Torsional retrofitting of reinforced concrete beams using cementitious composite overlays, meshes, and mechanical anchorage

Résumé fourni par la source

The inadequate torsional capacity of many existing reinforced concrete (RC) beams, coupled with the limitations of conventional strengthening techniques in ensuring effective bond and composite action, represents a significant challenge in structural rehabilitation. One of the major practical challenges in the torsional strengthening of reinforced concrete beams is the difficulty of providing full wrapping from all sides due to the presence of adjoining slabs and walls that restrict access to the member. This study investigates the torsional performance of RC beams strengthened using cementitious composite overlays combined with steel anchors and surface-bonded meshes. Nine beams were tested, including one control and eight strengthened beams. Strengthening schemes included strain-hardening cementitious composites (SHCC) and ultra-high-performance concrete (UHPC) applied with one or two layers of glass fiber or welded steel meshes. Mechanical anchors were installed to enhance interfacial resistance and prevent premature debonding. Experimental results demonstrated significant improvements in cracking torque, ultimate torque capacity, torsional stiffness, and energy absorption. UHPC-steel mesh specimens achieved the highest performance, with up to 118% increase in ultimate torque and 371% increase in energy absorption compared to the control beam. Results confirm the effectiveness of hybrid composite strengthening systems for torsional retrofitting of RC members. A validated finite element model was further employed to conduct a parametric study on overlay thickness and mesh layer quantity, while an analytical formulation based on established torsional design equations was developed to predict the torsional capacity of the strengthened beams, providing complementary numerical and analytical verification of the experimental findings.