嵌入式FRP抗剪增强梁斜裂缝水平投影长度计算

为计算嵌入式FRP抗剪增强梁在四点加载作用下的斜裂缝水平投影长度,利用投影长度经验公式和变角空间桁架模型分别研究了剪跨比和纵筋-箍筋强度比对投影长度的影响,在此基础上综合考虑两者的相互关系,同时根据9根FRP嵌入式增强梁的实测试验数据,采用最小二乘法拟合斜裂缝投影长度计算公式.分析结果表明,单独考虑剪跨比和纵筋-箍筋强度比都不能很好地预测斜裂缝水平投影长度,而将两者结合能够较好地反应斜裂缝出现和发展的全过程,从而准确地计算斜裂缝水平投影长度.推导公式的计算结果和试验实测值取得了很好的吻合,误差小,离散程度低,同时还表明剪跨比是影响斜裂缝投影长度的主导因素.

Calculation of horizontal proljection length of diagonal cracks in near-surface mounted FRP shear strengthened beams

To calculate horizontal projection length of diagonal cracks in near-surface mounted(NSM) FRP(fiber reinforced polymer) shear strengthened RC(reinforced concrete) beams under four-points loading,the empirical formulae and variable-angle space truss model were adopted respectively to investigate the influence factors that control the horizontal projection length.Based on this,two major influence factors,shear-span ratio and strength ratio of longitudinal steels to stirrups,were integrated and the formula was derived through fitting test datum of nine NSM FRP shear strengthened beams by means of least square method.Study results indicate that the horizontal projection length of diagonal cracks cannot be predicted accurately when considering shear span ratio and strength ratio of longitudinal steels to stirrups separately.However the horizontal projection length can be well predicted through integrating these two influence factors due to their well representation of the entire process of diagonal cracks' occurring and development.As a result accurate computing results are verified through comparing with the test datum,while the formulae also indicates that shear span ratio is the major influence factor of horizontal projection length.