Behaviour of the partial steel-jacketed preloaded RC columns under concentric axial load: Fid-Bau Portal

Behaviour of the partial steel-jacketed preloaded RC columns under concentric axial load

Akter, Farjana / Begum, Mahbuba

This research primarily intends to investigate the behaviour and strength of the deficient RC columns strengthened with partial steel jacketing method. For this purpose, an experimental investigation was carried out on seven deficient RC columns with a low concrete strength of 15.2 MPa. Keeping analogy to the practical situation, columns were made deficient further by preloading to the 70% of their ultimate compressive load. The partial steel jacketing method was made with four equal leg steel vertical angles and uniformly spaced horizontal strips. All the columns were tested under concentric axial loads till failure. The effect of the column preloading state was the main parameter in this study. The influence of steel angle ratio and spacing of the horizontal strips were investigated for the column 70% preloading state. However, this study resulted in a significant improvement in ultimate load (ranging from 87% to 186%) and ductility (ranging from 31% to 67%) of the deficient preloaded RC columns with this particular partially steel jacketing method. This enhancement in ultimate capacity was obtained to be reduced by 27% due to the application of 70% preloading to the RC columns before strengthening. The increase in steel angle ratio from 4% to 7% provided highest contribution in improving the ultimate strength of the preloaded column with respect to the un-strengthened (Ref) column. On the other hand, decreasing the strip spacing from 300 (2d) to 150 (d) mm resulted in an increase in capacity of the preloaded columns by an average value of 15% only. However, the ductility of the columns was improved significantly about 60% due to the reduction in strip spacing from (2d) to (d).