Strengthening and Rehabilitation of RC Beams with FRP Overlays under Combined Shear and Torsion

This paper deals with evaluating the rehabilitation convenience of a damaged RC beam under the combined shear-torsion effect and retrieving its shear-torsion capacity by using FRP rolled strips. To this end, 9 specimens with 2.85 m lengths and clamped-clamped boundary conditions were made and tested under combined shear and torsion up to fracture (from zero loading eccentricity, corresponding to pure shear, to infinite eccentricity, due to pure torsion). Five of the specimens were ordinary (control) specimens considered as reference and four of them were strengthened with FRP strips from the beginning. Also, four of the ordinary specimens were rehabilitated after fracture by rubbing cement mortar on the cracked faces, then strengthened and tested like other specimens. Results indicated that rehabilitating and strengthening the beam will not only retrieve the initial shear-torsion capacity, but also increase the ultimate capacity up to 60 %. The increased capacity for the specimens strengthened from the beginning was 97%.