Research On Behavior Of Freeze-thaw Damageable Concrete Members Strengthened By CFRP Sheets

CFRP is a multifunctional composite material which is weaved by a certain length ofcarbon fibre. With the rapid development of China’s architecture cause, people put forwardhigher requirements of architecture structure. CFRP sheet possesses a variety of excellentproperties such as high strength, light weight, shock absorption, good mechanical-electriceffect and pressure-sensitive property, saving construction area and a certain delay effect forthe cracking of concrete components and has attracted people’s widespread concern. CFRPsheet strengthening technique has been applied to the engineering practice for a long timeabroad, while is rarely utilized in scientific research and engineering in our country. The paperstudied bond behaviors and load-strain curve of the concrete members strengthened withCFRP sheets, flexural behavior and axially compressive properties of diverse freeze-thawcycling specimens strengthened with CFRP sheets through the methods such asexperimental study, theoretical analysis and ABAQUS finite element simulation. The maincontents are as following:By bending-shear experiment of reinforced beams strengthened with CFRP sheets, usingreinforced specimens strengthened with CFRP sheets of different lengths and layers, the paperstudied damaged type of strengthened end, storey drift, ultimate load and deflection, therelationship between stress and strain. By theoretical analysis, the paper deduced the bondstress formulas of specimens strengthened with CFRP sheets. Simulation experiment wasexecuted by ABAQUS. The paper also made a contrast among the test value, theoretical valueand the simulated values.By freezing and thawing circulation experiment of multiple groups of specimens, thepaper got the mass loss rate and loss rate of dynamic elasticity modulus and built theconstitutive relation model of freezing and thawing circulation after different nbers of freezingand thawing circulation. By totally wrapping and strengthening specimens of different cyclesof freezing and thawing, conducting experiments of flexural behavior, the test acquired risestress-strain curve of totally wrapped and strengthened specimens of different cycles offreezing and thawing. The paper also simulated the strengthened specimens with ABAQUSfinite element software and got bearing capacity and deflection curve. Then the paper made acontrast among the test value, theoretical value and the simulated values and conducted theerror analysis.By axial compression test of reinforced ordinary concrete beams strengthened withCFRP sheets, the paper studied the force performance, reinforcement methods, failure mode,ring direction, vertical deformation and so on. Based on the contrastive analysis of changeparameter such as envelope and subcontracting, the paper revealed that envelope strengthening mode could obviously enhance the bearing capacity of specimens, thuseffectively restrained the circferential deformation of strengthening colns. Based on theexperiment analysis, bearing capacity calculation formula of reinforced beams strengthenedwith CFRP sheets was presented. The whole process force and cracking process of crack weresimulated with ABAQUS, thus obtaining the impact curves that reinforced coln with CFRPsheets load on vertical deformation.After50,100,150freeze-thaw cycles on concrete specimens respectively， thefreeze-thaw specimens were adopted to strengthen with CFRP sheets in an envelope andsubcontracting way. Based on the axial compression tests of reinforced coln, the paper studiedits mechanical behavior, damage modes, reinforcement means, circferential deformation,vertical strain, bearing capacity and circferential strain curve of different locations. The resultsindicated that CFRP sheets strengthening technique can effectively enhance the bearingcapacity of the freeze-thaw specimens and the ring direction and vertical deformation of theenvelope strengthened ones were obvious. The strains of different positions were significantlyaffected by the impact of CFRP sheets. The paper also simulated the force bearing process ofreinforced beams strengthened with CFRP sheets by ABAQUS and obtained the erticaldeformation and load curve of reinforced columns strengthened with CFRP sheets.