and concrete could be divided into four stages,namely,rapid increase at the initial stage of grouting,slow decrease during grouting,rapid decrease at the end of grouting and slow reduction after grouting.The prestress losses obtained under different working conditions for the test beam were basically consistent with the calculated results,which showed that the method for calculating the structural prestress loss caused by grouting was accurate and effective.Under different grout temperatures and grouting durations,the long-term prestress losses caused by grouting were relatively close and the loss values were small.The long-term prestress loss caused by grouting was about 2.73%under the grout temperature of 180℃with a grouting duration of 30 min.