Experimental study of predamaged columns strengthened by HPFL and BSP under combined load cases

After the ground motion, a large number of columns remain intact and can be retrofitted and reused. In this paper, to explore the effects of the loading scenario, predamage level and strengthening measures on the seismic performance of reinforced concrete (RC) columns, seven predamaged specimens strengthened with high-performance ferrocement laminate (HPFL) and bond steel plate (BSP) were tested. The results show that the bearing capacity, ductility, single-cycle energy dissipation and stiffness of all the predamaged specimens can be effectively restored and improved by this strengthening method for different loading cases. This strengthening method also significantly improves the shear capacity and changes the failure modes of the predamaged strengthened specimens from those of the corresponding predamaged unstrengthened specimens. The vertical eccentricity only slightly affects the seismic behavior of the specimens, while the horizontal eccentricity significantly increases the length of the failure region and reduces the seismic behavior of the specimens, considering the bearing capacity, energy dissipation capacity, and stiffness. The effects of different predamage levels are unique.