考虑收缩、徐变和松弛相互影响的预应力长期损失计算

Calculation of Long-torm Prestress Loss Considering Interaction between Shrinkage,Creep and Relaxation

由于混凝土的收缩、徐变和预应力筋松弛的影响,会产生截面应力重分布,使得混凝土的预压应力减少,预应力筋的拉应力降低。若对预应力长期损失预测得不准确,会引发桥梁运营后工作状况的劣化,如混凝土的开裂和过大的下挠或上拱。文章考虑混凝土收缩、徐变和预应力筋松弛三者相互影响,考虑了非预应力筋重心和预应力筋重心不重合的一般情况,推导了预应力长期时变损失的计算公式,并与试验结果及现桥规进行了比较,最后对桥规中计算预应力长期损失的方法提出了改进建议。

Compression in concrete and tension in prestressing steel will reduce gradually because of creep and shrinkage of concrete and relaxation of prestressing steel.Inaccurate prediction of long-term prestress losses can cause serviceability problems,including concrete crack and excessive deflection or camber.Taking account of the interaction of concrete shrinkage,creep and relaxation of prestressing tendons,the equation of long-term prestress losses was deduced when the layer of centroid of non-prestressed steel was different with centroid of tendons.Then,comparison between theoretical values and experimental results showed that the presented equation achieved higher accuracy.Some recommendations for the calculation of prestress losses are given to improve the present code.