Multi-risk assessment in a historical city Arrighi, C.; Tanganelli, M.; Cristofaro, M. T. ...
Natural hazards (Dordrecht),
11/2023, Letnik:
119, Številka:
2
Journal Article
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Natural hazards pose a significant threat to historical cities which have an authentic and universal value for mankind. This study aims at codifying a multi-risk workflow for seismic and flood ...hazards, for site-scale applications in historical cities, which provides the Average Annual Loss for buildings within a coherent multi-exposure and multi-vulnerability framework. The proposed methodology includes a multi-risk correlation and joint probability analysis to identify the role of urban development in re-shaping risk components in historical contexts. The workflow is unified by exposure modelling which adopts the same assumptions and parameters. Seismic vulnerability is modelled through an empirical approach by assigning to each building a vulnerability value depending on the European Macroseismic Scale (EMS-98) and modifiers available in literature. Flood vulnerability is modelled by means of stage-damage curves developed for the study area and validated against ex-post damage claims. The method is applied to the city centre of Florence (Italy) listed as UNESCO World Heritage site since 1982. Direct multi-hazard, multi-vulnerability losses are modelled for four probabilistic scenarios. A multi-risk of 3.15 M€/year is estimated for the current situation. In case of adoption of local mitigation measures like floodproofing of basements and installation of steel tie rods, multi-risk reduces to 1.55 M€/yr. The analysis of multi-risk correlation and joint probability distribution shows that the historical evolution of the city centre, from the roman castrum followed by rebuilding in the Middle Ages, the late XIX century and the post WWII, has significantly affected multi-risk in the area. Three identified portions of the study area with a different multi-risk spatial probability distribution highlight that the urban development of the historical city influenced the flood hazard and the seismic vulnerability. The presented multi-risk workflow could be applied to other historical cities and further extended to other natural hazards.
The seismic vulnerability of masonry building aggregates is very difficult to determine, since it is affected by many uncertainties. The most uncertain quantities concern the historical periodization ...of structural aggregates. Moreover, the studies made at the urban scale can hardly be thorough, and usually the knowledge achieved on the single units is not fully satisfactory, so that the structural designer has to deal with uncompleted architectonical surveys and partial data; one of the most important problems concerns the lack of knowledge about the boundary conditions between adjacent structures. In order to perform mechanical analyses, an extensive knowledge of materials and techniques adopted is required. In this paper, an integrated methodology for the seismic assessment of building aggregate is presented. It concerns a multidisciplinary knowledge-based approach calibrated over the historical centres and the urban aggregates; the procedure joins different aspects, such as the use of modern technologies for an integrated knowledge, plans reconstructions through archival documents, laser scanner digital survey of urban fronts, non-destructive investigations of the materials. GIS and BIM platforms have been used to implement and collect data in order to perform detailed analyses. The information allowed to assess the seismic vulnerability of the building aggregates and the expected damage scenarios through empirical methodologies. The city of Scarperia, founded a few kilometres from Florence during the Medieval Age and characterized by a medium seismicity, has been chosen as a case study for the presented procedure.
•A random fc domain has been simulated on the base of a large experimental campaign.•Two alternative in-plan fc distribution models have been assumed to model a 3D case-study.•The effect of fc ...variability in terms of seismic demand and seismic performance have been evaluated.•The effectiveness of Eurocode 8 has been checked.•An extended interpretation of EC8 has been suggested.
Mechanical properties of concrete can consistently affect the seismic performance of RC buildings. A proper determination of the concrete strength is therefore essential for a reliable modeling of the structure. The current European Technical Code, Eurocode 8, provides a criterion for the strength assumption related to the knowledge level of the structure, which does not take into account the variability of the strength. If the concrete strength is affected by a large variability, the conventional strength value suggested by Eurocode 8 can be not conservative, since it does not consider the possible torsional effects due to a not homogeneous strength distribution and the reduced capacity of the weaker members.
In this paper the effects of the concrete strength variability on the seismic performance are investigated with a case study, that is a 4-storeys 3D framed building. The seismic response of the case study by assuming different amounts of strength variability has been compared with the Eurocode 8 previsions, both in terms of possible torsional effects and seismic performance.
A proper characterization of concrete strength is essential to correctly model existing RC structures, whose seismic performance is affected by the poor quality of materials. The purpose of this work ...is to evaluate the effect of incorrect assumptions for concrete strength and the adequacy of current Codes provisions (Eurocodes, FEMA). Even the effects of the non homogeneity of concrete strength within the building is considered due to its high variability; in fact, buildings can experience an irregular seismic response, both in plan and in elevation. In this work the effects of irregularity in plan due to the strength variability of concrete is analyzed on a case study, a four storey RC framed building, designed for vertical loads only. The variability of concrete strength has been evaluated using the data of an extensive investigation developed by REGIONE TOSCANA on a large sample of RC framed buildings.
A proper assumption of the concrete strength is essential to model existing RC structures; their seismic performance, in fact, can be affected by the poor quality of materials, both in terms of low ...strength and high variability. This paper considers the effects of the variability of concrete strength within buildings. Due to the high variability of concrete strength, in fact, buildings can experience irregular seismic responses, both in plan and in elevation. This research investigates the effects of irregularity in elevation due to the strength variability of concrete in a case study, namely a four-storey RC framed building, designed for vertical loads only. The variability of the concrete strength has been evaluated on the basis of an extensive survey carried out by the REGIONE TOSCANA (Tuscany Regional Government) on a large sample of RC framed buildings. Special attention has been paid to the adequacy of current codes provisions (Eurocodes, FEMA) on how to quantify concrete strength.
⢠KEY MESSAGE : The recommendations accompanying pesticide derogations from the FSC are not efficient for the management of leaf-cutting ants and termites in certified forest plantations in Brazil ...compared with chemical control using insecticides. FSC recommendations ignore the biological and ecological features of pests and forest plantations in Brazil when they set global rules for forest certification.
Earthquakes represent huge risks for cultural heritage. Although there is a large literature about prevention on historical buildings, the seismic assessment on collections and exhibition designs is ...usually underestimated. "RESIMUS" long running project involves different knowledge and fields; its goal is to prevent seismic damages to museum collections and artefacts, combining both museographical solutions and anti-seismic methods. This contribution focuses on the "Fontana di Giunone", designed in 1555 by Bartolomeo Ammannati and currently kept at the Museo Nazionale del Bargello. The museographical and historical researches have been combined with the seismic performance of the reconstructed Fountain. In this paper the first results provided by the seismic analysis of this artefact are shown. A 3D structural model has been set, based on the three dimensional digital model provided by an detailed laser scanner survey. An elastic dynamic analysis has been performed, by representing the seismic input through an ensemble of seven ground motions expressing the seismic hazard of the area. The analysis has provided the seismic response of the sculptures, evidencing its sensitivity to the dynamic properties of the considered ground motions.
It is well known that the axial load plays an important role in the evaluation of the structural capacity of RC columns. In existing buildings this problem can be even more significant than in new ...ones, since the material can easily present poor mechanical properties. The paper is aimed at the investigation of the role of the axial load variation on the seismic performance of RC columns of a case-study, i.e. a doubly symmetric 4-storey RC building. The effects of the axial load variation have been checked on the first storey columns, by comparing the seismic response, measured in terms of chord rotation and shear force, with the corresponding capacity. The sensitivity of the seismic performance to the axial load is evaluated with special attention on the type of analysis adopted to determine the seismic response and on considering a wide range of values for the concrete strength. The study points out a non-negligible effect of the axial load variation on the seismic response of the case-study building, especially when combined to concrete strength variability.
The seismic assessment of existing buildings is an essential issue of seismic engineering. This work is focused on the evaluation of the seismic performance of existing RC buildings according to the ...current Italian Technical Code, which almost coincides with the European Eurocode 8. Alternative types of analyses, all consistent to the Code provisions, have been performed with reference to a case-study, that is a real RC hospital building. An accurate knowledge of the building has been achieved, as a result of a collaboration between the University of Florence and the Regional Government. Both elastic and inelastic modeling, as well as static and dynamic ones, have been adopted in the analysis. The global response—with special attention to torsional effects—and the seismic performance of each single member have been found with all the performed analyses. The comparison among the analyses has been performed in terms of both global and local response parameters, and the reliability of each analysis has been pointed out.
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