In-Plane Shear Behavior of Masonry Walls Strengthened with High-Ductility Concrete and Steel Connectors

This study investigates the influence of high-ductility concrete (HDC) strengthening configurations and steel connector positions on the in-plane shear performance of masonry walls in a retrofit scenario where the external masonry facade is retained while the original masonry wall is transformed into a steel frame-supported system, with steel connectors linking the exterior masonry to the interior frame. The experimental results demonstrate that HDC strengthening significantly enhances shear capacity by 17.1% to 98.4% compared to the unstrengthened reference wall. Internal HDC strengthening outperforms external strengthening by 40.1%, while double-sided strengthening provides a further 69.4% improvement over single-sided configurations. Additionally, perforation through brick centers (C-type) yields 104% higher cracking load and 26.8% higher peak load than perforation along mortar joints (J-type). The strengthening approach also markedly improves ductility, transforming brittle failure into ductile behavior. These findings provide a technical foundation for applying HDC in the seismic retrofitting of existing masonry buildings, including industrial and civil structures as well as substation masonry enclosures.