Behaviour and strength of RC columns retrofitted with steel angles and strips under eccentric axial loads

Abstract

This study intends to investigate the performance and behavior of steel jacketed Reinforced Concrete columns under eccentric loads. An experimental program has been designed to identify the behavior of jacketed RC columns under various levels of load eccentricity. This has been followed by a finite element based numerical simulation using constitutive material and appropriate contact modeling. In finite element model, both material and geometric nonlinearities were considered. The finite element models show fair agreement with the observed experimental results in terms of ultimate capacity and failure mode. This study also intends to investigate the performance of available analytical models to predict the capacity of steel angle and strip jacketed RC columns. The results of this study indicate that steel angle and strip jacketing scheme performs well under both concentric and eccentric loading. The capacity enhancement has been found about 240% under concentric loads compared to un-strengthened RC column, whereas the capacity enhancement is relatively more under eccentric loading compared to concentric loading. However, for this particular case eccentricity reduces the ultimate capacity of steel cage jacketed RC column of about 15% when eccentricity to column width ratio changes from 0 to 0.45. It also changes the ductile behavior of jacketed RC columns. From the finite element analysis, it has been found that the mean of experimental to numerical ultimate load capacity ratio was about 0.95, which indicates a fair agreement with slight overestimation. On the other hand, the available analytical model can predict load-moment interaction curve of steel jacketed RC columns with a high level of safety margin.