Sabrina Taffarel

A Bayesian approach to rapid seismic vulnerability assessment at urban scale

ABSTRACT The seismic vulnerability of city centers is commonly assessed by extending the study methods applied to single buildings to urban aggregations. This approach is not always applicable at territorial scale, as it is uneconomical in terms of time and costs. An innovative method provides reasonable large-scale a priori estimation of parameters not directly evaluable from the exterior of buildings by elaborating values which can be measured from the outside. Those parameters are treated as continuous variables, by assigning them a suitable probability density function. The Bayesian approach is adopted, which allows the update of initial hypotheses by using new data gathered during on-site surveys. In this regard, a rapid survey form for the on-site data collection is proposed. An example of its application to a façade of a building structural unit in Santo Stefano di Sessanio in L’Aquila province (Italy) is proposed, showing promising preliminary results for buildings belonging to Italian historical centers.

Comparing expeditious procedures for the seismic vulnerability assessment on the European territorial context: reliability, feasibility, cost, and time consumption

ABSTRACT The definition of strategies for the preservation and protection of cultural heritage is a topical issue, especially in view of the increasing relevance of the theme of seismic risk mitigation and reduction. The prediction of the impact an earthquake could have on existing buildings requires the knowledge of their dynamic behaviour. The procedure to be adopted for this purpose is quite complex and onerous in terms of costs, time, and implementation, especially when the study concerns territorial areas rather than single buildings. The definition of methodologies aimed at respecting the principles of economic sustainability and preserving human life and architectural heritage is of paramount importance to assess seismic vulnerability using available resources. Rapid methods for the seismic vulnerability assessment, aimed at defining buildings vulnerability and intervention priority lists, must be implemented to guarantee the preservation of historical centers. This article describes the application to some case studies of different methods aimed at creating fragility curves for the vulnerability assessment on the European territorial context. The comparison between a deterministic approach and a new probabilistic one is performed for all case studies, to define the most suitable methodology in terms of reliability and savings in cost and time.

Structural Investigations and Modelling of Seismic Behaviour on Ruins in the Monumental Area of Hierapolis of Phrygia

The archaeological site of Hierapolis of Phrygia presents a number of ruins, which date back to the II century B.C. They are located in a medium-high seismic area crossed by a system of faults still active. The valorisation plan of the site aims at establishing an archaeo-seismological area, i.e., a site where tourists can visit structures keeping the signs of past earthquakes in proper safety conditions. To this purpose, the knowledge phase is a fundamental step in the preservation process. The paper presents the results of a series of investigation procedures applied to several incomplete structures still standing in the area, namely: the Martyrion of St. Philip, the tombs A18 and A20, and the monumental latrines. The geometrical survey and the elaboration of images were used in combination, as base for the evaluation of the conservation conditions, the interventions applied in the past, and the deterioration and damage states of the structures. To integrate the analysis, soil and structures were also inspected on site with NDT procedures. In particular, tests provided the seismic soil classification (by MASW, HVSR) and the qualification of masonry elements (by SPVT, GPR). Limit analysis and FEM approach were adopted to characterize the actual seismic behaviour of the structural assemblages and to predict their possible future damage. Results pointed out the high vulnerability of large portions of the structures still standing in the site.

Seismic vulnerability maps of Timisoara historical center based on fragility curves

The seismic vulnerability assessment on a territorial scale requires the application of simplified procedures. Data collection is usually carried out by adopting external inspections; for this reason the knowledge gained for the considered buildings is usually not complete and lack of information has to be managed. The definition of a methodology which takes into account these aspects is one of the aims of this paper. Another goal is the extension of the obtained results to buildings not directly surveyed on site, whose characteristics are similar to those of the analyzed buildings. The case study of Timisoara (Romania) is presented. A rapid survey of the historical center is performed and recurring typologies are identified. Analyses of the most significant local mechanisms of collapse are implemented, taking into account possible parameters variation. Fragility curves for each typology are then obtained allowing the definition of vulnerability maps for the whole historical center. 2 DESCRIPTION OF TIMISOARA CASE STUDY 2.1 A general urbanistic overview of the analyzed area Timisoara is the main town of Timis County and is considered the informal capital city of the historical region of Banat, in western Romania. The first documentation about the city organization dates back to the XII century, when Timisoara belonged to the Kingdom of Hungary. In 1718, under the Habsburg domination, Timisoara became the capital city of Banat and Prince Eugene of Savoy issued a “Building Regulation” for the town, ordering the demolition of all existing buildings and their new organization within a rectangular street network; compulsorily buildings had to be reconstructed using bricks. The majority of analyzed blocks are located in the historic city center, the so called district of Cetate. Another analyzed area is Iosefin district, located at south-west of the city. The XVIII century urban plan still rules current city configuration. Buildings dated in the first half of the century occupy the inner part of the center, while constructions belonging to the period between the half of the XVIII century and the half of the XIX century occupy suburban spaces located inside old fortifications. During the 1848-1849 Revolution, many buildings where partially destroyed by bombing, so between the end of the XIX century and the beginning of the XX century many constructions were rebuilt, often conserving not destroyed ground floors and rebuilding upper floors. The district of Iosefin developed at the end of the XVIII century as an answer to the lack of space in the city center. Analyzed blocks are dated to the second half of the XIX century (Figure 1). Figure 1. Identification of analyzed areas: Cetate district (on the right) and Iosefin district (on the left).