Numerical Modeling of FRP-Strengthened Masonry Structures Using Equivalent Frame Models

The present study focuses on enhancing the seismic resistance of existing masonry structures. To that aim, the use of fiber-reinforced polymer (FRP) strengthening serves to improve structural behaviour by attaching FRP strips to the masonry walls. Despite substantial study on the influence of such strengthening interventions on structural elements, computationally efficient numerical models capable of adequately depicting this phenomenon remain scarce. This paper therefore endeavors to develop and validate a numerical modeling approach to capture the effect of FRP strengthening on masonry panels. The proposed modeling approach leverages a newly developed macro-element, capable of capturing both in-plane and out-of-plane modes of failure. This is achieved by incorporating the FRP intervention into the section model through the addition of fibers, while the effect of transversal FRP strips on shear strength is accounted for by a proportional increase in the cohesion within the shear strength equation. This approach is further illustrated through a case study of a masonry building tested on a shake table. Overall, the suggested modeling strategy successfully predicts both the in-plane and out-of-plane response, indicating that equivalent frame models may successfully describe the response of masonry structures with FRP-strengthened walls. To conclude, the models discussed in this study can be employed for a time-effective analysis. Additionally, it can assist in determining the best strengthening strategy for potential retrofitting. For cultural heritage sites, where unnecessary retrofitting should be avoided, this aspect is particularly essential.