A model for non-linear dynamic analysis of substandard reinforced concrete members

Reinforced concrete (R/C) buildings designed according to older seismic codes represent a large part of the existing building stock; hence, it is important to be able to accurately assess their response to seismic actions. These substandard R/C buildings may contain structural elements that are prone to shear failure subsequent, or even prior, to yielding of their longitudinal reinforcement. This can potentially lead to loss of axial load resistance of vertical elements and initiate vertical progressive collapse of the building. In the present study, a model is put forward, which is able to capture the hysteretic behaviour of shear critical R/C elements up to the onset of axial failure. The model is able to account for gradual spread of inelasticity and shear-flexure interaction in the locations of the plastic hinges prior to the onset of shear failure as well as localisation of shear strains after the onset of shear failure; the latter constitutes a major advancement in the existing literature. The model is used to predict the behaviour of a cyclically loaded double-curvature specimen failing axially after shear failure and flexural yielding. The comparison of the analytical with the experimental results shows a very good agreement, both in terms of total response and of shear response.