FRP加固混凝土梁中弯曲和弯剪裂缝引起的FRP剥离破坏试验

采用同样尺寸的钢梁和混凝土梁,通过中间绞结和底面粘贴FRP布而形成的组合梁,对其进行抗弯试验来研究钢筋混凝土梁弯曲或弯剪裂缝所导致的FRP剥离破坏.试验共设计了7组21根组合梁,通过2个对称的集中荷载进行抗弯试验,重点研究了组合梁破坏过程和形态、FRP布在加载过程中应变分布的规律、不同的裂缝开展程度对组合梁初裂荷载和极限承载能力的影响以及混凝土强度对FRP与混凝土粘结强度的影响.试验结果表明:组合梁的初裂荷载与FRP的长度没有关系,主要取决于裂缝的竖向位移;裂缝的竖向位移和FRP的长度对梁的极限荷载具有较大的影响,特别是在FRP锚固长度较小的情况下.针对梁中弯曲及弯剪裂缝引起的FRP剥离破坏进行了深入的试验研究,为工程结构加固提供了一定的参考依据.

Experimental investigation on flexural and flexural/shear crack induced debonding failure in FRP strengthened concrete beams

The combined beam consisting of a concrete block and a metal fixture,which were jointed by a steel hinge at the upper side of the two parts and bonded with a FRP(fiber reinforced plastic) plate on the bottom surface,was tested in flexure to study the debonding behavior induced by a major flexural or flexural/shear crack.In the experimental program,21 beams of 7 series were loaded in four-point bending to investigate the failure mechanism,the strain distributions of the FRP plate under different load values,the effect of crack size on the initial debonding load and the ultimate load,and the effect of concrete strength on the bond capacity between FRP and the concrete.According to the test results,the length of the FRP plate shows little effect on the initial debonding load and it is significantly affected by the vertical displacement of the crack. The ultimate load of the beam is greatly affected by the vertical displacement of the crack and the length of the FRP plate,especially when the FRP plate is relatively short.The FRP debonding behavior induced by flexural or flexural/shear crack is comprehensively investigated.