Dynamic analysis of reinforced concrete frames including joint shear deformation

The rehabilitation of existing buildings requires an assessment of their lateral load resisting capacity which may be limited by the strength and ductility capacity of their critical regions. From this assessment, a rehabilitation strategy can be formulated. Lack of adequate confinement and shear reinforcement in the beam–column joints of existing reinforced concrete frames may be the cause of brittle failure during a seismic event. Most of the nonlinear dynamic analysis programs assume infinitely rigid beam–column joints in concrete frames regardless of the reinforcement detail. To properly analyze existing structures, a joint element is proposed and introduced in the nonlinear dynamic analysis. The developed joint element accounts for inelastic shear deformation and bar bond slip. The response of three- and nine-story existing frames with joint elements when subjected to dynamic loading was compared with the response of frames with rigid joint assumption and the response of rehabilitated frames. The results show that the modelling of inelastic shear deformation in joints has a significant effect on the seismic response in terms of drift and damage. The rigid joint assumption was found to be inappropriate when assessing the behaviour of existing nonductile structures.