The heuristic vulnerability model: fragility curves for masonry buildings

Abstract

In the framework of seismic risk analyses at large scale, among the available methods for the vulnerability assessment the empirical and expert elicitation based ones still represent one of most widely used options. In fact, despite some drawbacks, they benefit of a direct correlation to the actual seismic behaviour of buildings and they are easy to handle also on huge stocks of buildings. Within this context, the paper illustrates a macroseismic vulnerability model for unreinforced masonry existing buildings that starts from the original proposal of Lagomarsino and Giovinazzi (Bull Earthquake Eng 4(4):445–463, 2006) and has further developed in recent years. The method may be classified as heuristic, in the sense that: (a) it is based on the expertise that is implicit in the European Macroseismic Scale (EMS98), with fuzzy assumptions on the binomial damage distribution; (b) it is calibrated on the observed damage in Italy, available in the database Da.D.O. developed by the Italian Department of Civil Protection (DPC). This approach guarantees a fairly well fitting with actual damage but, at the same time, ensures physically consistent results for both low and high values of the seismic intensity (for which observed data are incomplete or lacking). Moreover, the method provides a coherent distribution between the different damage levels. The valuable data in Da.D.O. allowed significant improvements of the method than its original version. The model has been recently applied in the context of ReLUIS project, funded by the DPC to support the development of Italian Risk Maps. To this aim, the vulnerability model has been applied for deriving fragility curves. This step requires to introduce a correlation law between the Macroseismic Intensity (adopted for the calibration of the model from a wide set of real damage data) and the Peak Ground Acceleration (at present, one of most used instrumental intensity measures); this conversion further increases the potential of the macroseismic method. As presented in the paper, the first applications of the model have produced plausible and consistent results at national scale, both in terms of damage scenarios and total risk (economic loss, consequences to people).

Comparative analysis of the fragility curves for Italian residential masonry and RC buildings

“…Four out of the six fragility models refer to masonry buildings, and the remaining two to RC buildings. Among the masonry fragility models, one has a mechanical derivation (Donà et al 2020), one is based on an empirical-heuristic approach (Lagomarsino et al 2021) and the other two have an empirical derivation (Rosti et al 2020a;Zuccaro et al 2020). Regarding the models for RC buildings, one is developed on a mechanical basis (Borzi et al 2020b) and the other on an empirical basis (Rosti et al 2020b).…”

Towards the updated Italian seismic risk assessment: exposure and vulnerability modelling

“…In 2018, the seismic risk scenario for the National Risk Assessment (DPC 2018) was evaluated with the platform IRMA (Borzi et al 2020), by combining the ones obtained by using different vulnerability models (Rosti et al 2020a, b;Lagomarsino et al 2021;Donà et al 2020;Zuccaro et al 2020;Borzi et al 2020) and assigning to them the same weight (Dolce et al 2020).…”

“…The comparative analysis of fragility curves used in the 2018 risk assessment has shown (e.g. Rosti et al 2020a, b;Lagomarsino et al 2021) that the distance between the damage levels is well represented by the following law:…”

“…Vulnerability models have been proposed, mainly based on the empirical approach and considering the macroseismic intensity as intensity measure (Guerreiro et al 2000;da Porto et al 2012;Leite et al 2013;Sorrentino et al 2014;De Matteis et al 2016;Marotta et al 2018;Penna et al 2019;Lagomarsino et al 2019;Canuti et al 2019;Cescatti et al 2020). Fragility curves may be derived from these models, analogously to what was done for the residential buildings (Lagomarsino et al 2021). However, one of the aims of the WP2-MARS is to collect all the damage data observed on churches in the last 25 years in Italy, with survey form originally proposed after the Umbria-Marche earthquake (1997) and then formally adopted by the Civil Protection Department (G.U.…”

Guest editorial to the special issue—Seismic risk assessment in Italy

“…For the development of Vulnerability/Exposure Models for ordinary masonry buildings: Rosti et al (2020a) and Zuccaro et al (2020) adopt empirical approaches, Donà et al (2020) employ an analytical approach, while Lagomarsino et al (2021) use a hybrid (heuristic) methodology.…”