TORSION ENHANCEMENT OF REINFORCED SELF-COMPACTING CONCRETE BOX BEAMS USING INTERNAL FRAMED STEEL STIFFENING RIBS

Abstract

Researches concerning internal torsional strengthening of box beams are very little, since few researchers may study such method of strengthening. This research adopts employing of internal Framed Steel Stiffening Ribs (FSSRs) to strengthen reinforced Self-Compacting Concrete (SCC) box beams subjected to pure torsion. These FSSRs were fabricated to be fully bonded with SCC through using of bolts as shear connectors. Four specimens (the first was a reference one with no strengthening and the other three were strengthened with one, three and five FSSRs, respectively) of reinforced SCC were tested under effect of pure torsion up to failure. All specimens have the same dimensions and reinforcement. The effect of FSSRs presence and their number on torsional capacity was studied. Also, applied torque-angle of twist relation at end, quarter and mid span were studied. Test results show that the ultimate torsional capacity is increased by 45.7 %, 75.5 %, and 122.4 % for specimens strengthened with one, three and five FSSRs, respectively, as compared with reference specimen. Presence of FSSRs tends to reduce deformations where deformations decrease with increasing of FSSRs number. It is concluded that the torsional capacity of a reinforced SCC box beams can be enhanced using internal Transverse FSSRs. The number of used internal FSSRs have main effect on the amount of enhancement.