Effect Of Aspect Ratio On Axial Compressive Behavior Of Steel Reinforced Concrete Rectangular Columns

The performance of axially compressed steel reinforced concrete(SRC)rectangular short columns confined with CFRP strips were studied by experimental investigation,numerical simulation and theoretical analysis.Nine specimens were designed and loaded,which considers the parameter aspect ratio.The failure modes and mechanism of confined columns were studied through the experiments.All of the CFRP-confined columns failed finally in the fracture of CFRP laminates.Columns with higher aspect ratio showed more obvious the phenomenon of failure and more relieved the brittle failure.With the increase of aspect ratio,the effective tensile strain coefficient of CFRP gradually reduced under the peak and ultimate capacity and distribution of lateral strain of CFRP in circumferential direction was non-uniform.The failure modes transfered from hardening confinement to softening confinement.A finite element analysis model was established to simulate the compressive behavior of confined SRC column with CFRP strips by ABAQUS software,the numerical results were in good agreement with the experimental results.The parameter analysis model was established to simulate based on the numerical simulation.Therefore,the scope of aspect ratio were expanded and the number of reinforced concrete(RC)rectangular columns were increased.The numerical results showed that,as the aspect ratio increased,the strength increment decreased and the ductility increment increased.The strength increment of SRC columns versus aspect ratio was more moderate with respect to the corresponding RC columns.It revealed that strength rehabilitation could be easily obtained for specimen with lower sectional aspect ratio,while ductility rehabilitation could be easily got for specimen with higher aspect ratio.With the same aspect ratio,more CFRP layers must be needed for the hardening confinement of SRC columns.There were strongly and weakly confined region in reinforced concrete rectangular columns cross section.For SRC columns,the concrete around the steel was even more strongly confined.As the aspect ratio increased,the proportion of the high stress region decreased.When the aspect ratio reached 2.0,the proportion of the high stress region of the SRC columns were still large,and they still showed good confinement.According to the existing research,the maximum aspect ratio was obtained from the calculating formula.The calculating formula of the lateral confining strength were proposed.The stiffness ratio K of SRC columns was the lateral stiffness divided the axial stiffness.The effect of steel were concerned as well.A new model for the strength of steel reinforced concrete rectangular columns confined with CFRP strips was proposed by means of data fitting.