Finite Element Analysis And Experimental Study Of Reinforced Concrete Structures With NSM CFRP Strips

Near Surface Mounted(NSM)CFRP(Carbon Fiber Reinforced Polymer)strip reinforcement technology has been widely used in bridge reinforcement because of its advantages such as simple operation,short construction period and almost no influence on the appearance of the original structure.In order to make full use of the material strength of CFRP strips,the reinforcement technology of prestressed NSM CFRP slats has emerged.However,the brittle debonding failure of the reinforced beams using this technology is easy to occur at the concrete cover at the end of CFRP strips,which greatly limits the bearing capacity of the reinforced beams.In order to overcome the above shortcomings and delay the failure of the reinforced beams,research group proposed an improved NSM CFRP strip reinforcement technology,that is,on the basis of the traditional NSM CFRP strip reinforcement technology,added a non-prestressed section at the end.This method can effectively reduce the stiffness difference at the bonding end of prestressed CFRP strips,delay the occurrence of oblique cracks,and improve the flexural performance of the reinforced beams.In order to further explore this technology,based on finite element analysis and experimental research,the following aspects of research are carried out:(1)Based on the previous single shear pull-out test study of research group,a single shear pull-out finite element model considering interface bond-slip relationship was established.The effects of concrete strength,groove width and groove edge distance on the interface bond property were investigated,and the main factors and functional rule affecting the interface bond performance were identified.The results show that the interface between CFRP strip and concrete has better bond performance when using higher strength concrete,smaller groove width and larger groove edge distance.(2)The finite element model of prestressed NSM CFRP strips reinforced RC beams is established on the basis of the bending performance test of the beams,and it is proved that the model can well predict the crack development trend,flexural capacity and failure mode of the reinforced beams.The influence of the level of prestress,the length of bond and the length of unprestressed section at the end on the flexural performance of reinforced beams is analyzed.The results show that when prestressed CFRP strips are used to strengthen RC beams,changing the bonding length of CFRP strips and the length of unprestressed end segment has no obvious influence on the flexural performance of the beams.(3)The fatigue tests of four RC beams reinforced with NSM CFRP strips were carried out.The effects of different bond lengths and whether there is a non-prestressed section at the end on the fatigue performance of reinforced beams are discussed.By using Fe-Safe finite element software,the fatigue life of the reinforced beam is predicted under the influence of different bond length and the length of the non-prestressed section at the end.It is found that the failure mode and fatigue life of the reinforced beam can be changed to some extent by changing the bond length and the end length of the non-prestressed section.