Study On The Shear Performance Of Rc Beams Strengthened By Hybrid Bonding FRP

Hybrid bonding FRP is a hybrid strengthening method combining externally bonding FRP with steel plate mechanical fastening.After the relevant researches at home and abroad,the mechanical anchor system has been developed into the adhesive anchor-steel sheet-fastening.Hybrid bonding FRP has been proved to be a good flexural strengthening effect on the concrete member.It can improve the interfacial bonding property of FRP-concrete and develop the flexural capacity of the reinforced concrete beams tremendously.The present study focuses on the interfacial bonding property of hybrid bonding FRP and the interfacial shear failure mechanism.The present study uses hybrid bonding FRP to shear strengthen the inclined section of the reinforced concrete T-beam,and researches the shearing performance of the inclined section of the reinforced concrete T-beam after strengthening and the shearing contribution of HB-FRP.The present study designed eight self-anchored in-plane Iosipescu shear tests for hybrid bonding FRP.Considering the influence of different paste lengths and paste layers of FRP on the interfacial bonding property and based on the development law of the interfacial shear stress of FRP-concrete,the present study divided the process from the initial force to the final destruction of the FRP in hybrid bonding FRP into three stages.It's shown that the steel sheet-fastenings in hybrid bonding FRP control the continual debonding of FRP and increase the FRP-concrete interfacial bonding strength by 18.02%.Besides,the steel sheet-fastenings make the failure mode change from FRP debonding failure to FRP fracture failure,which improves the rate of utilization of the strength of FRP tremendously.The failure of hybrid bonding FRP is commonly influenced by the ultimate tensile strength of the materials and the strength of the steel sheet-fastenings,and it's shown that the strength of single steel sheet-fastening can be 14.523kN.It's proposed that the reasonable space between steel sheet-fastenings should be 0.6Le?1.0Le.The present study had shear capacity tests on the inclined sections of the reinforced concrete T-beams strengthening with hybrid bonding FRP.It compared the shear capacity of the inclined sections of the T-beams strengthening with HB-FRP with those strengthening with EB-FRP.It also studied the failure mode,shear capacity,deflection deformation of the T-beams,the development and distribution of the inclined cracks in the reinforced concrete and the strain of FRP and the stirrups etc.The shear capacity of the T-beams strengthening with hybrid bonding FRP under the secondary load was also discussed in this thesis.It's shown that the deflection deformation of the reinforced concrete T-beams strengthening with HB-FRP is small and the shear capacity of the inclined section increases by 23.6%-25.5%,which comparing with the shear capacity of the inclined section strengthening with EB-FRP increases by 7.2%-9.1%.It means that hybrid bonding FRP can improve the stress capacity of the reinforced concrete T-beams and control the inclined cracks developing in the reinforced concrete remarkably.The average rate of utilization of strength of FRP is 2.62 times higher than the rate of EB-FRP.This study deduces the design formulas for the shear capacity of the inclined section of the reinforced concrete T-beams strengthening with hybrid bonding FRP based on the data analysis and the finite element entity model analysis in this thesis,and proposes calculation method for the shearing contribution of HB-FRP,in which the lower limiting value of the shearing contribution is calculated as the value of FRP debonding control,while the upper limiting value of the shearing contribution is calculated as the value of FRP fracture control.It's shown that the actual value of the shearing contribution of HB-FRP is between the upper limiting value and the lower limiting value.With the finite element entity model analysis,the parametric analysis for T-beams strengthening with the different spaces between FRP sheets and the different spaces between steel sheet-fastenings will be shown in this paper.The present study revises the maximal strain limiting value ?max to 12145?? for the failure mode in which it's easy to happen the situation that the FRP doesn't fracture,while the reinforced concrete fractures in the structure member strengthening with HB-FRP on its vertical side.This paper also analyzes the value of tension failure of the adhesive anchor in the steel sheet-fastenings and proposes the torque value of the bolt pretightening force should not exceed 13 N·m.