CFRP布斜贴加固无腹筋RC梁受剪性能及尺寸效应试验研究

Experimental study on shear performance and corresponding size effect of RC beam without web reinforcement strengthened by oblique CFRP sheets

为研究CFRP布斜贴加固无腹筋RC梁的受剪性能及尺寸效应,以剪跨比λ(λ为1.0、1.5、2.0)和截面尺寸(梁高为300.600、900mm)为主要研究变量,设计9根CFRP布斜贴(粘贴角度为45°,配纤率为0.0835%)加固无腹筋钢筋混凝土(RC)梁,基于四点弯曲加载试验,分析破坏模式、裂缝扩展行为、CFRP布应变、峰值荷载和跨中挠度等随剪跨比和截面尺寸的变化规律。研究结果表明:在试验剪跨比范围内,梁最终破坏模式均为剪切破坏;剪跨比从1.0增至2.0,梁的承载力降幅为45%~51%,CFRP布对受剪承载力贡献增幅为23%~28%,梁的截面抗剪强度降幅为46%~51%;剪跨比对梁截面抗剪强度下降趋势影响较小。基于试验结果,提出CFRP斜贴加固无腹筋RC梁尺寸效应律,适用于考虑剪跨比对CFRP布加固RC梁受剪性能的影响。

In this paper,nine webless reinforced concrete(RC)beams strengthened by oblique CFRP sheets(adhesion angle of 45°,CFRP ratio of 0.0835%)with shear-span ratios(λ was 1.0,1.5,2.0)and cross-section sizes(beam heights of 300,600,900 mm)as the main study variables were designed and tested to investigate their shear performance.We concentrated on the examination of the variation rules of damage mode,crack extension behaviour,CFRP fabric strain,peak load,and mid-span deflection with the shear-span ratio and cross-section size based on the four-point bending loading test.The findings indicate that:the final damage mode of the beam is shear damage within the test shear-span ratio range;with the shear-span ratio increases from 1.0 to 2.0,the load carrying capacity of the beam decreases from 45%to 51%,the contribution of CFRP fabric to the shear load carrying capacity accounts for an increase of 23%to 28%,and the nominal shear strength of the beam's cross-section decreases from 46%to 51%;the shear-span ratio has a relatively small effect on the trend of the beam's cross-section shear strength as it decreases.The size effect law for webless RC beams strengthened by oblique CFRP sheets was provided based on the test data presented in this study.It can be applicable to the investigation of how the shear-span ratio affects the shear performance of RC beams strengthened by CFRP sheets.