锈蚀钢筋混凝土T梁的疲劳性能试验

Experimental Study on Fatigue Behavior of Corroded Reinforced Concrete T-shaped Girders

为探明我国早期建造的公路钢筋混凝土T梁桥纵筋锈蚀后的疲劳性能,加工制作10根实际锈蚀率在4.12%~13.72%之间的钢筋混凝土T梁试件,对其开展疲劳应力比在0.25~0.67范围内的疲劳试验。试验结果表明:轻度锈蚀T梁试件的挠度、弯曲裂缝宽度和材料应变均呈现明显的前期快速发展-中期稳定变化-后期迅速增长的“三阶段发展”特征,疲劳破坏一般以弯曲裂缝超限为标志;中度或重度锈蚀T梁试件承受应力比小于0.30左右的疲劳荷载作用时,前者中期平稳发展阶段基本消失,后者甚至会发生低周疲劳破坏;当应力比不超过0.31时,中度和重度锈蚀试件相比轻度锈蚀试件的疲劳寿命分别减小了约48%和71%;当应力比从0.66减小到0.31时,中度和重度锈蚀试件的疲劳寿命分别减小了约85%和90%。由于中度或重度锈蚀的公路钢筋混凝土T梁的实际疲劳寿命远低于200万次的设计疲劳寿命,故设计和运维中应采取措施减小主筋锈蚀率及疲劳应力幅值。

In order to investigate the fatigue performance of corroded RC T-shaped girder bridges early built in China,10 RC T-shaped girder specimens with actual corrosion rates ranging from 4.12%to 13.72%were fabricated,and fa-tigue tests with stress ratios ranging from 0.25 to 0.67 were carried out.The experimental results are as follows.The deflection,bending crack width,and material strain of the lightly corroded specimens exhibit a clear"three-stage de-velopment"characteristic of rapid development in the early stage,stable changes in the middle stage,and rapid growth in the later stage,and its fatigue failure is generally marked by exceeding the limit of bending cracks.When the mod-erately/severely corroded specimens are subjected to fatigue loads with a stress ratio of less than 0.30,the stable de-velopment stage in the middle stage basically disappears,and the latter may even experience low cycle fatigue failure.When the stress ratio does not exceed 0.31,the fatigue life of the moderately/severely corroded specimens is reduced by about 48%and 71%respectively compared to the lightly corroded specimens.When the stress ratio decreased from 0.66 to 0.31,the fatigue life of the moderately/severely corroded specimens decreased by about 85%and 90%,re-spectively.Due to the actual fatigue life of the moderately/severely corroded highway RC T-shaped girders is much lower than the design fatigue life of 2 million times,measures should be taken in the phase of design and maintenance to reduce the corrosion rate of longitudinal bars and fatigue stress amplitude.