NUMERICAL MODELING FOR BACKBONE CURVE AND ULTIMATE POINT FOR FLEXURE-SHEAR DOMINANT REINFORCED CONCRETE COLUMNS
Supervisor: Susumu KONO
A displacement based evaluation approach, namely Axial Shear Flexure Interaction (ASFI), is used in determining backbone curve and ultimate point for flexure-shear dominant reinforced concrete columns, considering interaction among axial, shear and flexure mechanisms. Conventional section analysis technique is employed to predict flexure behaviour and Modified Compression Field Theory is adopted to determine the shear behaviour. Ultimate point and backbone curves were estimated using this approach for four reinforced concrete columns which were critical in shear and flexure-shear, and then compared with experiment results. Prediction of ultimate point and backbone curve are not satisfactory using ASFI for the columns. Considering many aspects of material constitutive laws, their definitions in the analytical model and different mechanisms acting inside the model, concrete compression softening is thought to be a very influencing variable to predict the ultimate point and backbone curve for shear and flexure-shear dominant reinforced concrete columns. A parametric study is conducted considering different degrees of concrete compression softening with increasing principal tensile strain to find out the sensitivity of strength reduction in cracked concrete for predicting these structural parameters. From this study, one of the options for simulating the continuous weakening behaviour of cracked concrete found to be effective in determining ultimate point and backbone curve for shear and flexure-shear dominant reinforced concrete columns.