Evaluations of the effectiveness of the near‐surface mounted steel materials in strengthening short <scp>RC</scp> wall‐like columns with openings

Abstract In practice, reinforced concrete (RC) wall‐like columns often have openings to facilitate building services, which creates stress concentrations around the opening, resulting in the weakening of their load‐carrying capacity. This study proposes innovative strengthening methods using near‐surface mounted (NSM) incorporating steel materials to improve their load‐carrying capacity. A series of tests was conducted to study the effectiveness of NSM steel wires and bars as strengthening methods on walls with/without different opening shapes. The studied parameters include the existence of an opening (walls with and without openings), the opening shape (square and circle), the strengthening materials (steel bars and wires), along with the configuration of strengthening (vertical and horizontal). The experimental results show that NSM strengthening significantly improves both the axial load capacity and ductility of the walls. Walls with circular openings outperformed their square counterparts due to a more favorable stress distribution. While the ultimate strength of the solid unstrengthened walls incorporating a circular and square opening was 9% and 24% lower than the control specimen, respectively, strengthening walls consisting of circular openings using the NSM method resulted in an increase of the ultimate load and the energy absorption capacity by 5% and 60%, respectively. Numerical models of the tested walls are carried out and validated against the experimental results. It is seen that the numerical model can accurately predict the failure modes and load–displacement performance. Additionally, analytical studies using established design equations are carried out to estimate the ultimate load of such walls.