Seismic Vulnerability and Old Towns. A Cost-Based Programming Model (original) (raw)
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Seysmic Vulnerability and the Old Towns: A Cost-Based Programming Model
Vulnerability is the big issue of the small inland urban centers exposed to the risk of depopulation. In the climate and in the context of an increasing seismic risk in the center-northern part of Italy, seismic vulnerability can become the determinant cause of the final abandonment of a small town. In some Italian regions, as well as Emilia Romagna, municipalities are implementing seismic vulnerability reduction policies based on the Emergency Limit Condition that has become a basic reference for ordinary land planning. This study proposes a valuation planning approach to the seismic vulnerability reduction carried out within the general planning framework concerning the Faentina Union, a group of five small towns located in the south-western part of the Province of Ravenna, Italy. The approach consists of three main stages: knowledge – the typological, constructive and technological description of the buildings specifically concerning their vulnerability degree; interpretation – t...
Managing Emergency Into Historic Centres in Italy: Seismic Vulnerability Evaluation at Urban Scale
Proceedings of the 7th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2019
Italy is one of the most earthquake prone areas in Europe and one of the countries with the richest cultural legacy in the world. A series of seismic events occurred in the last decades caused considerable casualties and damage to historic centres, highlighting the need of undertaking protective measures to limit the impact of any potential earthquake. The complex morphology of historical city centres with their century-old built environment contribute to the high vulnerability and exposure in the areas. This research introduces an interdisciplinary approach to implement the seismic emergency management for historical centres in Italy and consequently to address their preventive planning. A procedure combining vulnerability analysis and urban spatial techniques allows defining a ranking of priority interventions to be included into a preventive plan in order to ensure free escape routes and clear access for the emergency services during the post-seismic phase. The first step of this work is the survey of the present-day configuration of historic centres, with their historical assets, aggregates, critical infrastructures, urban functions and strategic activities. Then, a key aspect regards the vulnerability assessment of the urban fabric in order to predict post-seismic damage scenarios. By considering the interference of the buildings' vulnerability with the street network, it is possible to develop mitigation strategies to improve the emergency management.
Bulletin of Earthquake Engineering, 2022
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.
Risk Analysis of Historic Urban Areas: A Case Study of the Salerno City, Italy
Journal of Civil Engineering and Architecture, 2015
The preservation of historical and cultural heritage from seismic risk is a question of interest in Italy. However, too little has been done to deal with this problem. First of all, the seismic safety of cultural heritage should be a topic of prevention. The research described in the paper presents a multi-approach procedure to address risk assessment of large-scale urban systems with the aim to contribute at the development of risk mitigation policies for historical centers buildings. The observation of the earthquakes effects in Italy clearly highlights the role of the high vulnerability of the existing building on the consequences in terms of casualties and damage, rather than the severity of seismic events, especially in historical contexts. Unlike the new buildings which should be planned and designed to respect seismic safety requirements, existing buildings require a careful safety assessment on the basis of their susceptibility to damage which depends on building techniques, past damage events, maintenance, changes, etc.
Engineering Structures, 2006
The prevailing Italian and Greek methodologies for seismic risk assessment are used herein to construct loss scenarios for the building stock of a small city (Potenza, Southern Italy). The inventory of buildings of interest is obtained from a survey carried out after the 1990 earthquake that struck Potenza and its hinterland, subsequently updated in 1999. About 12,000 buildings were surveyed in Potenza, using the Italian first level survey form for damage and vulnerability evaluation. In the Italian methodology, a hybrid technique is set up to evaluate vulnerability, combining an analysis of building typologies with expert judgement. The probabilistic distribution of damage is evaluated by assigning Damage Probability Matrices (DPMs) from the literature. Besides the vulnerability classes A, B and C of the MSK-scale, the class D of the anti-seismic buildings is considered and the relevant DPM is defined. Damage and economic loss scenarios relevant to dwelling buildings are constructed for three reference earthquakes. Next, the hybrid methodology for seismic vulnerability assessment of reinforced concrete (R/C) and masonry buildings developed at the University of Thessaloniki (Greece) is applied to the same building stock. The methodology combines available statistical data of damage collected after past earthquakes with a systematic nonlinear analysis of various "model buildings", representative of several vulnerability classes. Similarities, as well as discrepancies, between the two methods are discussed in the light of the obtained results, and possible sources for the discrepancies are suggested.
Influence of local site effects on seismic risk maps and ranking of Italian municipalities
Bulletin of Earthquake Engineering, 2023
The latest studies concerning seismic risk assessment in Italy were developed without considering the site geo-lithological effects, thus limiting the assessment to rock soil type. In this study, for the evaluation of site amplification effects, we used the results of recent works based on the Italian seismic microzonation data. As this first study is performed for the entire Italian territory at the municipality scale, the site amplification factors (AFs) have been assigned to the chief town of each of the 7715 Italian municipalities, assuming that the building stock is concentrated in that small area. The AFs have been compared with those foreseen by the Italian building code (NTC2018). The PGA amplification with the new AFs ranges from 1 to 2.2 bringing to an average increase of 75% in the hazard, compared to 27% if using the NTC2018 amplification. The seismic risk has been evaluated using the probabilistic hazard assessment adopted in the NTC2018 and recent vulnerability/exposure models developed for Italy. The residential building stock was subdivided into 5 vulnerability classes (3 for masonry and 2 for concrete) derived from the national census data and further refined using the construction age and building height. The results show that, for a rock site condition, the loss estimates are comparable with those of previous works in terms of casualties, homeless, and economic damage. The introduction of the site effects brings to a significant increase in the expected losses resulting higher than the historical data retrieved from a careful analysis of the major Italian earthquakes. This suggests the importance of developing new fragility curves based on updated AFs. To support the implementation of risk reduction programs, a seismic risk index is introduced, allowing a municipality ranking by risk, a cost estimation of the seismic retrofitting in the highest risk municipalities, and an assessment of the consequent risk reduction.
Earthquake Resistant Engineering Structures IX, 2013
The quantitative measure of seismic vulnerability is a necessary requirement for prevention and for an optimal emergency management. Before L'Aquila's earthquake in 2009, the National Civil Protection, in collaboration with the University of L'Aquila, developed a model (Beolchini, "Definition of an indicator of urban vulnerability" (2003)) to evaluate the criticality seismic of urban centers by using a multidisciplinary approach. The study has led to the definition of an urban vulnerability index, that allows to identify the most critical urban centers and the problematic elements, in order to establish a hierarchy for preventative measures and for an efficient emergency management (Calvi et al. "Development of seismic vulnerability assessment methodologies over the past 30 years" (2006). One of the features of this evaluation is that it allows a simultaneous analysis of the multiple factors involved in risk assessment (Ferlito and Pizza "Modello di vulnerabilità di un centro urbano. Metodologia per la valutazione speditiva della vulnerabilità della viabilità d'emergenza" (2011); Ferlito et al. "Danger treblement de terre et mesure du risque à L'Aquila" (2010)). After the seismic event occurred, same tests have been done to verify the validity of the model on the part of buildings, by comparing the criticality evaluated and damage suffered by the buildings, taking into account the local effects resulting from operations of microzonation. The seismic vulnerability
Engineering Structures, 2017
The paper presents a predictive model for assessing the seismic vulnerability of small historic centres. The model, developed in the framing of other similar methods proposed in the past, needs a limited number of parameters and is based on information collected in the aftermath of the 2009 L'Aquila earthquake. First, a damage survey carried out on two historic centres hit by L'Aquila earthquake is presented and the most recurrent failure types are classified in terms of severity and extension, leading to damage probability matrices (DPMs). Second, the proposed predictive model is calibrated on the basis of simple observations on the buildings' structural features. Finally, the model is validated through the application to a third historic centre characterized by the same features of the first two case studies. This application proves the generality of the proposed procedure by accurately reproducing the damage that was actually reported after the 2009 earthquake. The model provides useful information on the most effective anti-seismic strategies that could be implemented at the urban scale for seismic risk reduction.
International Journal of Disaster Risk Reduction, 2019
This work proposes a framework for the development of seismic risk maps at the nationwide scale. The seismic risk map is computed taking into account a seismogenic model of the analyzed area, and properly characterizing vulnerability and exposure of an asset of interest. A risk-targeted indicator named Municipal Expected Annual Loss (MEAL) is introduced and used as suitable metric for the development of the map, and for the subsequent seismic risk rating. The framework is then applied to show its usefulness in order to derive the seismic risk map of Italy considering the residential building stock as asset of interest. The proposed scientific approach for mapping seismic risk can be further used to develop a seismic risk reduction program and then evaluating its financial sustainability. The final part of the paper shows therefore a hypothetical seismic risk reduction program for the Italian residential building stock, estimating costs, benefits, and time-intervals required to guarantee its financial sustainability with the introduction of different taxation scenarios.
Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2021
Italy is a country with high seismic risk; however, a broad seismic classification of the national territory has been introduced only in the last twenty years. Therefore, most of the existing buildings stock do not comply with the current anti-seismic codes. In recent years, the seismic events that occurred in Italy have highlighted the complexity of emergency management and the great challenge for public authorities called to answer to the post-event reconstruction and the planning of effective risk prevention and mitigation measures implemented in "peacetime". In this perspective, the CAESAR II project (Controlling, Mitigating and Managing Earthquake Emergency: Cost-Benefit and Multi-criteria Analysis of Impact Scenarios for Risk Reduction and Increased Resilience) has been developed as a decision support system for public authorities engaged in the development of seismic disaster risk reduction plans. CAESAR II includes a module for the simulation of retrofitting measures applied at the municipal scale, integrating different categories of anti-seismic and energy improvement measures based on the vulnerability analysis of the existing buildings stock. The CAESAR II tool's core is the module for evaluating "seismic impact scenarios" based on the end-users' hazard. The output of the model includes information on expected damage levels for buildings (from D0-no damage to D5-total collapse) and population (dead, injured and homeless). Impact scenarios can be customised according to the minimum unit of analysis assumed (municipality or 250x250m square mesh grid) and the availability of exposure data (from national census data or survey on the spot building by building according to the PLINIVS form). Scenarios include geo-referenced data managed by geo-servers to exchange data in a format compliant with OGC (Open Gis Consortium) standards and the European INSPIRE Directive. Simulation results can be further processed through the Multi-Criteria and Cost-Benefit Analysis modules to support the comparative assessment of alternative seismic and energy measurements. In this work, the procedures included in CAESAR II are described and a case study is reported. It concerns the analysis of the expected damage assessment on buildings and population for three municipalities in northern Italy,