Research On Flexural And Shear Resistance Of Reinforced Concrete Beams Strengthened With FRP Composites

The externally bonded fiber-reinforced polymer(EB-FRP)has been one of the most popular techniques and widely used in the retrofitting,strengthening,repair of concrete structures due to its remarkable mechanical properties.The premature debonding of FRP-concrete interface,which is a sudden and catastrophic failure of the FRP strengthened concrete structure,leads to a very low effective utilization ratio of FRP material and an poor ductility.Much effort has been made in the research community to improve the bond strength and solve the above mentioned problem,hybrid-bonded FRP(HB-FRP)combined with special mechanical fasteners and adhesive bonding FRP enhance the interfacial bond strength distinctly and enormously.In this paper,The HB-FRP mechanical fasteners and end-anchorage devices has been developed and installed to strengthen the test beams.Then HB-FRP strengthened reinforced concrete beams were tested under four-point bending to verify the flexure and shear behavior.This proposed research,by controlling and Changing the corresponding test variables,aims to significantly restrain the premature debonding of FRP,increase the strength utilization ratio and finally develop a design methodology for the Strength and ducility of hybrid-bonded FRP strengthened reinforced beams.Finally,predicton models for the ultimate flexural and shear strength model under the HB-FRP mechanical fasteners and end-anchorage devices was proposed refer to existing interfacial bond strength and ultimate flexural and shear strength models.Comparisons with the experimental results indicate that the proposed model can provide a reasonable good accuracy in predictions.The experimental studies on the flexural performance of hybrid bonded FRP strengthened RC beams has adopted a surface preparation called mechanical abrading and reasonably arranged HB-FRP mechanical fasteners and end-anchorage devices.This test has selected the applied torque as the variable of HB-FRP system and selected the width of deformation section as the variable of end-anchorage devices.The ultimate flexural strength,displacement ductility,failure mode,cracks distribution,FRP strain distribution and interfacial shear stress and the effect of test variables were examined.It has demonstrated that HB-FRP system and end-anchorage devices could significantly improve the flexural ultimate strength and ductility,effectively prevent premature debonding of FRP and increase strength ultization ratio of FRP,and enhance the interfacial bond capacity.The experimental studies on the shear performance of hybrid bonded FRP strengthened RC beams has adopted a surface preparation called mechanical abrading and reasonably arranged HB-FRP system to fasten the U-shaped FRP wraps.This test has selected the applied torque as the variable of HB-FRP system and selected the width of deformation section as the variable of end-anchorage devices.The ultimate shear strength,displacement ductility,failure mode,cracks distribution,FRP strain distribution and the effect of test variables were examined.It has demonstrated that HB-FRP system could significantly improve the flexural ultimate strength and ductility,effectively retrain premature debonding of FRP and increase strength ultization ratio of FRP.Predicton models for the ultimate flexural and shear strength model under the HB-FRP mechanical fasteners and end-anchorage devices was proposed refer to existing interfacial bond strength and ultimate flexural and shear strength models.Comparisons with the experimental results indicate that entirely prediction results are a bit smaller than experimental values and the proposed model can provide a reasonable security and good accuracy in the practical design.