Experimental Research On The Seismic Performances Of Damaged Reinforced Concrete Columns Strengthened With Carbon Fiber Reinforced Plastics

Taking human financial and material resources conditions into consideration, it isrecommended that taking some technical measures to reinforce and strengthen thedamaged reinforced concrete structures rather than to break down and rebuild all ofthem. It is well known that CFRP wraps increase bearing capacity and deformationductility of undamaged reinforced concrete columns. However, the behavior of CFRPstrengthened damaged R/C columns is not yet fully understood, and the currentstrengthening codes still exists the blind area of formula about calculation of shearbearing capacity of reinforced concrete damaged columns. The study is carried out as astep towards improving this status. Experimental and analytic-al studies in this articleare focused on damaged reinforced concrete columns strengthened with Carbon FiberReinforced Plastics.To analyze ant-seismic performances the damaged reinforced concrete columnsstrengthened with CFRP, four concrete columns were tested under constant axial loadand cyclically lateral load in this paper, one contrast specimen (not strengthened) andthree columns were pre-damaged and tested strengthened with CFRP. The twoparameters of test specimens included the axial compression ratio and the pre-crackwidth. Through pseudo-static test the bearing capacity, the hysteretic curve, the skeletoncurve, ductility, energy dissipation, strength deterioration and rigidity degradation wereanalyzed has been analyzed and contrasted under the different parameters.The test results indicate that：(1) The damaged reinforced concrete columns strengthened with CFRP still haveplump hysteretic curves and excellent energy consumption. Good ductility and eveningdeformation ability after the columns reach ultimate load. Deformation ductilitycoefficient of the columns after strengthening is between4.28and6.34; stiffnessdeterioration and strength deterioration were slowly.(2) The axial compression ratio and the pre-split crack width have enormousinfluence on the seismic behavior of the damaged reinforced concrete columnsstrengthened. In the same axial compression ratio, the damaged more severe columnthrough the strengthening treatment could get the same bearing capacity of the damagedlighter column. In the same crack width, the ultimate bearing capacity of strengtheneddamaged column with higher axial compression ratio increase was obviously. This conclusion could be provided theory support for damaged reinforced concrete columnsthrough the strengthening treatment.The “arch-truss” model theory was adopted to analyze the shear bearing capacityof the damaged R/C columns strengthened with CFRP in this paper, the loss coefficientCFRPand the simple formula of shear bearing capacity after strengthening was putforward for the damaged R/C columns strengthened with CFRP. The simple formula ofshear bearing capacity compared with “Technical Specification for StrengtheningConcrete Structure with carbon fiber reinforced plastics” and “Design code forStrengthening Concrete Structure” proposed the formulas of shear bearing capacity. Bycomparison, the formulas calculating result recommended by specification is biggerthan experimental results and could not reflect the influence of the crack width. Thesimple formula calculating result of shear bearing capacity given in the paper agreesapproximately with the experimental values and could reflect the influence of the crackwidth. The simplified formula is feasible.