Energy-based modelling of in-plane fragility curves for the 2D ultimate capacity of Italian masonry buildings

Abstract

The high seismic hazard of the Italian territory and the vulnerability of its historic masonry heritage require the development of fragility curves that must be increasingly reliable and robustly correlated to exposure. To date, national-scale seismic risk analyses mainly use empirical curves derived from the statistical analysis of damage induced by past events. These curves have shown good reliability, but they correlate only with a few typological-structural characteristics of the building, such as the number of floors, the vertical structure typology or the construction period. The present research paper aims to overcome this limitation with a hybrid approach that provides a better exposure characterisation. Specifically, the proposed strategy integrates the SAVE and Piecewise Rigid Displacement (PRD) methods. SAVE is an empirical approach based on the damage assessment due to past seismic events used to identify a seismic behaviour of a structure, while the PRD method is a numerical approach that solves the boundary value problem for normal, rigid, no-tension material. It can model different structural typologies, and as a result, it also provides the value of the horizontal static multiplier that drives the masonry construction to collapse. An extended numerical campaign is carried out considering a sample of 750 masonry buildings distributed throughout the Italian territory and extracted from the PLINIVS typological database. Looking at each construction, first, a PRD analysis is conducted to define its seismic capacity, paying special attention to modelling construction details. After that, the SAVE method is used to classify the construction in a specific seismic vulnerability class, i.e., from A to C, with decreasing vulnerability. All the buildings belonging to the same class are then collected, and three fragility curves representative of the collapse state (one for each vulnerability class) are derived and validated against empirical and analytical ones commonly adopted in the Literature. The integrated methodology shows a good agreement between simulations and observations, confirming the viability of the proposed hybrid methodology for the large-scale assessment of masonry buildings, providing an effective strategy to plan mitigation and rehabilitation interventions.

Impact assessment caused by bradyseism phenomena in the Campi Flegrei area

“…In terms of exposure, data collection activities are planned that can provide more accurate information on the vulnerability distribution over the analyzed area. Finally, it is proposed to validate the empirical vulnerability model by comparison with curves built using analytical models (Perelli et al, 2023a). Frontiers in Built Environment frontiersin.org…”

“…The knowledge of the bradyseismic phenomenon in the Campi Flegrei area and its impact on the built stock is important for the (very dense) population safety. Extensive literature deals with the analytic study of the effects of soil motion on building behavior, especially for masonry structures, from a kinematic (Iannuzzo et al, 2018;Iannuzzo et al, 2021;Liguori et al, 2022;Maia Avelino et al, 2022;Perelli et al, 2023a) and static (Cusano et al, 2021;Montanino et al, 2022) standpoint.…”

An Hybrid Methodology for the Definition of Localized Collapse Curves for Unreinforced Masonry Structures

“…The admissibility of the deformation, given the PRD formulation, is enforced through the admissibility of the displacements at the interface (see Figure 3), that can occur only in detachment, as (11) where and are the nodal displacements of two adjacent blocks; the no-sliding conditions is enforced through: (12) being the tangential direction at the interface. Collecting all the interface and considering all the blocks of the discretization, the set of admissible displacement field is given by (13) and the solution in terms of the collapse multiplier is found as (14)…”

“…The local collapse curves have been compared with the global collapse curves obtained in [13]. The outcomes are shown in Table 6 with respect to mean μ and standard deviation σ in Figure 7 in terms of curves.…”

“…The seismic behavior class of each building is also defined using the SAVE method [12]. The data collection campaign had the task of defining the occurrence of each building typologies identified in [13], on which an analytical procedure based on the Piecewise Rigid Displacement Method can evaluate the pseudo-static collapse load, correlated to the geometry and construction details of the building. The procedure is specific for masonry structures, as it exploits the Heyman model for Rigid No-Tension materials [14,15].…”