Experimental study on strain distribution in externally bonded FRP for shear strengthening of RC beams

Abstract

外贴纤维复合材料可以提高混凝土梁斜截面抗剪承载力。对外贴封闭纤维箍加固构件,其破坏过程经历了从梁侧纤维剥离到最终纤维拉断两个状态。显然,从适用性的角度,梁侧纤维剥离状态也是一个重要的状态,但是,目前该领域的研究都集中在最后的纤维拉断状态。本文通过外贴封闭纤维箍加固梁的试验研究,重点研究了梁侧纤维剥离之前,斜截面纤维应变发展及分布的规律。试验表明,梁侧纤维的剥离破坏和纤维拉断破坏首先产生在其中一条纤维箍上,然后沿着斜裂缝其它纤维箍相继产生。在斜裂缝上,纤维应变的分布是极不均匀的。斜截面纤维应变分布系数,即沿斜裂缝上纤维应变的平均值除以相应条件下斜裂缝上纤维应变的最大值,与纤维配置量的关系不大,但随着荷载水平的增大而缓慢增加,它的主要影响因素是剪跨比。本文在试验分析的基础上,提出了纤维加固梁斜截面纤维应变分布系数的初步计算模式。 The strain distribution in the externally bonded FRP for shear strengthening RC beams is studied in the paper. Twelve pieces of simply supported RC beams with externally bonded FRP are tested. It is stressed on the development and distribution of strains in externally bonded FRP before debonding. It is found that the both debonding and FRP rupture occurred in the most critically stressed FRP strip first, and then spread across the shear crack. Along the shear crack, the strain distribution of FRP is found with strong non-uniform. At last, a simply approach to predict the strain distribution coefficient of FRP is proposed in the paper.