The heuristic vulnerability model: fragility curves for masonry buildings

AbstractIn 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)

A seismic loss assessment procedure for masonry buildings

The paper provides a contribution for the assessment of economic losses in masonry buildings, following a component-based approach, to be implemented within the modern probabilistic seismic risk analysis. It is based on the computation of proper decision variables as the potential economic losses due to the direct repair cost, in order to improve the resilience to a seismic event. An application to a three-story unreinforced masonry building is illustrated, focusing on the computation of structural losses. Nonlinear dynamic analyses have been adopted, following the multiple stripe analysis method

Buildings Behaviour in Urban Fabric: The Safety Assessment Issue in the Post Earthquake Reconstruction Plans

This paper is the second one of two companion papers [1] that deal with the experience carried out in the post-seismic reconstruction plans activity in the Abruzzo region done by the research groups of the University of Catania (Coord. C.F.Carocci) and University of Genoa (S. Lagomarsino). In particular, this paper focuses on the issues related to the choice and use of the most suitable modeling strategies and analysis methods to perform the seismic assessment at scale of buildings in aggregate. Both recurring seismic responses of masonry, that is the global one and the local mechanisms, are considered. The strong complementarity with the knowledge phase, faced in detail in [1], is discussed by illustrating an application based on the use of an analytical mechanical model for the in-plane response and that of Macro Block model for the out-of-plane response

Earthquake damage assessment of masonry churches: proposal for rapid and detailed forms and derivation of empirical vulnerability curves

The post-earthquake damage assessment represents the first step after an emergency to support not only the safety of people, but also the preservation of buildings through the realization of prompt and effective provisional interventions. The issue is of particular relevance in case of monumental assets such as churches that are the focus of the paper. In Italy, since 1997 the post-earthquake damage assessment of churches has been carried out using a specific form, which was formally approved in 2001 by the Italian Civil Protection. Being the most advanced tool available in the literature within this specific field, the Italian form has been widely used also internationally. It follows the approach based on the decomposition of the church into macroelements. Although the latter has found wide confirmation through the interpretation of real damage, some critical issues were raised in relation to the versatility of the form and the reliability of the damage index that the approach provides. The post-earthquake damage assessment of 48 unreinforced masonry churches located in New Zealand, hit by the Canterbury earthquake sequence 2010\u20132011, represented an unprecedented opportunity, at international level, to investigate and to address the aforementioned issues. Starting from some weaknesses of the actual form, a new proposal (named CAF-D) for the damage assessment of unreinforced masonry churches has been developed and presented in the paper. The new form is still based on the macroelement approach, but it considers, in a separate way, the macroelements and the seismic damage modes they might develop, thus overcoming the limitation of the fixed number of damage mechanisms identified a priori by the current Italian form. The more reliable damage assessment approach that such form aims to achieve is the prelude to the development of a specific vulnerability model, derived by combining an empirical and an expert elicitation approach. A specific vulnerability model developed for New Zealand churches, derived by implementing the proposed CAF-D form and the related damage assessment procedure, is presented in the last part of the paper

Integration of Modelling Approaches for the Seismic Assessment of Complex URM Buildings: The Podestà Palace in Mantua, Italy

This study investigated seismic assessments of the Podestà Palace in Mantua (Italy). This masonry palace has a complex geometrical configuration that resulted from the addition of various units stratified over centuries. This feature makes seismic assessment challenging from a modelling perspective due to the interaction among units. Here, an integrated use of three modelling strategies characterised by a different computational effort and degree of accuracy was employed: (i) the Structural Element Model, according to the Equivalent Frame Approach, to study the global response of the whole structure and to estimate the mutual dynamic interactions among units; (ii) the Macro-Block Model, to assess the out-of-plane response of facades prone to the activation of local mechanisms; and (iii) the Finite Element Model, to deepen the seismic response of some critical parts, highlighted by a global analysis but also roughly described by the Equivalent Frame Model. This integrated approach consists in the use of results achieved from one modelling approach as input for another. For example, the floor spectra estimated by (i) were used to define the seismic input in (ii); for assessing the most critical portions, more accurate models were addressed (as in case (iii)). The comprehensive interpretation of the seismic behaviour obtained by these models also allowed us to address more rationally possible strengthening solutions, such as the in-plane stiffening of vaults (particularly spread in the building), aimed to guarantee a better redistribution of seismic actions in such a complex building

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

Within the 2019–2021 research agreement between the Civil Protection Department (DPC) and the Network of University Laboratories for Earthquake Engineering (ReLUIS), the work package WP4 “Seismic Risk Maps—MARS” is specifically devoted to update the 2018 release of the Italian National Seismic Risk Assessment. To this end, the previously considered models of hazard, exposure and vulnerability will be critically reviewed and updated by taking advantage also from the results deriving from other WPs of the DPC-ReLUIS research project. In the present paper some of the most relevant aspects that are being introduced in the development of the new Italian risk maps have been described and shortly analysed. First, a significant upgrade of the vulnerability model implemented in the new version of the platform used for risk calculation (IRMA) is proposed, where reference to the six EMS-98 classes is made also considering regional vulnerability features. Further, empirical data from observed real damage are integrated with results from numerical simulations (mechanical approach), in particular for reinforced concrete buildings. Finally, some special construction types such as schools, churches and bridges are included in order to provide a more comprehensive view of the national risk