An experimental study about unreinforced masonry panels strengthening with CFRP: Out-of-plane failure

Abstract

This study presents an experimental investigation into the out-of-plane behavior of unreinforced masonry (URM) panels strengthened with carbon fiber-reinforced polymer (CFRP) strips. Motivated by the widespread collapse of masonry walls observed during the 2023 Kahramanmaras, earthquakes, the research aims to evaluate the effectiveness of various CFRP configurations in enhancing structural performance under out-of-plane loading. A total of ten medium-scale masonry panels were tested under monotonic three-point bending, including a control specimen and nine strengthened specimens featuring different numbers of strips (one, two, and full-wrap) and layer configurations (one, two, and three layers). Key parameters such as load-carrying capacity, displacement at peak load, initial stiffness, energy dissipation, and strain behavior were measured and analyzed. Results demonstrate that CFRP strengthening significantly improves the out-of-plane resistance of masonry panels, with full-wrap and multi-layered configurations yielding the most pronounced gains. While debonding was the dominant failure mode in limited-strip specimens, full-wrap specimens reached the compressive capacity of the brick units before failure, indicating strong bond performance. The study also discusses the implications of scale, absence of anchorage, and limitations associated with monotonic loading. Findings contribute valuable insights into the development of practical and efficient CFRP-based retrofitting strategies for seismic risk mitigation in existing masonry structures.