Torsional Strength of Ferrocement “U” Wrapped Normal Strength Beams with only Transverse Reinforcement

Abstract

Structural repair and rehabilitation of concrete structures is necessary for all deteriorated or damaged structures to restore and enhance the load bearing capacity as well as to increase the life span of the structure In the recent past 3Rs of construction Technology (Retrofitting, repair and Rehabilitation) became popular due to the natural calamities or the updates of the codal provisions. Use of FRPs have been gaining world wide acceptance as retrofitting material for their high strength, light weight and good fatigue life. However, from cost benefit point of view ferrocement can be used as wrapping for rehabilitation of deteriorated or damaged reinforced concrete beams. Ferrocement, a thin structural composite material, exhibits better crack arresting capacity, higher tensile strength to weight ratio, ductility and impact resistance. Hence it can be used as an alternative for FRPs in the field of repair and rehabilitation. Very little information is available from literature on the repair and rehabilitation of reinforced concrete beams with ferrocement wrapping especially in resisting pure torsional loads. Repair and rehabilitation of the distressed concrete structures is well addressed by researchers for the basic structural actions such as axial loads, flexure and shear in past few years, but torsional repair and rehabilitation has not attained much importance in research due to its complex nature and its occurrence with other basic structural forces. Circulatory torsion induces shear stresses on all four sides and would be well resisted by closed form reinforcement. But due to monolithic construction of beam and slabs, U wrap retrofitting is the most practical solution. Experimental results and analytical models of previous researchers revealed that wrapping on three sides of the beam also enhance the ultimate torsional strength. An experimental investigation is conducted to address the torsional capacity and twist of reinforced concrete beams with reinforcement only on transverse direction and strengthened with ferrocement “U” wraps (leaving the top side free from wrapping) as this situation is more common in the rehabilitation of concrete structures. The results revealed that single type of reinforcement (only on transverse direction) is not an effective way of enhancing the torsional strength while increase in toughness is found to be marginal