SRG vs SRP Jacketing in Shear Strengthening of Reinforced Concrete Beams

Abstract

Most of the existing reinforced concrete (RC) buildings were built according to previous generation of codes when seismic detailing was at a primitive stage of knowledge. One of the deficiencies is related to the insufficient transverse reinforcement which could lead to brittle failure modes jeopardising the integrity of RC buildings. To increase the resilience of the existing building stock and protect human lives from devastating future earthquake events strengthening measures need to be adopted.

Externally bonded reinforcement, such as Fibre Reinforced Polymers (FRPs), are well established and used widely in shear strengthening applications in the form of closed or three-sided jackets. This system comprises different type of fabrics (carbon, glass, aramid) embedded in resin. A variation to this technique is the Steel Reinforced Polymers (SRPs) where Ultra-High Tensile Strength Steel (UHTSS) textiles are used in place of the composite fabrics. To develop a more environmentally friendly solution with improved performance at high temperatures and lower cost, resin has been substituted by cementitious mortar and the Steel Reinforced Grout (SRG) composites have been developed.

This paper investigates experimentally the efficiency of SRP and SRG jacketing in strengthening shear critical reinforced concrete (RC) beams with a shear span ratio equal to 2. All tested beams have the same geometry and are subjected to monotonic asymmetric three-point loading. Key parameters of this study are the density of UHTSS textiles (4 and 8 cords/in), the strengthening configuration of the jackets (U-shaped and fully wrapped) and the concrete strength of the beams (22 and 57 MPa). Experimental evidence demonstrates that both SRP and SRG jacketing are efficient and can improve the shear strength of deficient beams. In case of the SRG and SRP fully wrapped beams, the mode of failure changes from brittle to ductile.