Experimental Research On Durability Of FRP Confined Load-bearing Short Columns

Nowadays, extensive research interests have been attracted to the innovative,reliable, and durable technique for the strengthening and rehabiliation of concretestructures serviced in corrosive coastal environment as the durability problem of suchstructures has been being more and more critical. Numerous investigations have beenconducted on Fiber Reinforced Polymer (FRP) reinforced concrete columns and thusgreat achievements have been attained among which some did relate to the field ofdurability. However, few of the existing works, focuses on the mechanical properties,especially the stress-strain relationship, of FRP reinforced concrete columns undercorrosive environment. In this paper, the corrosive coastal environment is firstsimulated by high-temperature wet-dry cycling and sulfate corrosion while the stresscorrosion is imposed by applying a constant pressure on a member. Thereafter, anexperimental study on FRP confined concrete columns under the interaction of stressand environmental corrosion were carried out to investigate the mechanism propertiesand durability of FRP reinforced concrete columns under the aforementionedcombined corrosion conditions. The main contents are provided in detail as follow:1) An experimental study on the durability of CFRP material under pure wet-drycycling, wet-dry cycling with irradiated ultraviolet rays, and salt-fog wet-dry cycling,respectively, were first carried out. The test results indicated that the longevity ofCFRP decreases with time under these three types corrorions; and the tensilestrength of CFRP will slightly increase when the CFRP was serviced in salt-fogwet-dry cycling and wet-dry cycling.2) The stress–strain curve of plain concrete columns and CFRP confinedconcrete columns was acquired through hydraulic testing machine with rigid supportelements.3) The durability of CFRP-confined circular concrete columns under purewet-dry cycling, wet-dry cycling with irradiated ultraviolet rays, and salt-fog wet-drycycling, respectively, were investigated by test. The test results indicated that theultraviolete rays irradiation has little influence on the the loading capacity of CFRP-confined concrete columns but has increased the ultimate axial strain 7%; while theloading capacity and the ultimate strain have been decreased 5% and 10%respectively by salt-fog wet-dry cycling; wet-dry cycling has little effect on theloading capacity and the ultimate strain of CFRP -confined concrete columns.4) An experimental investigation on the durability of CFRP-confined circularconcrete columns under the interaction of environment and loading conditions wereconducted, where 40% of the ultimate strength of the unconfined concrete conlumn combined with two corrosive environment conditions that are the pure wet-drycycling and salt-fog wet-dry cycling were considered and imposed. The test resultsindicated that the loading capacity and the ulimate axial strain of CFRP confinedconcrete column under the 120 days'interaction of salt-fog wet-dry cycling andloading conditions respectively droped about 8% and 20%; the loading capacity andthe ulimate axial strain of CFRP confined concrete column under the 60 days'interaction of wet-dry cycling and loading conditions respectively droped about 5%and 7%5) The commercial finite element software ANSYS were used to simulate themechanism properties and the failure process of CFRP-confined concrete columnunder the 120 days'corrosion of salt-fog wet-dry cycling. Compared with the testresults, it indicated that the preditions by the finite element model has a goodagreement with the relevant experimental results.