碳纤维薄板增强RC梁的弯曲疲劳寿命

纤维增强复合材料(FRP)加固钢筋混凝土(RC)梁的疲劳行为是国内外土木工程界的前沿课题.文中将18根尺寸为1850mm×100mm×200mm的碳纤维薄板(CFL)增强RC梁分为4组进行弯曲疲劳实验,探讨其疲劳性能.通过理论分析及对上述疲劳实验数据的分析和讨论,按照所提出的CFL增强梁的容许疲劳寿命和极限疲劳寿命的新概念,得到了相应的两类S-N和P-S-N曲线,发现CFL增强梁的容许疲劳寿命和极限疲劳寿命分别是其静载极限强度的65%和67%;推导了增强梁的跨中最大挠度与载荷循环数、单根梁的疲劳寿命及应力水平之间的关系式,在此基础上,提出了一种只需少量循环加载(研究中建议取n=100 ～1000)的非破坏性弯曲疲劳试验数据就能预测该增强梁疲劳寿命的新方法.最后通过另外3根CFL增强梁的疲劳试验对所提出的寿命预测方法进行了验证.

Fatigue Lives of RC Beams Strengthened with Carbon Fiber Laminates Under Bending Loads

The fatigue behavior of RC ( Reinforced Concrete) beams strengthened with FRP ( Fiber Reinforced Polymer ) is an important subject in civil engineering in the world. In this paper, 18 RC beams (1 850mm × 100 mm × 200 mm) strengthened with CFLs (Carbon Fiber Laminates) are divided into 4 groups and are tested to investigate their fatigue behaviors under bending loads. Based on the data of fatigue test and theoretical analyses, S-N and P-S-N curves of the RC beams strengthened with CFLs are obtained according to the new conceptions of permissive and extreme fatigue lives, finding that the ratios of the permissive and extreme fatigue strength to the ultimate static strength are respectively 65% and 67%. The relationships among the mid-span deflection, the loading cycle number, the individual fatigue life and the stress level are then deduced and validated. Afterwards, a new method that only needs some nondestructive experimental data of fatigue (the fatigue load cycles n recommended here is 100 ～ 1000) is proposed to predict the individual fatigue life. The proposed prediction method is finally validated by the fatigue tests of another three RC beams strengthened with CFLs.