疲劳荷载下预应力混凝土梁中钢筋应力重分布的试验研究

疲劳荷载下钢筋应力幅的准确计算对于构件疲劳寿命验算具有重要意义。通过6片同时配有钢绞线和HRB400级普通钢筋的后张有粘结部分预应力混凝土T型梁的试验,研究了疲劳荷载下预应力混凝土构件中预应力钢筋和普通钢筋之间应力分配的发展规律。试验结果表明:截面开裂后,疲劳荷载下两种钢筋应力幅值比(Δσp/Δσs)随荷载重复作用次数的增加基本符合“三阶段”的发展规律,其中第二阶段占绝大部分,且在第二阶段中Δσp/Δσs变化幅度较小,基本处于0.6~0.7之间。最后给出一种考虑了粘结性能差异的钢筋疲劳应力增量的计算方法,计算结果和试验结果吻合较好。本文的研究结果对进一步修编、完善我国的混凝土结构设计规范具有一定的参考价值。

Experimental study on stress redistribution of reinforcing steel in prestressed concrete beams under fatigue loading

Accurate calculation on stress range of reinforcing steel is important for fatigue life verification of prestressed concrete members.To study the stress redistribution between prestressed and non-prestressed reinforcement in prestressed concrete versus number of cycles under fatigue loading,tests of 6 post-tensioned bonded PPC T-beams with both prestressed strands and HRB400 ordinary reinforcement have been carried out.The results show that after section cracking,the ratio of stress increment between both steel types(Δσp/Δσs) versus number of cycles basically conforms to the law of three-stages.The second stage occupies the largest part.It also shows that in the second stage,Δσp/Δσsvaries in a small range,basically between 0.6-0.7.Finally,a method considering the different bond behavior of both steel types is proposed for calculating stress increment of reinforcing steel,and the calculation results fit favorably with the experimental results.The corresponding results can be used as a reference to compile the relevant design codes in China.