Experimental investigation of the effects of concrete strength and axial load ratio on the performances of CFRP-wrapped and externally collared RC short columns

•RC short columns were tested with concrete strength and axial load ratio parameters.•Reference columns were ideal columns with well transverse reinforcement detail (Ø10/100).•The columns with stirrup spacing Ø10/150 were strengthened with CFRP sheets and external steel collars.•Shear interaction was more effective for Ref columns than for strengthened columns.•Seismic performances of the proposed applications were higher than the ideal Ref columns.