Study On Flexural Performance Of HB-FRP Reinforced Normal And Rusted RC Beams

Externally bonding fiber reinforced polymers(EB-FRP)is widely used in today’s engineering reinforcement field due to the advantages of easy construction,good corrosion resistance and high strength,but in the process of service,due to the development of cracks in the structure and the environmental impact,the FRP will be peeled off prematurely and cannot give full play to its effect on the structure.However,due to the development of structural cracks and environmental influences during service,FRP can be peeled off prematurely and its reinforcement effect cannot be fully utilized.Among them,Hybrid bonded fiber reinforced polymers(HB-FRP)can inhibit the development of FRP peeling by applying additional friction and pinning action to FRP with anchors,which can significantly improve the utilization rate of FRP.The utilization rate of FRP is greatly improved,and thus the load-bearing capacity of the reinforced members is enhanced.Although there have been a considerable number of research results on HB-FRP strengthening technology,the influence law of different anchorage parameters on the flexural performance of HB-FRP strengthened ordinary RC beams(Reinforced concrete,referred to as RC beams)is not yet comprehensive,and a complete strengthening design method has not been formed.In addition,the reinforcement effect of HB-FRP reinforcement technology on rusted RC beams and the inhibition of weak interface separation by anchorages are not clear,which limits its application in coastal corrosive environment.Therefore,this paper carries out a study on the flexural performance of HBFRP reinforced common and rusted RC beams under different anchorage parameters to provide theoretical support and design basis for its application in practical engineering.The main research contents of this paper are as follows.(1)The flexural performance tests of HB-FRP reinforced ordinary RC beams with different bolt torque,fastener spacing,FRP bonding pattern and anchorage distribution are designed,and the effect law of different anchorage parameters on the flexural performance of reinforced beams is analyzed by the test results.The results show that the increase of bolt torque enhances the flexural performance of reinforced beams;the increase of fastener spacing decreases the flexural performance of reinforced beams when the damage mode is FRP peeling;the pinning action of bolts substantially increases the ultimate load and FRP utilization rate of reinforced beams,but leads to the brittle damage of anchorages;under the same total anchorage action,the enhancement of mid-span anchorage action improves the In the case of the same total anchorage action,the enhancement of the mid-span anchorage action improves the flexural stiffness of the strengthened beam,and the enhancement of the end anchorage action improves the ductility of the strengthened beam.(2)A three-dimensional finite element model of the HB-FRP reinforced RC beam was established,and extended simulations were carried out to calculate the bolt torque,fastener spacing,fastener width and FRP width.The results show that the calculated results of the established HB-FRP reinforced RC beam model are in good agreement with the experimental results;the calculated ultimate load and residual load increase linearly with the decrease of fastener spacing,and the increase of bolt torque,fastener width and FRP width improves the ultimate load and residual load,but may lead to the early crushing of the concrete in the compression zone of the reinforced beam;the FRP width is too large to reduce the utilization rate of FRP,and FRP is not easy to be peeled.(3)The inhibitory effect of fasteners on the ordinary bonding area of FRP was analyzed,and the calculation model of the interfacial chemical bonding of HB-FRP reinforcement system considering the effect of fastener spacing was established,and the effect of FRP interfacial slip on the prediction accuracy of the bearing capacity was analyzed.The results show that: the fasteners increase the bonding area of FRP in the ultimate state;the calculated value of interfacial chemical bonding force agrees well with the test value,and the corresponding prediction accuracy of flexural bearing capacity is better than the previous model;the FRP slip strain will be generated after the FRP interfacial slip occurs,and the calculation accuracy of bearing capacity decreases as the slip strain increases.(4)To address the problem that the double interface(FRP-concrete interface and protective layer interface)in FRP-reinforced corroded RC beams is prone to peeling,tests on the flexural performance of HB-FRP-reinforced corroded RC beams with different fastener spacing and anchorage depth were carried out to investigate the inhibitory effects of fastener spacing and anchorage depth on the peeling of the double interface.The results showed that the cracking of the protective layer deteriorated the load carrying capacity of the rusted RC beams reinforced with HB-FRP compared with the uncorroded reinforced beams with the same anchorage parameters;the anchorage depth and fastener spacing had no significant effect on the cracking load of the protective layer;the anchorages at the corresponding locations failed after the protective layer peeling.(5)The calculation model of cantilever beam of rusted RC beam reinforced by HBFRP was established,and the FRP stress corresponding to the cracking of protective layer was obtained,and the corresponding cracking load was projected,and the calculation method of flexural load capacity of reinforced beam based on the number of anchor failures was proposed.