PSI - Issue 78

Ahmed Mabrouk et al. / Procedia Structural Integrity 78 (2026) 960–967

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Fig. 5. Average frame performance level ratios, for all frame configurations

5. Conclusions This study investigated the seismic response of RC frames with clay masonry infill walls, using a calibrated macro model capable of simulating the coupled IP and OOP behaviour of infill panels. A key contribution of this work is the re-implementation and re-calibration of the infill macro-model proposed by Donà et al. (2021) within the STKO – OpenSees environment. The model was calibrated against experimental data for both unreinforced (URM) and strengthened infill panels, accurately reproducing their cyclic IP and OOP response across multiple damage states. The calibrated parameters were then used in nonlinear TH analyses of a three-bay, eight-storey RC frame, assessed under varying PGA levels and seven natural ground motions. Key findings include the following: URM infills, while enhancing initial stiffness, are highly vulnerable to OOP collapse once damaged in-plane. This behaviour was captured through displacement-based removal logic that simulates panel expulsion. Strengthened infills (F panels) exhibited superior performance, with no collapse observed up to = 0.5 . Their presence delayed or shifted critical frame limit states, reducing flexural demands and improving global drift behaviour. The bare frame, in contrast, exhibited early onset of flexural and drift-related damage, particularly at higher PGAs, highlighting the vulnerability of traditionally designed RC structures without infill contribution. Overall, the study confirms the importance of modelling infill walls not only for their stiffening effect but also for their potential to trigger or delay critical damage mechanisms. The proposed modelling approach allows for detailed damage tracking, realistic panel failure simulation, and is adaptable for broader parametric or retrofit studies. Future work will extend this framework to include different infill types, and three-dimensional frame configurations, with the goal of supporting the definition of guidelines and standards on the assessment of RC infilled frames, with specific focus on the IP/OOP infill interaction. Acknowledgements This work was supported by POROTON® consortium and partially funded by the Italian Department of Civil Protection and ReLUIS, within the framework of the ReLUIS-DPC Project 2024 – 2026 – Work Package 10 Task 3: “Non -structural masonry”. Special thanks to G. Zanellato, for his support in calibration and analysis during his MS Thesis.