Beam column joints are the critical regions of reinforced concrete structures under seismic loading. There is an urgent need to evaluate their strength and to identify failure mechanisms of the joints. In this study, softened strut and tie model, which incorporates force equilibrium equations, compatibility conditions and material constitutive relation of the cracked concrete, are used to simulate the shear strength behaviour and to identify failure mechanisms of the interior beam-column joint. Using the softened strut and tie mechanism, formulation is developed for evaluation of shear strength in interior beam-column joint. Based on the formulations, a MATLAB program is developed. The results obtained using the program are validated with the results reported in the literature and studies are carried out to evaluate the influence of various parameters on the behaviour of the joints. The results of the studies will be helpful to arrive at the design strategy of the joints to ensure the desired failure mechanism.

Keywords: Interior beam-column joints, Failure mechanism, Softened strut and tie model, Joint shear strength.