Littérature scientifique sur le sujet « Seismic Risk in Monumental Buildings (RISEM) »

Monitoring seismic structural response is an essential issue in earthquake risk assessments and mitigation studies for monumental buildings in order to undertake earthquake disaster management. This study aims at identifying the resonant frequency of soil and modern and historical buildings in three major municipalities of Crete (Heraklion, Chania, and Rethymno) using ambient noise recordings (microtremors) considering the importance of soil–structure interaction to seismic structural response, particularly for historical buildings and monumental structures. In this study, ambient noise recordings have been processed through Horizontal to Vertical Spectral Ratios (H/V) to preliminarily examine the main frequencies and to examine whether the building has its main frequency close to that of the soil in order to identify potential resonance phenomena. Numerous ambient noise recordings were recorded on the soil, in the basement, and at each n-floor of the buildings. The incorporation of local site conditions and soil-building resonance phenomena into the urban planning development of Crete regarding earthquake risk assessments is necessary. In this direction, microtremors can be used as an effective tool to support civil protection preparation and operational decision-making in terms of earthquake disaster, specifically in the area of Crete, which is characterized by high seismic activity and a high cultural monuments capacity.

Masonry structures began to be built with the existence of human beings and are an inspiration for today’s structures. Monumental historical buildings built according to people’s religious beliefs have special importance among such structures. Despite being exposed to many natural disasters over time, such structures that have survived till today are an indispensable part of the historical heritage. Within the scope of this study, structural analyses were carried out for the historical Ulu Mosque’s minaret in Bitlis (Turkey), located in the Van Lake basin, using both on-site measurements and finite element methods. Detailed historical and architectural features were given for the minaret and the mosque. In addition to four different earthquake ground motion levels of 2%, 10%, 50% and 68%, structural analyses were deployed separately for seven different geographical locations in the same seismic risk area. Moreover, time history analyses were conducted using the acceleration records of the Van earthquake that occurred in the region. The minaret performance levels were determined by using the displacement values obtained. The study examined the different probabilities of exceedance and the changes in the regions with the same seismic risk. As a result of each structural analysis, base shear forces, displacement, period and maximum stress values were obtained for the minaret. The displacement, base shear force, and stress values increased as the exceedance probability decreased. While the same seismic and structural analysis results were obtained for the selected settlements in the same earthquake zone in this study, remarkable differences were observed for these settlements using the geographical-location-specific design spectrum.

AbstractA seismic change in the residential pattern is emerging in rural China today: traditional rural houses have been rapidly erased from the face of the countryside with large numbers of peasants being relocated to modern high-rise buildings. This process of “peasant elevation” has had a monumental impact on rural China. It redefines the entitlement to land use by the rural citizenry and negotiations for a new regime of property rights concerning land administration, while, most importantly, it undermines the position of the local state in rural China, whose authority is an aggregation of three distinctive elements: coercive power inherent in the state apparatus, control over economic resources, and resonance with local morality. Based on original data collected in Chongqing, Nantong and Dezhou, this paper argues that the comprehensive uprooting of the Chinese peasantry from the land and the resulting complications have caused moral disorientation among the relocated peasants and fragmentation of local authority. The difficulty in establishing community identity in the new setting has further undermined local governance. This may in turn trigger a wave of social and political tensions that may eventually turn out to be a major political challenge to the regime for years to come.

Surface faulting is, together with strong ground shaking, a hazard associated with major earthquake faults. Assessing surface faulting potential of a given active tectonic structure is a fundamental prerequisite to adequately plan the use of territories and to perform new constructions, in order to act practices aimed to mitigate the associated risk. Assessing the surface faulting potential represents also ground for correctly performing re-construction and retrofitting of buildings and infrastructures during post-earthquake activities. We investigated a branch of a major seismogenic normal fault in the central Apennines of Italy, the Campi-Preci fault, along which the monumental Sant’Eutizio Abbey is located. The medieval Abbey is one of the most important cultural/religious edifices of the central Apennines, heavily damaged by the MW 6.5 October 30, 2016, earthquake, focused a few km to the south. Our study, based on field geological, geomorphological and structural survey and trenching investigations revealed that I) the trace of the Campi-Preci active fault branch is not actually located where presently reported in the available literature, II) the supposed morpho-tectonic features (basically, some km-long scarp carved on the Meso-Cenozoic carbonate bedrock), that suggested the presence of the fault segment in the area of the Sant’Eutizio Abbey, are not related to the active fault but are probably associated to a presently inactive reverse fault and III) the Sant’Eutizio Abbey is likely not potentially affected by primary surface faulting. Our work highlights that only a comprehensive multidisciplinary approach allows to correctly assess surface faulting potential in both seismotectonic and engineering perspectives.

Abstract. The monumental heritage of European historic centres is characterised by special building types that have drawn, more than others, on the vernacular language of the local traditional architecture. The traditional bell towers, even if built by a specific (but not always known) designer, often have some building elements transliterated from the construction tradition of poor and rural buildings. This language can be found in many examples from different historical periods and in faraway areas, such as Italy and Spain. The external monumentality may not correspond to a complex spatial articulation inside the towers. Instead, it is usual to find belfries in which the vertical connections and any horizontal structures are solved by wooden stairs and floors to reach the bell cell. The used materials and building techniques reveal the design simplicity but also the evidence of a lost “know-how”. Due to the nature of the materials, possible damages and lack of maintenance, many of these structures have undergone restoration or transformation works, also whit their replacement for the benefit of most modern construction systems. The research aims to underline the central importance of preventive knowledge of these traditional structures and illustrate some significant cases in Eastern Sicily, a high seismic risk area. These case studies are emblematic for the evidence of several original structures or the extreme effects of the 20th-century interventions. These last works have often compromised the historical and documentary trait of the wooden structures, introducing new vulnerabilities due to the excessive stiffening of the masonry.

Surveying a monumental building damaged by the earthquake means to analyse its geometries, the structural elements, the connection still exist between the different parts, in order to define its state of conservation, to make structural analysis and to plan a proper project of restoration, consolidation, seismic improvement or addition of new elements. The survey of structural geometry represents the first necessary moment of building’ knowledge investigation, to be performed after the securing of the building by the Firefighters or Civil Protection. How and by which instruments the geometric analysis are conducted depends on many factors, not always exclusively on the will of the experts involved in the restoration project, but more often dictated by political, technical, social or economic needs. The accurate geometrical survey is referred as fundamental operation even by national <i>Directive for evaluation and earthquake risk reduction of cultural heritage</i> (GU n. 24 &amp;ndash; 29/01/2008 and 2011 updates), which defines guidelines for preventive interventions on built heritage in order to make the structures less vulnerable in case of earthquake. <br><br> Nowadays, the wide use of tools and accurate surveying techniques makes it possible to achieve an adequate level of accuracy of information related to the buildings, overcoming the difficulties due to accessibility of the damaged structures. <br><br> The geometrical survey of the Basilica of Santa Maria di Collemaggio in L'Aquila, was made by Politecnico di Milano starting from 2013, within the project "Ripartire da Collemaggio" (<a href=" http://www.ungiornoacollemaggio.it/content/2027"target="_blank">http://www.ungiornoacollemaggio.it/content/2027</a>), financed by Eniservizi. The basilica, an important symbol for the community of L'Aquila, was gravely damaged by the earthquake of 6^th April 2009. The objective of Eni was to turn the restoration of the building in a re-birth moment for all the community. The knowledge step was aimed to plan a restoration project able of returning the basilica to a safe and full use. In the two years knowledge investigation steps (geometric survey, historical and stratigraphic analysis, materials investigation, structures and soils examination, <i>in situ</i> tests and numerical elaborations) was involved an interdisciplinary group of researchers from various Italian universities, Politecnico di Milano, Università La Sapienza in Rome and the University of L'Aquila, called to provide a scientific advice to the Soprintendenza ai Beni Architettonici e Paesaggistici per l’Abruzzo, project manager of the restoration step. In early 2016 the yard of restoration was opened and it is still on-going. <br><br> The geometrical survey of the basilica was aim to investigate, measure and represent the exact geometry of the damaged structures and their three-dimensional complexity; the survey was planned choosing the tools and methods most appropriate in relation with the accessibility and safety of the structures, the operating ranges of acquisition and the level of detail required by the analysis and the project. This meant to integrate global and local surveying techniques, in order to cross relate data derived by different tools and to make the graphical restitution of the entire monumental complex: topography, laser scanning, photogrammetry, but also hands on instruments, at a scale of representation from 1&amp;thinsp;:&amp;thinsp;1 to 1&amp;thinsp;:&amp;thinsp;50. The laser scanner survey, registered in the accurate geomatics network, responded to the need to punctually investigate and interpret the geometrical configuration of different spaces of the Basilica, as well as its structural articulation, enabling a series of horizontal and vertical profiles, as requested by various experts involved in the diagnostic steps. <br><br> HBIM model (Historical Building Information Modeling) of the entire basilica was primarily intended as a tool for stereotomic description of the building and its parts, following the constructive logic of each structural element; then it was used as a support tool for the restoration simulation, project, management and yard. To perform the division of the building in its constructive elements, sometimes it has been used stratigraphic methodologies and instruments of analysis. The entirety of the geometric and structural complexity of the basilica, was guarantee using sophisticated 3D software and drawing complex entities, integrated and stored in the parametric BIM logic. This process has allowed to accurately and timely represent the geometry of the structural elements, of the areas characterized by crushing, empties, variations of the masonry sections and out of plumbs. <br><br> It is on the pillars of the nave that was focused the attention of survey: the will to preserve as much as possible the existing structures, in their material authenticity, required a careful analysis of each individual stone element of each pillar, investigated in its geometry, texture and state of conservation. The aim of the project was to ward a complete replacement of the pillars, preferring instead a removing and replacing intervention of only of the stone ashlars completely deteriorated and no longer recoverable, considering the question of structural safety as fundamental. The HBIM of the basilica had the primary function of connecting into one virtual space all the available data; that model has also been made as a tool for managing the restoration yard, supporting the computation of stone to buy, quarry and grossly slot, saving time on site. <br><br> Different and complementary skills were used in every knowledge and restoration steps; the accurate analysis of the structures made it possible to plan a consolidation and restoration project as close as possible to the structural conception of the existing building, adding only the new structural elements necessary to increase the resistance and to guarantee the safety of the structures, also in case of new earthquake. The Italian <i>Codice dei Beni culturali e del paesaggio</i> (DL n.42/2004), at paragraph 4 of art. 29, states that the restoration includes structural improvements. For the restoration of Collemaggio the solutions chosen were the ones able to be more effective and, at the same time, less invasive, more respectful as possible of the sacredness of the architecture, its highest historical significance, the authenticity of the material and its cultural significance. <br><br> The main principles and criteria of restoration were: maximum correspondence of conservation doctrine, with a focus on improving the structural characteristics compared to the seismic risk; exemplarity of the management practices of the restoration process; exemplarity of innovative techniques; transparency of all processes and accurate communication of cultural and scientific content. Despite of some inevitable compromises, the detailed knowledge of the building allowed to design punctual interventions, inserting new structures where the oldest were collapsed and consolidating damaged elements, in order to improve the global safety of the building but without modifying substantially the structural conception of the stratified basilica.

AbstractThe present paper deals with the elaboration of a methodology to assess the macro-seismic risk of monumental historical buildings, representing a fundamental part of the European cultural assets. Monumental buildings typically arise from a very complex constructive and morphological evolution process characterised by modifications occurred over the centuries. Therefore, they are usually heterogeneous buildings similar to 'structural aggregates' rather than single constructions and characterised by a structural behaviour depending on the mutual interaction of different structural units. An accurate knowledge process can allow the determination of structural units within the complex: such units can be therefore analysed using a specific evaluation form conceived to provide a 'risk ranking' of the different portions constituting the aggregate and accounting for vulnerability, exposure and seismic hazard parameters. The proposed methodology exploits what is already used to quickly determine structural features and eventual damages in the post-earthquake phase for ordinary buildings, introducing specific aspects typical of historical-cultural heritage requiring attention. According to the results achieved, retrofit interventions or deepen investigations can be planned for units provided by a higher position in the risk scale, optimising and rationally planning the use of available economic and time resources. In the present work, the proposed methodology is applied to the monumental complex of the Certosa di Calci, Pisa (Italy).

L’attività di ricerca si è sviluppata con l’obiettivo di sperimentare i metodi e le tecniche di acquisizione, gestione e rappresentazione tridimensionale mediante l’uso del laser scanner per offrire un valido supporto alla documentazione e alla diagnostica finalizzate alla conservazione del nostro patrimonio culturale costruito. L’ampia diffusione delle tecniche di scansione non ci consente ancora di considerare concluso un tema di ricerca che erroneamente oggi si identifica soprattutto con la fase di “acquisizione dei dati”. Il problema è in realtà posposto alle fasi successive di elaborazione e rappresentazione e sono molti i quesiti a cui si cerca di rispondere in un tentativo di integrazione culturale tra restauro, geomatica ed elettronica: è insieme una sfida e una opportunità dove si tenta di superare le barriere linguistiche, dovute a differenti ambiti culturali, diversi approcci metodologici e vari percorsi formativi. Lo studio è condotto a livello multi-scala: a scala dell’edificio, con la Basilica di Santa Maria dell’Umiltà di Pistoia, nell’ambito della convenzione di ricerca stipulata tra il Laboratorio di Geomatica per i Beni Culturali dell’Università degli Studi di Firenze e la Soprintendenza per il Patrimonio Storico Artistico ed Etnoantropologico per le province di Firenze, Pistoia e Prato, in vista del restauro e del consolidamento dell’importante struttura rinascimentale; a scala urbana, con le Torri di San Gimignano, in occasione del progetto “RIschio Sismico negli Edifici Monumentali (RISEM)” finanziato dalla Regione Toscana e coordinato dal Dipartimento di Ingegneria Civile e Ambientale dell’Università degli Studi di Firenze, per la definizione del rischio sismico. I casi studio analizzati hanno portato alla consapevolezza che, a partire dalla banca dati tridimensionale, sempre aggiornabile e interrogabile, è possibile modulare l’elaborazione in funzione degli obiettivi interdisciplinari condivisi. Si propone, pertanto, un utilizzo nuovo della tecnica di rilievo laser scanning: l’attenzione non si pone specificatamente sugli elementi artistici e architettonici e lo scopo non è solo restituire in modalità tridimensionale un oggetto al fine di effettuare valutazioni qualitative di natura storica e culturale. L’idea è approcciarsi al dato laser con occhio critico nei confronti della struttura stessa e delle geometrie più o meno complesse. L’attenzione si sposta sugli elementi costitutivi e costruttivi, su eventuali testimonianze di fessurazioni e deformazioni critiche per l’effettiva stabilità della struttura. La necessità di disporre di un “modello irrefutabile”, a cui riferire le scelte progettuali, costituisce l’ossatura portante della ricerca. Goal of the research has been to test laser scanning acquisition, management and threedimensional representation methods and techniques to provide a valid documentation and diagnostics support aimed at the preservation of our cultural built heritage. The widespread use of scanning techniques does not allow to consider concluded yet a research topic that today is mistakenly identified especially with the phase of data acquisition. Actually the problem is postponed to the later stages of processing and representation and there are many issues partially solved through an attempt of cultural integration between restoration, geomatics and electronics: it is both a challenge and an opportunity, which carries along an effort to overcome language barriers, due to different cultural backgrounds, methodological approaches and educational paths. The study has been conducted with a multi-scale approach: at the building scale, with focus on the Basilica of Santa Maria dell’Umiltà in Pistoia, within the research agreement signed by the Laboratory of Geomatics for Cultural Heritage of the University of Florence and the Soprintendenza per il Patrimonio Storico Artistico ed Etnoantropologico per le province di Firenze, Pistoia e Prato, in view of the restoration and reinforcement of the relevant Renaissance architecture; at the urban scale, within the project “Seismic Risk in Monumental Buildings (RISEM)” funded by the Region of Tuscany and coordinated by the Department of Civil and Environmental Engineering of the University of Florence, for the seismic risk evaluation related to the San Gimignano towers. The above-mentioned case-studies raised the awareness that, on the basis of the 3D data set, which can be updated and queried at any time, it’s always possible to adjust the processing phase according to the fixed interdisciplinary goals. It is therefore proposed a new use of the laser scanning surveying technique: attention is not specifically given to the artistic and architectural elements and the aim is not only to represent an object in three-dimensions in order to make qualitative assessments on its historical and cultural value. The idea is to read data from laser scanning with the intent to review critically the structure and the more or less complex geometries. Focus is shifted on the constituent and constructive elements, on any evidence of cracks and deformations which may weaken the stability of the structure. The need for an “irrefutable model”, which can be used to orient any restoration plan, globally frames the research.