PSI - Issue 77

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

668

4

Table 1. Common post-earthquake RC structures damages and recommendations.

Damage Type

Description of damage

Recommendations

1

Stirrups and hoops inadequate quantity and detailing, regarding the required ductility

The concrete core in the plastic hinge region should be sufficiently confined to mitigate strength degradation, prevent brittle failure arising from shear and flexural demands, and enhance overall ductility For smooth reinforcement bars, the code-based approach and the procedures employed in seismic safety assessments for estimating flexural strength capacity tend to overestimate the actual flexural performance of RC elements Issues related to shear strength and confinement are particularly pronounced in corner columns, especially in buildings exhibiting eccentricity between the centres of mass and stiffness. The corner columns should be designed with the highest confinement requirements

2

Longitudinal reinforcement detailing (bond, anchorage and lap-splices)

3

Shear and flexural capacity of elements

4 5 6 7

Inadequate shear capacity of structural joints Strong-beam weak-column mechanism

Give more importance to design detailing Design considering capacity design approach

Short-column mechanism

Structural irregularities (in plan and/or in elevation: torsion, “weak - storey” and “soft storey”)

Masonry infill walls cannot be considered non-structural or secondary elements and disregarded from the building behaviour. The infill walls assume a more than secondary role since they can modify the global structural behaviour

8 9

Pounding

Secondary elements (cantilevers, stairs, etc.)

10

Damages in non-structural elements

3. Structural irregularities The impact of structural irregularities in the RC building structures’ seismic performance has been highlighted in several post-earthquake damage reports (Varum et al., 2022a). Several structural damage mechanisms, such as torsion caused by asymmetrical masonry infills, first-soft-story buildings, and flaws in reinforcing detailing, have frequently been recognised as inappropriate structural configurations (Jara et al., 2020). Regarding the impact of irregularities on demand amplification along building height, for low-rise buildings, torsion creates an additional acceleration component in the perpendicular direction of the analysis, which increases with floor eccentricity (Landge and Ingle, 2021; Ruggieri and Vukobratović, 2024) . The findings were correlated with the floor eccentricity, the elevation of the node under consideration, and the yielding force and ductility in relation to the nonlinear field. A non-uniform distribution of infill walls in plan or elevation is frequently associated with structural irregularities. Despite infill walls are non-structural elements, several studies suggest that they are essential on the structural seismic behaviour and are responsible for a significant part of the human, material and economic losses (Dias-Oliveira et al., 2022; Falcão Moreira et al., 2023; Varum et al., 2022a, 2022b). The design of the structures should guarantee proper and balanced stiffness, strength and ductility of the structural elements, considering the standards prescriptions on seismic loading demands. Nonetheless, some seismic design codes dismiss the contribution of the infills panels to the seismic structure response. Their influence is usually considered with simplified procedures. It is well recognized that structural system benefits from increased stiffness, strength, and energy dissipation from the infill walls. Nevertheless, their global response may be adversely affected, contingent on their characteristics, in-plan and in-elevation distribution. The infills diminish the deformation capacity and potentiate failure mechanisms development that the structural members were not designed to. Assessing the evolution of first and second generation of Eurocode 8, in the regularity in plan section, except in the plan configuration criteria (Varum et al., 2022a). Regarding vertical irregularities, the first generation of Eurocode 8 is more qualitative in the criteria assessment. However, the new draft presents a more quantitative approach (Santos et al., 2024a, 2024b). These criteria are presented in Table 2.