盐溶液干湿交替作用下FRP加固梁长期挠度研究

Study on the long-term deflection of FRP-strengthened RC beams subjected to sustained loads and wetting-drying cycles

通过5根试件研究盐溶液干湿交替作用下纤维增强聚合物(FRP)加固钢筋混凝土梁的长期变形性能,持载水平为未加固梁极限荷载的30%或60%,FRP种类考虑CFRP和GFRP,盐溶液干湿交替天数为360 d,分析不同持载水平、FRP种类对加固梁长期挠度、裂缝宽度等影响规律。试验结果表明:加固梁前期挠度增长较快,后期趋于稳定;其长期挠度随荷载水平的增加而增大;CFRP加固梁长期挠度小于GFRP加固梁;持载水平为60%极限荷载的CFRP加固梁裂缝宽度总体小于GFRP加固梁;基于试验结果,考虑盐溶液干湿交替作用对FRP材料性能的影响,给出了FRP加固混凝土梁长期挠度计算方法,其计算值与试验值吻合较好。

Five reinforced concrete(RC)beams strengthened with fiber-reinforced polymer(FRP)sheets were subjected to wetting-drying cycles and a sustained load(for 360 days at load levels of 30%,and 60%of the ultimate loading capacity of the un-strengthened beam and the types of FRP consisted of CFRP and GFRP).An experimental study was designed to investigate the impacts of different loading levels and the types of FRP on the long-term deflections of strengthened RC beams and the crack width.The test results showed that the deflection of the FRP-strengthened RC beams increased rapidly at the early stage and tended to be stable at the later stage.The long-term deflections of the FRP-strengthened RC beams increased with the increase in load levels.The long-term deflections of CFRP is smaller than that of GFRP.The crack width of the 60%ultimate loading CFRP is generally smaller than that of the GFRP.Based on the test results and considering the effect of the wetting-drying cycles on the properties of FRP,a calculation model for the long-term deflection of FRP-strengthened RC beams is given,and the calculated values are in good agreement with the experimental values.