考虑CFRP布剥离的无腹筋RC梁剪切尺寸效应分析

Shear size effect of RC beam without web reinforcement considering debonding of CFRP sheets

为分析考虑CFRP布剥离的无腹筋RC梁剪切尺寸效应,建立了考虑混凝土材料非均质性、钢筋与混凝土间的黏结性能以及CFRP布与混凝土相互作用关系的CFRP加固无腹筋钢筋混凝土(RC)梁三维细观数值分析模型。在验证细观数值分析模型合理性的基础上,设计并建立28根CFRP布加固RC梁模型,分析不同配纤率(0.0555%、0.1110%和0.2220%)和不同截面尺寸(80 mm×200 mm、160 mm×400 mm、240 mm×600 mm和320 mm×800 mm)情况下,CFRP布剥离对RC梁剪切破坏及其尺寸效应的影响。分析结果表明:考虑CFRP布剥离能够真实反映CFRP布与混凝土非可靠黏结状态下RC梁的实际剪切性能;梁名义抗剪强度随截面尺寸增大而降低,均表现出明显的尺寸效应现象。当加固梁截面高度从200 mm增加到800 mm时,3组配纤率对应的考虑剥离的RC梁的名义抗剪强度分别下降了26.5%、17.8%和13.1%,而未考虑剥离的RC梁的名义抗剪强度分别下降了20.6%、13.0%和8.1%。考虑CFRP布剥离时,CFRP布对RC梁剪切尺寸效应削弱效果不显著。依据数值分析结果,提出了考虑CFRP布剥离的CFRP加固无腹筋RC梁抗剪强度尺寸效应律。考虑CFRP布剥离得到的理论值与试验值吻合较好,验证了扩展尺寸效应律的合理性和准确性,在实际模拟中应考虑CFRP布的剥离。

In order to analyze the shear size effect of RC beams without web reinforcement considering debonding of CFRP sheets,a three-dimensional(3D)meso-scale numerical analysis model of CFRP-strengthened reinforced concrete(RC)beams without web reinforcement was established,which considers the heterogeneity of concrete,the bond-slip relationship between reinforcement and concrete,and the interaction between CFRP sheets and concrete.On the basis of verifying the rationality of the numerical method,meso-scale models of 28 CFRP-strengthened RC beams were designed and established.The effects of the debonding behavior of CFRP sheets on the shear failure behavior and size effect of RC beams under different CFRP fiber ratios(0.0555%,0.1110%,0.2220%)and different cross-section sizes(80 mm×200 mm,160 mm×400 mm,240 mm×600 mm and 320 mm×800 mm)were analyzed.The analysis results show that considering the debonding of CFRP sheets can truly reflect the actual shear performance of RC beams in the state of imperfect bonding between CFRP sheets and concrete.The nominal shear strength of the strengthened beams decreases with the section size,showing an obvious size effect phenomenon.For the three groups of fiber ratios,when the height of the RC beam is increased from 200 mm to 800 mm,the nominal shear strength of the RC beams which consider CFRP sheet debonding decreases by 26.5%,17.8%and 13.1%,respectively,while those not considering CFRP sheet debonding decreases by 20.6%,13.0%and 8.1%,respectively.When considering the debonding behavior of CFRP sheets,the weakening effect of CFRP sheets on the shear size effect of RC beams is not significant.Based on the numerical test results in this paper,a size effect law of shear strength of CFRP-strengthened RC beams without web bars considering the debonding of CFRP sheets was proposed.The theoretical values obtained by considering the debonding of CFRP sheet are in better agreement with the test values,which on the one hand verifies the rationality and accuracy of the extended size effect law,and on the other hand indicates that the debonding of CFRP sheet should be considered in the practical simulation.