Finite Element Analysis Of Shear Performance Of Concrete Beams With GFRP-Steel Composite Stirrup

GFRP-steel composite reinforcement(that is,the inner core is steel bar and the outer layer is wrapped with GFRP material)can effectively improve the poor corrosion resistance of steel bars,and can make up for the defects of low stiffness and insufficient ductility of GFRP bars.Therefore,it has been widely studied by scholars.At present,the shear performance of GFRP-steel composite stirrup concrete beams has not formed a perfect and unified shear theory,and there is still a lack of shear analysis considering the influence of various factors.In order to ensure the rationality of GFRP-steel composite bars applied to the shear design of concrete beams,this paper conducts a parametric analysis of the shear performance of GFRP-steel composite stirrup concrete beams through numerical analysis,and establishes a practical calculation formula for shear capacity and oblique crack width.The main research contents are as follows:(1)The finite element model of GFRP-steel composite stirrup concrete beam is established.The validity of the finite element model is verified by comparing with the experimental results.By changing the four parameters of shear span ratio,tensile longitudinal reinforcement ratio,stirrup inclination angle and GFRP/steel thickness ratio,the parametric analysis of GFRP-steel composite stirrup concrete beams was carried out,and the influence of each parameter on the cracking load,ultimate load and corresponding mid-span deflection of component beams was obtained.(2)Based on the calculation formula of shear capacity of beams without stirrups in GB50010-2010,combined with the results of parameter analysis of beam bearing capacity,the corresponding fitting analysis of the data is carried out,and the reasonable shear span ratio correction coefficient,longitudinal reinforcement ratio correction coefficient and stirrup inclination angle correction coefficient are obtained respectively.The calculation formula of shear capacity of GFRP-steel composite stirrup concrete beams which can reflect the influence of shear span ratio,tensile longitudinal reinforcement ratio and stirrup inclination angle is established.By comparison,the theoretical calculation value of the formula is in good agreement with the experimental measured value.(3)Considering the crack width limits of Chinese and American codes and relevant scholars on the design of FRP reinforced concrete structures,this paper suggests that the maximum crack width limit of GFRP-steel composite stirrup concrete beams is 0.5mm;based on the finite element analysis results,a practical formula for calculating the diagonal crack width of GFRP-steel composite stirrup concrete beams under load is derived.By comparing with the experimental results,the crack width calculated by the formula is in good agreement with the measured values,which indicates that the formula can accurately predict the development of diagonal cracks under shear failure of GFRP-steel composite stirrup concrete beams.