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The structural and seismic fragility assessment of minor historical centers of the Inner Peripheries of Italy is a key phase of the preservation process of the historical and cultural features of a portion of the Italian building stock, whose reuse is crucial for the reversal of shrinking trends and the stimulation of population growth. In this framework, the opportunities offered by digital crowd-sourcing technologies with respect to performing probabilistic structural safety assessment at a large scale are investigated herein. The objective of this research was to exploit data and information available on the web such that the key building features of an area of interest are collected through virtual inspections, historical databases, maps, urban plans, etc. Thus, homogeneous clusters of buildings identified in the area of interest are catalogued and associated with specific building classes (chosen among those available in the literature), and the buildings' levels of seismic fragility are determined through the development of fragility curves. The research outcomes show that the proposed approach provides a satisfactory initial screening of the seismic fragility level of an area, thus allowing for the identification of priority zones that require further investigations or structural interventions to mitigate seismic risk. [ABSTRACT FROM AUTHOR]

This paper focuses on seismic fragility and damage scenario assessment of minor Italian historical centres through the development of urban fragility curves. With reference to the case study of Balvano, a small centre located in Basilicata Region of Italy, two hybrid models have been adopted. The first is a mechanic-based hybrid model developed by the authors to derive urban fragility curves specifically; the second is the macroseismic method, originally conceived to derive typological fragility curves for single building classes, expanded to derive urban fragility curve herein. Balvano was strongly struck by 1980 Irpinia-Basilicata earthquake (Ms = 6.90) and hence subjected to an intense reconstruction process during 1980s, where almost the 80% of the buildings were reconstructed with reinforced concrete structures in the place of unreinforced masonry ones. Seismic vulnerability and damage scenarios before and after 1980 have been assessed and compared with the purpose of validating the effectiveness of the urban scale fragility curves obtained through hybrid methodologies and quantifying the effect of the 'new' seismic hazard maps and first seismic codes and recommendations released by the Italian Government in the aftermath of 1980 for the construction of new buildings or for retrofitting the existing ones. A good matching between predicted and occurred damage scenario from the research outcomes emerged, confirming the effectiveness of the urban scale hybrid fragility curves to assess seismic vulnerability at urban scale. Moreover, the comparison of the damage scenarios pre and post-reconstruction highlighted the crucial role played by the code prescriptions adopted in that years for reducing the seismic vulnerability of the municipality and the importance of the 'new' seismic hazard maps introduced in 1980s. Finally, the differences between mechanical-based hybrid and macroseismic model have been discussed in the paper. [ABSTRACT FROM AUTHOR]

This paper presents a novel hybrid-based methodology devoted to develop urban fragility curves and damage probability matrices to predict likelihood seismic damage scenarios for small and medium Italian urban centres, considering URM buildings only. The concept of urban fragility curve consists of a single curve mean-representative of the seismic fragility of an entire area accounting for the combinations of building classes and their percentage, then they differ from those typological. The methodology has been developed with reference to Rocca di Mezzo, a small Italian urban centre located in the central Apennine area, Italy. Based on CarTiS inventory, building classes have been firstly recognized and urban fragility curves, representative for damage scenarios at Ultimate Limit State, developed. To predict damage scenarios from low to high-intensity earthquakes, an approach to define multi-damage urban fragility curves and damage probability matrices has been also presented. To this aim, a damage scale suffered by building classes has been defined by converting the final outcomes of the AeDES form (used in Italy for post-earthquake surveys) in the damage levels provided by the European Macroseismic Scale (EMS98). Data coming from urban fragility curves have been compared with the actual damage scenario recorded in Rocca di Mezzo after the 2009 L'Aquila's earthquake, in terms of both peak-ground acceleration and Mecalli-Cancani-Sieberg scale. The achieved results showed a good accordance between theoretical predictions and actual damage scenarios, coherent also with the damage scenarios occurred in other Italian historical centres hit by severe earthquakes over the years. Thus, the methodology can provide a first important indicator to support the development of emergently plans devoted to identify priority of interventions in such areas particularly vulnerable with respect to others. [ABSTRACT FROM AUTHOR]

A hybrid seismic fragility model for territorial-scale seismic vulnerability assessment of masonry buildings is developed and presented in this paper. The method combines expert-judgment and mechanical approaches to derive typological fragility curves for Italian residential masonry building stock. The first classifies Italian masonry buildings in five different typological classes as function of age of construction, structural typology, and seismic behaviour and damaging of buildings observed following the most severe earthquakes occurred in Italy. The second, based on numerical analyses results conducted on building prototypes, provides all the parameters necessary for developing fragility functions. Peak-Ground Acceleration (PGA) at Ultimate Limit State attainable by each building's class has been chosen as an Intensity Measure to represent fragility curves: three types of curve have been developed, each referred to mean, maximum and minimum value of PGAs defined for each building class. To represent the expected damage scenario for increasing earthquake intensities, a correlation between PGAs and Mercalli-Cancani-Sieber macroseismic intensity scale has been used and the corresponding fragility curves developed. Results show that the proposed building's classes are representative of the Italian masonry building stock and that fragility curves are effective for predicting both seismic vulnerability and expected damage scenarios for seismic-prone areas. Finally, the fragility curves have been compared with empirical curves obtained through a macroseismic approach on Italian masonry buildings available in literature, underlining the differences between the methods. [ABSTRACT FROM AUTHOR]

Structural safety assessment of urbanised areas exposed to seismic risk is a complex task and can be approached at different scales. Fragility functions are the most effective tool to perform an estimation of the structural risk, since they describe the exceeding probability of the limit state of interest given a level of ground shaking. The formulation of a fragility function is based on the selection of an Intensity Measure of the ground shaking, commonly represented by peak-ground or spectral parameters or by macroseismic intensity grades. In the present paper, a novel approach to estimate the seismic vulnerability at a large scale of urbanised areas is presented. The scenario earthquakes are selected according to the current formulation of the seismic hazard disaggregation provided by National and International codes, i.e. through the disaggregation in terms of magnitude (M), epicentral distance (R) and number of standard deviation from the median ground motion (ε). To this aim, a vectorial seismic Intensity Measure is assumed to compute structural safety at large scale, and a change of variables is made to turn the traditional fragility curve into a matrix. Typological fragility matrices are processed and combined to define the so-called Urban Fragility Matrices, representative of the vulnerability of selected urban sectors. The procedure is then implemented and validated referring to the city of Pozzuoli (Southern Italy) and its effectiveness validated with reference to the damage survey relative to the 4th October 1983 seismic event which struck the city, resulting a good matching between predicted and observed scenarios. • A novel methodology for probabilistic safety assessment of buildings at large scale has been proposed. • Source-to-site disaggregation of ground motion has been taken into account used to define the seismic fragility. • A new tool, called urban fragility matrices, has been introduced to assess seismic fragility at large scale. • The proposed methodology has been validated with respect to the case study of Pozzuoli (southern Italy). [ABSTRACT FROM AUTHOR]

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