Seismic rehabilitation of reinforced concrete columns through confinement by steel collars

The research presented in this thesis is a part of a larger research program on the seismic rehabilitation of reinforced concrete frames using steel plate shear walls. Steel plate shear walls are highly ductile, but seismically deficient reinforced concrete frames tend to be incompatible due to their lack of ductility. Therefore, this rehabilitation scheme requires the improvement in ductility of the concrete frames. The research presented herein is a comprehensive experimental and analytical investigation into the improvement of behaviour of seismically deficient reinforced concrete columns through confinement by steel collars. The experimental research was divided into two phases.; In the phase 1 experimental program, the axial behaviour of collared columns was investigated and it was demonstrated that a significant enhancement in both strength and ductility can be achieved. In the phase 2 experimental program, the behaviour of collared columns under axial load and lateral cyclic loading was investigated. The results showed that the confinement arising from the presence of the collars leads to excellent cyclic behaviour, indicating that this scheme shows promise of being an effective means of rehabilitating seismically deficient reinforced concrete columns.; Existing concrete confinement models are unable to predict the behaviour of collared columns because of the lack of an explicit flexural stiffness parameter. Therefore, a new confinement model has been developed that takes into account the significant flexural stiffness of the confining elements. This model requires as input the behavioural curves of collars in terms of the confining pressure versus lateral strain relationships. These curves are obtained through finite element analyses. Non-dimensional models were also developed for the confining behaviour of HSS collars and solid steel collars with rigid corner connections.; Using the confined concrete material curves obtained by the proposed model, good predictions of the behaviour of the axially loaded columns tested in phase 1 were obtained. Moreover, envelopes to the moment versus drift hystereses were determined using the model that showed very good agreement with the experimental results up to a lateral drift of about 10% for columns tested with a long shear span and 5% for columns tested with short shear span in the phase 2 experimental program.