Restoration of Vertical and Lateral Stability of a Distressed RC Structure Adopting RC Jacketing and Composite Structural Members

Abstract

AbstractWhen vertical structural members present in a structure undergo damage, it causes the overall load carrying capacity and stability of the structure to reduce. The present work focuses on restoring the lateral stability and the load carrying capacity of a five storey reinforced concrete structure that has undergone damage when subjected to an earthquake. The reinforced concrete structure considered in this study is an old structure that has not been designed for earthquake resistance. A nonlinear seismic analysis adopting response spectrum method is carried out on the reinforced concrete structure that is constructed in zone V. After carrying out the earthquake analysis, it is learnt that few columns have failed because the RC columns have not been designed for resisting earthquake loads. The internal forces and lateral displacements of such failed RC columns present in the structure are assessed to study the extent of damage that has taken place in such RC columns and RC beams. It is observed from the results that the lateral storey displacements are larger in the structures having the RC columns and beams not designed for seismic resistance when subjected to earthquake loading. When RC jacketing is applied on to the distressed RC columns present in structure and the seismic analysis is there after carried out, it is observed that the lateral storey displacement has reduced, there by improving the lateral stability of the structure whose damaged RC columns are retrofitted for future earthquakes. In the case of RC columns, only those columns that have undergone large lateral displacement and have been damaged excessively are replaced with composite columns (encased column). The connection between the new replaced composite column and the existing RC floor beams is considered as fixed in the analysis, as in the actual site condition, the I-section and reinforcement present in the encased composite columns are welded to the reinforcement of the RC beams (top and bottom floor beams). It is observed from the analysis of the structure that houses the encased columns, that is provided as a replacement in place of the excessively damaged RC columns, there is a reduction in lateral storey displacement and there is a comparative increase in moment and lateral shear carrying capacity. It is observed from the results that, the RC jacketing of damaged RC columns tends to have lower lateral storey displacements when compared to the damaged RC columns that are replaced adopting encased columns having the same size of the original columns.KeywordsRetrofittingRC jacketingComposite columnEncased columnsEarthquake damage