FRP筋混凝土梁的抗剪承载力

Shear bearing capacity for concrete beams with FRP reinforcement

利用《纤维增强复合材料建设工程应用技术规范》(GB 50608-2010)建议的纤维增强复合(fiber-reinforced polymer,FRP)筋混凝土梁受剪承载力计算公式,分析了收集到的171根FRP筋试验梁(包括无箍筋梁和配FRP箍筋梁)的抗剪承载力.对比了各梁抗剪承载力的计算值与试验值发现,《规范》推荐的方法过于保守.为此,采用灰度关联法分析了影响FRP筋试验梁受剪承载力的主要因素.结果表明,截面有效高度对受剪承载力影响最大,其次分别为纵筋配筋率、混凝土抗压强度和剪跨比.据此分析了《规范》公式存在对截面有效高度估计不足、未考虑剪跨比影响等缺陷,并在此基础上对《规范》公式进行了相应修正.利用上述171根梁的试验数据验证了修正后的抗剪承载力计算公式的合理性.结果表明:对于无箍筋梁,修正前后试验值与理论值之比的均值由4.78变为1.49;而配FRP箍筋梁的均值则由2.18变为1.40.

171 test beams reinforced with fiber-reinforced polymer(FRP) bars including with and without FRP stirrups were analyzed by using shear bearing capacity’s formulas recommended by the Technical Code for Infrastructure Application of FRP Composites(GB 50608-2010).By comparing each beam’s predicted shear strength with its corresponding experimental value,the result showed that the method adopted by the Code was highly conservative.Therefore,main factors affecting the shear capacity of FRP reinforced concrete members with shear reinforcement were analyzed by adopting the grey relational analysis.The results showed that the most important factor was effective depth of the cross section,followed by longitudinal reinforcement ratio,concrete compressive strength,the shear span ratio and so on.Accordingly,it was analyzed that the formulas in the Code underestimated the effect of effective depth of the cross section and ignored its impact on shear span ratio and so on.The formulas were revised on the basis of previous analyses and their rationality verified by using aforementioned 171 beams test data.Compared with the unrevised provision,the mean of ratio of the test to the predicted shear strength of the beams without shear reinforcement went from 4.78 down to 1.49,whereas in the case of those beams with stirrups the figure went from 2.18 down to 1.40.