PSI - Issue 78

Marina Serpe et al. / Procedia Structural Integrity 78 (2026) 1000–1007

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Phase 1: Definition of Case Studies 1

Step 1.1 : Selection of reference geometry; Step 1.2 : Parametric variation of geometrical and structural features; Step 1.3 : Definition of settlement scenarios.

Step 2.1: Selection of the numerical modelling; Step 2.2 : Pushover analysis without settlement; Step 2.2 : Post-Settlement pushover analysis. 2 Phase 2: Numerical Modelling and Pushover Analyses

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3 Phase 3: Fragility Curves Derivation

Step 3.1 : Evaluation of capacity curves; Step 3.2 : Definition of seismic demand and limit states; Step 3.3 : Derivation of fragility curves.

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Fig. 1 Schematic representation of the numerical strategy adopted.

In Phase 1 (see section 3), a population of URM façades was defined to enable a probabilistic assessment. Starting from a selected reference geometry, a set of parametric variations was introduced, namely, changes in opening percentages and floor stiffness, to generate a representative sample of wall configurations. In addition, several differential settlement scenarios were defined, varying in terms of magnitude, location, and extent, in order to assess their influence on seismic performance. In Phase 2 (see section 4) following the approach used in a previous work (Serpe Marina et al. 2025), the façade configurations developed in Phase 1 were modelled and analysed using the software Abaqus, following a macro element homogenized modelling approach to describe masonry behaviour and a semi-coupled approach for settlement application at the façade base. This was achieved applying a predefined vertical downward displacement to a movable rigid block (representative of the rigid foundation) connected at the façade through a no tension interface. For each configuration, two pushover analyses were conducted: • First pushover analysis : without any settlement, to evaluate the baseline seismic capacity; • Second pushover analysis : after the application of foundation settlements, to assess the capacity reduction due to prior damage. This two-step approach allowed for a direct comparison of seismic performance indicators, such as strength, stiffness, and displacement capacity, between the pushover curves obtained for the same structural configuration, with and without prior settlement applied. In Phase 3 (see section 5), fragility curves were derived based on the capacity curves and performance limit states. Both the configurations were analysed, enabling a probabilistic evaluation of damage likelihood under seismic loading. The cumulative fragility curves derived for the pre-damaged façades were compared with those obtained for the configurations without settlement application. This comparison made it possible to quantify the increase in seismic vulnerability due to pre-existing settlement-induced damage and to identify the most critical settlement scenarios among those investigated. The following sections provide a detailed description of each phase and present the key results of the study.