Effectiveness of mechanically anchored CRM and SRG jackets for enhancing torsional behavior of RC beams

Abstract

ABSTRACT Torsional failure presents a significant challenge in structural engineering, often causing rapid degradation and brittle failure in RC beams. This study experimentally investigates the effectiveness of Composite Reinforced Mortar (CRM) and Steel Reinforced Grout (SRG) jacketing for enhancing the torsional performance of RC beams, examining key design variables including mesh type (high-tensile steel versus GFRP), number of layers (single versus double), and the use of mechanical anchorage. Results show that all CRM and SRG jackets substantially improve torsional response by increasing stiffness and delaying crack initiation compared to unstrengthened beams. CRM consistently outperformed GFRP-mesh systems due to higher tensile capacity and more stable post-cracking behavior. Mechanical anchorage proved critical for fully mobilizing the composite, shifting failure from premature debonding to mesh rupture or localized concrete damage. The optimal configuration (steel mesh, double layers, and end anchors) achieved more than a 200% increase in ultimate torque and over 300% rise in absorbed energy relative to the original beam, demonstrating remarkable gains in ductility and toughness. Increasing CRM layers from one to two further enhanced cracking and ultimate torque, with anchored specimens showing distributed fine cracking rather than the single diagonal crack observed in the reference beam. These findings confirm that properly designed and anchored SRG and CRM jacketing provides a highly effective, robust solution for the torsional strengthening and rehabilitation of RC structures.