PSI - Issue 77

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

667

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Several authors performed current seismic codes comparison, regarding structural irregularities (Das et al., 2021; Santos et al., 2024a; Varum et al., 2022b). Important conclusions from their work can be highlighted: • There are, throughout several seismic codes, a consensus on the desired characteristics of a seismic-resistant structure, namely simplicity, symmetry, uniformity and redundancies; • The issue of structural irregularity is addressed in all assessed seismic standards, even though with differences in quantitative or qualitative nature of in each irregularity criteria. Corrosion´s impact on steel and concrete, including reduction in ductility, confinement and strength, can compromise structural performance. It is marked by the decline in strength and, more critically, a reduction of structural displacement capacity, often leading to the change of collapse modality and to unforeseen failures. This issue was highlighted in some numerical studies aimed at capturing the effect of corrosion on the seismic performance of the entire building (Afsar Dizaj and Kashani, 2022; Berto et al., 2009). Such a problem can be even higher in existing RC buildings characterized by the strong beam/weak column hierarchy typical of design performed only towards vertical loads, frequently exposed to brittle soft-storey collapses (Berto et al., 2020). This work seeks to present a comprehensive overview of the damages observed in recent seismic events, especially due to RC structural irregularities. Additionally, it will be assessed the infill walls disposition impacts in RC structures´ seismic response. Finally, the combined effect of corrosion and vertical irregularity on RC structure seismic response is discussed.

Nomenclature DC1

Ductility class 1 Ductility class 2

DC2 DC3

Ductility class 3 NRHA Nonlinear response history analysis RC Reinforced concrete UBC Uniform Building Code

2. Lessons learned from seismic events The development of seismic codes has been largely supported by field observations of building performance during recent earthquake events. Post-earthquake damage reconnaissance missions have enabled the technical and scientific community to identify the causes of both local and global structural failures, as well as to distinguish between appropriate and inadequate construction practices in earthquake-resistant systems (Varum et al., 2022a). Based on post-earthquake survey damage analysis in major recent seismic events, Varum et al. (Varum et al., 2022b) established the most common types of damages in RC buildings as demonstrated in Table 1. The observed structural damage shows that deficiencies in detailing and design, such as inadequate confinement, shear weaknesses, and undesirable mechanisms, undermine the ductility and overall safety of buildings. The recommendations highlight the need for designs based on rigorous detailing, proper construction practices, and the capacity design concept to mitigate both local and global failures under seismic actions.