SEISMIC VULNERABILITY ASSESSMENT OF HISTORICAL URBAN CENTRES: THE CASE STUDY OF CAMPI ALTO DI NORCIA, ITALY

Abstract. Seismic damage assessment is a valuable opportunity to evaluate the accuracy of vulnerability and risk methodologies applied to historic masonry buildings, giving the possibility of enhancing and optimizing mitigation and retrofit strategies. Vulnerability index methodologies are flexible and powerful tools for the seismic assessment at urban scale, able to provide a first screening of the critical issues present in masonry structural aggregates. The different structural features of the buildings, directly and indirectly influencing their structural behaviour, are measured through different weights and scores finally achieving a vulnerability indicator. In the present paper, four different vulnerability index methodologies are applied to the medieval city of Campi Alto di Norcia in Valnerina, Umbria, recently stroke by the 2016 Central Italy earthquakes. The accuracy of the adopted Iv methods is assessed based on the real damages' analysis performed in the surrounding area, comparing results achieved from the application of considered methodologies to direct in-situ observations. Data collected during the 2016 post-earthquake damage surveys and usability assessment, together with the external visual inspections carried out and with the information coming from retrofitting design interventions performed between 1979 and 1997, are used

Seismic vulnerability assessment of historical urban centres: The case study of campi alto di norcia, Italy

Seismic damage assessment is a valuable opportunity to evaluate the accuracy of vulnerability and risk methodologies applied to historic masonry buildings, giving the possibility of enhancing and optimizing mitigation and retrofit strategies. Vulnerability index methodologies are flexible and powerful tools for the seismic assessment at urban scale, able to provide a first screening of the critical issues present in masonry structural aggregates. The different structural features of the buildings, directly and indirectly influencing their structural behaviour, are measured through different weights and scores finally achieving a vulnerability indicator. In the present paper, four different vulnerability index methodologies are applied to the medieval city of Campi Alto di Norcia in Valnerina, Umbria, recently stroke by the 2016 Central Italy earthquakes. The accuracy of the adopted Iv methods is assessed based on the real damages' analysis performed in the surrounding area, comparing results achieved from the application of considered methodologies to direct in-situ observations. Data collected during the 2016 post-earthquake damage surveys and usability assessment, together with the external visual inspections carried out and with the information coming from retrofitting design interventions performed between 1979 and 1997, are used

Evaluation of mechanical characteristics of steel bars by nondestructive Vickers micro-hardness tests

Materials’ properties evaluation represents a crucial aspect for the static and seismic assessment of existing Reinforced Concrete (RC) structures and infrastructures. While concrete's mechanical characteristics are classically investigated by both destructive tests (DTs) and non-destructive tests (NDTs), for steel reinforcing bars the use of NDTs is not consolidated: a large number of samplings are planned as part of the survey campaign, requiring strong effort to be both extracted and restored and being, moreover, not always sufficient to reliably determine the characteristics of each type of steel grade/rebar used in the structure. Within NTDs, the determination of the hardness value could be a viable way to estimate rebars’ tensile strength. Many experimental studies were proposed in the past and current scientific literature, most of them performed through laboratory tests and therefore requiring a strong time and economic effort: the adoption of portable instruments for the determination of the in-situ hardness of rebars can be a good possibility to reduce the impact on the structure/infrastructure and to optimize timing and restoration operations. Of course, the methodology adopted shall be opportunely calibrated and attention shall be paid to the interpretation of the achieved data. The present research work aims at testing the effectiveness of NDT Vickers micro-hardness tests in the estimation of the mechanical properties of steel reinforcing bars. A methodology is proposed to achieve reliable correlations between hardness values and tensile strength of rebars, accounting for parameters affecting in-situ measures and different typologies of steel grades/rebars

Steel-based applications in earthquake-prone areas

Steel-Earth project aims at distributing among technicians, engineers, design companies and standardization bodies the results of three past RFCS projects (Steel-Retro [3], Opus [2] and PrecaSteel [1]), providing useful tools for the design and for the retrofit of existing buildings. Technical documents and practical applications to case studies, regarding design of steel and composite steel/concrete buildings and innovative steel-based techniques for the retrofit of existing r.c. and masonry constructions, have been elaborated and collected into a volume distributed during the final workshop of the dissemination project. Pre-normative and background documents concerning the design of steel and composite structures and the rehabilitation of existing constructions have been prepared. A lot of attention has been paid to the analysis of the influence of overstrength factors on the seismic design of steel and composite structures. The prepared documents have been distributed to the attending people and to the members of WG 2 (CEN/TC 250/SC 8/WG 2 “Steel and Composite Structures”) during the final workshop of the project. Technical sheets, working examples and background documents have been translated into several languages (German, French, Italian, Romanian and Greek) and are free available on the website of the project (https://www.steelconstruct.com/site/), where information regarding Steel-Earth are also presented.11 Workshops in Italy, Greece, Germany, Belgium, Portugal, Spain and Romania and 5 conferences in Emilia-Romagna have been organized, as well as 2 practical courses for engineers and academic people in Pavia (Italy). Flash-drives with the technical documents and applications elaborated in Steel-Earth have been distributed to the attending people

Structured cost analysis of robotic TME resection for rectal cancer:a comparison between the da Vinci Si and Xi in a single surgeon's experience

Background: Robotic-assisted surgery by the da Vinci Si appears to benefit rectal cancer surgery in selected patients, but still has some limitations, one of which is its high costs. Preliminary studies have indicated that the use of the new da Vinci Xi provides some added advantages, but their impact on cost is unknown. The aim of the present study is to compare surgical outcomes and costs of rectal cancer resection by the two platforms, in a single surgeon’s experience. Methods: From April 2010 to April 2017, 90 robotic rectal resections were performed, with either the da Vinci Si (Si-RobTME) or the da Vinci Xi (Xi-RobTME). Based on CUSUM analysis, two comparable groups of 40 consecutive Si-RobTME and 40 consecutive Xi-RobTME were obtained from the prospectively collected database and used for the present retrospective comparative study. Data costs were analysed based on the level of experience on the proficiency–gain curve (p–g curve) by the surgeon with each platform. Results: In both groups, two homogeneous phases of the p–g curve were identified: Si1 and Xi1: cases 1–19, Si2 and Xi2: cases 20–40. A significantly higher number of full RAS operations were achieved in the Xi-RobTME group (p < 0.001). A statistically significant reduction in operating time (OT) during Si2 and Xi2 phase was observed (p < 0.001), accompanied by reduced overall variable costs (OVC), personnel costs (PC) and consumable costs (CC) (p < 0.001). All costs were lower in the Xi2 phase compared to Si2 phase: OT 265 versus 290 min (p = 0.052); OVC 7983 versus 10231.9 (p = 0.009); PC 1151.6 versus 1260.2 (p = 0.052), CC 3464.4 versus 3869.7 (p < 0.001). Conclusions: Our experience confirms a significant reduction of costs with increasing surgeon’s experience with both platforms. However, the economic gain was higher with the Xi with shorter OT, reduced PC and CC, in addition to a significantly larger number of cases performed by the fully robotic approach

Seismic Assessment of Historical Masonry Buildings at Different Scale Levels: A Review

The relevant losses determined by recent earthquakes stressed the vulnerability of historical masonry constructions towards horizontal seismic actions, therefore highlighting the need for reliable approaches for the structural assessment and following retrofit. During the last decades, the scientific community has widely investigated the tools to analyse the performance of such structural typologies, resulting in a multitude of different methodologies depending on the building’s features and the goal of the analysis. The task is particularly challenging because of the frequently limited knowledge concerning the state of the art and the high structural complexity due to overlapped construction phases. A general literature review of the methods adopted for the structural assessment of historical masonry buildings is proposed in the present paper. The methods are grouped according to the operational scale, providing an overview of the current state of the art

Structural and economical performance of reinforced concrete frames with Dual-Phase and TempCore® steel rebars in uncorroded and corroded conditions

In the last decades, the need to develop new enhanced typologies of steel reinforcement bars with improved ductility and durability performance in presence of aggressive environmental conditions progressively increased due to the negative consequences that corrosion showed on the structural capacity of reinforced concrete (RC) buildings. Within the recently concluded NEWREBAR research project, a new reinforcing steel grade with Dual-Phase (DP) microstructure and selected low-carbon content chemical composition (kept in the range of the actual European production) was developed, produced, and tested even in presence of accelerated induced corrosion. To understand the impact of the adoption of DP rebars in RC structures, case study buildings were designed, modeled, and analyzed using the new grade and compared to traditional buildings using TempCore® rebars. In the present work, the results of a techno-economic analysis performed on both DP and TempCore® RC buildings through the evaluation of the expected annual loss (EAL) index is presented for a residential five-storeys case-study building, assessing the benefit introduced by adopting the proposed new reinforcing grade even in presence of corrosion

Use of high-strength steel for multi-criteria optimization of dissipative devices

Among the various strategies for the seismic protection of buildings, the use of passive devices based on energy dissipation through the development of plastic deformations represents a valid, simple and economic solution. During seismic events, damage is concentrated in correspondence of the dissipative elements which are thought to be replaced in the post-seismic phase in order to fully recover the initial capacity of the device and, therefore, to restore the original building behaviour. In this context, the adoption of steel devices has relevant impact and advantages on the overall building performance. In the present study, the implementation of a steel dissipative and replaceable device using High-Strength Steels (HSS) for the non-dissipative components was deeply analyzed, and results are briefly presented. The improvement due to HSS adoption accounted for the direct/short-term economic aspects (i.e. cost of the device, weight) and the indirect/long-term ones (i.e. seismic risk performance) within a multi-criterial optimization procedure

Seismic performance of an innovative dissipative replaceable components bracing steel frame (DRBrC)

The structural performance of a steel Concentrically Braced Frame (CBF) equipped with replaceable dissipative seismic components, called DRBrC, is presented. X-diagonal CBFs are an efficient structural solution for buildings in seismic prone areas, being conceived to dissipate the energy stored during the earthquake through plastic deformation of bracing elements; all the other components remain in the elastic field thanks to opportune design criteria. Of course, structural damages, even if voluntarily located in specific regions, need to be repaired after the seismic event to restore the functionality of the building, leading to relevant economic (and time) effort since the full replacement of damaged dissipative components is necessary after irreversible plastic deformations. Recently, research activities have been widely carried out to provide repairability of steel buildings by means of easily replaceable dissipative components. The Research Fund for Coal and Steel (RFCS) of European Commission, for instance, promoted and funded the research project DISSIPABLE - Fully dissipative and easily reparable device for resilient buildings with composite steel-concrete structure”, with the aim of designing, producing, optimizing and testing several dissipative components for steel structures having, as fundamental feature, the full repairability after the earthquake without impacting on other components. In the present paper, the seismic performance of a steel braced frame equipped with a specific typology of dissipative replaceable device at the ends of braces is presented by means of nonlinear analyses