PSI - Issue 77

Humberto Varum et al. / Procedia Structural Integrity 77 (2026) 665–672 Author name / Structural Integrity Procedia 00 (2026) 000 – 000

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Modern RC buildings are typically designed to ensure a global ductile failure mechanism, characterized by the intentional formation of plastic hinges at beam ends, mitigating shear collapse. Several studies demonstrated, in the other hand, that corrosion substantially affects damage states, failure mechanisms, flexural capacity, and energy dissipation (Aminulai et al., 2023; Meda et al., 2014; Yang et al., 2016; Yao et al., 2019). This issue may be even more pronounced in existing old RC buildings, which are often susceptible to brittle soft-storey collapses (Berto et al., 2020). Despite the importance of this issue and numerous studies in corrosion field, there exists limited research addressing the effects of corrosion on the seismic response of RC structures subjected to lateral loading (Caixinhas et al., 2025). It is imperative to address efforts in experimental and numerical analyses of RC models to better predict structural behaviour in seismic events and to improve design aspects, considering corrosion effects in seismic response of RC structures. 6. Conclusions Recent seismic events have consistently demonstrated that irregular structural responses can lead to severe human and economic consequences. Most of the existing structures exhibit such irregular behaviour. Therefore, in both the assessment of existing RC buildings and the design of new constructions, particular attention must be directed toward the following aspects: • Vertical irregularity: More specifically the soft-storey condition in ground floor due to shift in inter-storey height, dimensions and position of openings, distribution of the masonry infill walls; • Irregularity in plan: Torsion. The evolution of seismic codes and design practice has been characterized by a growing emphasis on the ductile structural systems, achieved through the enhancement of the ductility and deformation capacity of structural elements. Both, buildings regularity verification and the infill walls contribution to seismic performance must be carefully considered and assessed. Additionally, for old RC existing buildings, the combined effect of corrosion and structural irregularities is considered deleterious to seismic response, due to the shift in the collapse modality, which leads to unforeseen structural damages. On regards to the impact of irregularity, namely the reducing the q-factor or R-factor in force-based design and restricting the methods of analysis allowed, despite the evolution of the seismic codes, further calibration and validation of the rules proposed by those codes should be undertaken for various structural systems and forms of irregularity, supported by extensive numerical analyses and experimental investigations. Acknowledgements This work is financially supported by national funds through the FCT/MCTES (PIDDAC) under the project 2022.05721.PTDC with DOI 10.54499/2022.05721.PTDC (https://doi.org/10.54499/2022.05721.PTDC), and by Funding - UID/04708 of the CONSTRUCT - Instituto de I&D em Estruturas e Construções - funded by Fundação para a Ciência e a Tecnologia, I.P./ MCTES through the national funds. References Afsar Dizaj, E., Kashani, M.M., 2022. Nonlinear structural performance and seismic fragility of corroded reinforced concrete structures: modelling guidelines. European Journal of Environmental and Civil Engineering 26, 5374 – 5403. https://doi.org/10.1080/19648189.2021.1896582 Amini, S.N., Rajput, A.S., 2024. Seismic response assessment of ductile reinforced concrete columns affected by corrosion and axial load variations. Structures 65. https://doi.org/10.1016/j.istruc.2024.106699 Aminulai, H.O., Robinson, A.F., Ferguson, N.S., Kashani, M.M., 2023. Nonlinear behaviour of corrosion damaged