Experimental Study On The Bonding Properties Of Steel-carbon Fiber Composite Bars With All-coral Concrete

In the construction of offshore island projects,using coral debris as coarse and fine aggregate and mixing with seawater to prepare all-coral concrete can achieve the purpose of using local materials,saving costs and shortening the construction period.But the problem of reinforcement corrosion caused by the large amount of chloride ions in coral aggregate and mixing seawater and the hot and humid Marine environment is the main obstacle to the application of coral concrete.While the adoption of high strength,light weight,corrosion resistance and other characteristics of FRP bars can effectively solve the problem of steel corrosion,but because of the FRP bars brittle,low elastic modulus,high price characteristics,easy to make the structure deflection deformation,brittle damage,resulting in its application in engineering is difficult to get a wide range of promotion.Therefore,Steel-carbon fiber composite Bar(SCFCB)with high elastic modulus,good ductility,corrosion resistance and high ultimate strength can be used to replace Steel reinforcement and FRP reinforcement,which can well solve the durability problem caused by Steel corrosion and brittle failure problem caused by low elastic modulus of FRP reinforcement.Since the bonding property between SCFCB and coral concrete is one of the basic mechanical behaviors of SCFCB coral concrete structure,the lack of research on this mechanical behavior seriously affects the calculation and performance analysis of SCFCB coral concrete structure.In this paper,the bonding performance of SCFCB and all-coral concrete under different test methods,the factors affecting the bonding strength,and the variation law of the bond stress distribution along the buried length of SCFCB were studied and analyzed through fiber Bragg grating sensing technology.The main contents and research results of this paper are as follows:1.Through the central drawing test,the bond performance between SCFCB and whole coral concrete was studied,including the bond failure form and mechanism analysis,as well as the factors affecting the bond performance.The research results show that SCFCB and coral concrete bonding failure stress process,the bond-slip curve,the bond mechanism,failure pattern and FRP reinforcement-ordinary concrete,the FRP tendons-coral concrete is relatively close,the factors,the bond length,coral,concrete strength,aggregate characteristics,SCFCB diameter and surface condition on bonding performance and greater influence on the failure pattern,and SCFCB and coral concrete performance is better than that of pure CFRP reinforcement.2.The bond slip curve characteristics,failure modes and mechanism of scfcb-coral concrete with different diameters were studied through beam test,and compared with the central drawing test.The results show that the bond slip curve of the beam specimen is similar to that of the central specimen,but the average bond stress is lower than that of the central specimen.The effect of stirrups on the bond properties of left and right beam composite bars is not obvious.3.The variation law of the bond stress distribution along the buried length of SCFCB was studied and analyzed.At the initial stage of the test,the peak of the bond stress within the buried length was mainly concentrated near the loading end,while the bond stress near the free end was small.With the increase of the load,the peak value of the bond stress gradually drifts to the free end,and the bond stress curve is convex,high in the middle and evenly distributed on both sides.