Numerical And Experimental Study On The Bond Performance Of FSCB-concrete

Corrosion of steel bars is one of the most common durability problems of reinforced concrete structures in coastal areas.This problem can be solved by using FRP bars with high tensile strength and strong corrosion resistance in Marine environment instead of stressed steel bars.However,the commonly used GFRP bars have fatal shortcomings such as low stiffness and brittle failure,which seriously harm the structural safety.Comprehensive analysis of the use of reinforcement in concrete structures and the advantages and disadvantages of FRP reinforcement,in this paper,the advantage of the two are combined,is a new type of Composite reinforcement material: GFRP-Steel Composite reinforcement（Glass Fiber Reinforced Polymer-Steel Composite Bar,outer package GFRP Fiber,for Steel inner core,hereinafter referred to as FSCB）for the preparation of novel FSCB concrete structure,and study of FSCB-concrete bonding performance.In this paper,the effects of concrete strength,fiber thickness of FSCB cross section and stirrup constraint on the bond performance between FSCB and concrete are discussed by means of experimental and numerical analysis.The bondslip constitutive model of FSCB-concrete interface is established,and the finite element simulation of bending resistance of FSCB-steel concrete beams is carried out based on this model.The main research contents and conclusions of this paper are as follows:（1）Through the tensile mechanics experiment,the failure mode of the outer fiber thickness of 2/4/6mm FSCB was observed,and the mechanical parameters such as stiffness and strength of the FSCB were obtained.Based on the material composite rule,the tensile constitutive model of FSCB was established,and the predicted values of the theoretical model were compared with the experimental data,which were in good agreement.（2）The design and implementation of the center for FSCB drawing experiment,observed the failure modes of the bonding interface,this paper analyzed the concrete strength,FSCB section fiber thickness and stirrup restraint on FSCB and the influence of the concrete bonding properties,the results show that the ultimate bond strength and its corresponding FSCB and concrete load side slip value increased with the increase of tensile strength of concrete;On the contrary,with the increase of the fiber thickness of FSCB cross section,both decrease.The effect of stirrup constraint on the ultimate bond strength is only obvious when the thickness of the protective layer is less than 5d.（3）Using ABAQUS and based on the three dimensional finite element method,considering the FSCB and concrete bonding-slip behavior between established FSCB center drawing experiment with concrete finite element model,the section of fiber thickness and strength of concrete,FSCB stirrup restraint factors such as the finite element calculation results and the experimental results of comparative analysis,verify the validity of the model.Through the finite element calculation results can be observed at different stress stages,FSCB and concrete bonding interface and the stress distribution state of tensile damage degree,the results show that the closer the load side,the greater the stress of the bonding interface,the more concentrated the distribution,and the more serious damage degree,further verified the proposed FSCB and the accuracy of the concrete bonding-slip constitutive model.（4）Considering the bond-slip behavior between FSCB and concrete,a finite element model of the flexural strength of FSCB-SRC beams is established,and the influence of the fiber thickness of FSCB section on the flexural strength of FSCB-SRC beams is discussed and analyzed.The results show that with the increase of the fiber thickness of FSCB section,the ultimate flexural strength of FSCB-SRC beams increases.FSCB-SRC beams still have a large space to increase the bearing capacity after the yielding of the inner core steel bars.Compared with the traditional steel bars/pure FRP bars,FSCB-SRC beams have obvious advantages and are more in line with the safety concept of structural design.