Search

Masonry building aggregates can be found throughout historical city centers of Europe. Adjacent buildings have often developed during the long densification process, without consistent planning or engineering. It is common for neighboring units to share a structural wall with the connection between the units ensured through interlocking stones or a dry joint. Another consequence of the gradual development through the years are the different material properties, distributions of openings, and different roof and floor heights of the neighboring units. The difference in properties and the uncertainty related to the connection between the units leads to difficulties when modelling the seismic response. For that reason, units of an aggregate are often modelled as separate or perfectly connected. Both simplifications can lead to an incorrect estimation of the aggregate response. One of the principal reasons impeding the advancements in this area is the lack of large-scale experimental campaigns, due to the size and the cost of such campaigns. For that reason, the project AIMS (Seismic Testing of Adjacent Interacting Masonry Structures), included in the H2020 project SERA has the objective to provide the experimental data on the behaviour of an aggregate of two stone masonry buildings under bi-directional horizontal acceleration. The test unit is constructed at half scale, with one storey building and a two-storey building. The buildings share one common wall and the façade walls are connected by dry joints. Units have different floor heights and floor beam orientations, leading to a complex dynamic response. The shake table test is conducted at the LNEC seismic testing facility. Extensive instrumentation, including an optical displacement measurement system, displacement transducers, and accelerometers are used to provide information on the force-displacement response. Special attention is devoted to the interface opening and the global behaviour in relation to the interface separation.

In 1356, Basel was subjected to an earthquake with an estimated magnitude of 6.6; it is the largest known historical earthquake in central northern Europe. During this earthquake and the fire that followed large parts of Basel were destroyed. Such an event can occur again at any time in the future. To be prepared, it is essential to evaluate the seismic resistance of the existing building stock. The character of the city centre of Basel results largely from its naturally grown fabric of stone masonry buildings from different epochs. Stone masonry buildings belong to the most vulnerable structures under seismic excitation. At the same time, they are part of the Swiss cultural heritage and not only their appearance but also the structure as such should be maintained. This paper reports on a collaborative project between EPFL and the University of Pavia, which aims on the one hand at developing realistic models for the seismic response of stone masonry buildings and on the other hand at developing minimum intervention strategies that are reversible and as little intrusive as possible and therefore suitable for cultural heritage buildings. This paper describes first findings from the various experimental campaigns that are part of the project and explores how stone masonry typologies can be analysed using image analysis procedures.

In many historical centers in Europe, stone masonry is part of building aggregates, which developed when the layout of the city or village was densified. The analysis of such building aggregates is very challenging and modelling guidelines missing. Advances in the development of analysis methods have been impeded by the lack of experimental data on the seismic response of such aggregates. The SERA project AIMS (Seismic Testing of Adjacent Interacting Masonry Structures) provides such experimental data by testing an aggregate of two buildings under two horizontal components of dynamic excitation. With the aim to advance the modelling of unreinforced masonry aggregates, a blind prediction competition is organized before the experimental campaign. Each group has been provided a complete set of construction drawings, material properties, testing sequence and the list of measurements to be reported. The applied modelling approaches span from equivalent frame models to Finite Element models using shell elements and discrete element models with solid elements. This paper compares the first entries, regarding the modelling approaches, results in terms of base shear, roof displacements, interface openings, and the failure modes.

The seismic performance of unreinforced masonry buildings is commonly assessed using equivalent frame modelling. Its computational efficiency allows for a large number of analyses to be conducted, which are often required to account for epistemic and aleatoric uncertainties. To obtain a full description of the building response, in‐plane and out‐of‐plane failure modes need to be considered, though previous elements for equivalent frame models of unreinforced masonry buildings only account for the in‐plane response. This paper presents the formulation of a three‐dimensional macroelement for modelling the dynamic in‐plane and out‐of‐plane behaviour of masonry panels, which extends the approach of a previously developed macroelement to simulate the in‐plane response. The proposed three‐node, three‐dimensional macroelement is implemented in the software OpenSees and describes the main features of the in‐plane and out‐of‐plane behaviour of a masonry wall, including second‐order geometrical effects and a coupled shear/flexural response. It also allows for the use of complex material models. The proposed element is used to simulate experimental results for in‐plane shear‐compression tests and out‐of‐plane free vibration tests of masonry panels. The implemented element, as well as the example models, is openly shared through the repository https://github.com/eesd-epfl/OpenSees/wiki.

The region of Basel is considered one of the most seismically vulnerable in Switzerland: in 1356, a very damaging earthquake hit the city, which nowadays is characterized by a significant concentration of population and economic activities. Hence, the Canton of Basel and the Swiss Federal Office for the Environment have promoted a comprehensive experimental and numerical research program, spanning from the evaluation of the seismic vulnerability of Basel's heritage building stock to the identification of appropriate retrofit strategies. In particular, the experimental program aims at characterizing the mechanical properties of natural stone masonry and investigating the seismic performance of building aggregates typical of the historical city center. To this end, a unidirectional shake-table test was performed on the half-scale model of a natural stone masonry building aggregate, incorporating the main architectural and structural features of existing buildings in Basel's historical center. The aggregate consisted of two three-story units. Double-leaf rubble stone masonry walls, with undressed blocks and river pebbles, constituted the vertical structural elements, while timber floors, simply supported by the transverse walls, provided flexible horizontal diaphragms. The two units were covered by roofs with different truss configurations, pitches, and side-gable wall heights. An incremental, unidirectional dynamic shake-table test was performed up to near-collapse conditions of the specimen, using input ground motions representative of realistic seismic scenarios (natural and induced) for the examined region. The selected records were scaled at different amplitudes, reaching spectral accelerations close to twice those associated with a 475-years return period for the region. The experimental response of the prototype building was also simulated via nonlinear static analysis. The structure was modeled using an equivalent-frame approach with nonlinear macroelements, as implemented in the TREMURI software. The numerical results were compared with the experimental response in terms of pushover and backbone curves and lateral displacement envelopes. The consistency between numerical simulations and experimental results was also verified in terms of damage pattern and activation of damage mechanisms.

Im Jahr 1356 wurde Basel von einem Erdbeben mit einer geschätzten Momenten-Magnitude von 6.6 erschüttert. Während dieses Erdbebens und des nachfolgenden Feuers wurden grosse Teile von Basel zerstört. Ein solches Ereignis kann jederzeit wieder auftreten. Um vorbereitet zu sein, ist es wichtig, das erwartete Erdbebenverhalten der bestehenden Gebäude zu ermitteln. Der Charakter des Stadtzentrums von Basel ist stark von historischen Natursteinmauerwerksgebäuden aus verschiedenen Epochen geprägt. Natursteinmauerwerksgebäuden gehören zu den am stärksten gefährdeten Strukturen unter Erdbebenanregung. Gleichzeitig gehören sie zum Schweizer Kulturerbe und das nicht nur hinsichtlich ihres Aussehens sondern auch hinsichtlich der Bausubstanz als solche. In diesem Beitrag wird ein Forschungs- und Weiterbildungsprojekt, das gemeinsam von EPFL und der Universität Pavia ausgeführt wird, vorgestellt. Das Projekt hat zum einen zum Ziel realistischer Modelle für das Erdbebenverhalten von Natursteinmauerwerksgebäuden zu entwickeln und damit die Gebäude zu identifizieren, die keine Intervention benötigen. Zum anderen sollen Verstärkungsmassnahmen entwickelt werden, die reversibel und so wenig invasive wie möglich sind und daher auch für Kulturgüter geeignet sind. Die Forschungsresultate werden in parallel laufenden Weiterbildungskursen direkt in die Ingenieurpraxis vermittelt. In diesem Beitrag wird das Forschungsprojekt vorgestellt und es werden erste Ergebnisse beschrieben., Tagungsband der 15. D-A-CH Tagung in Weimar: Erdbebeningenieurwesen und Baudynamik, ISBN:978-3-930108-13-5

Recent zijn er een reeks levensgrote schudtafeltesten uitgevoerd op drie identieke ongewapende metselwerkgebouwen door de Universiteit van Pavia en het Europees Centrum voor Training en Onderzoek in Aardbevingstechniek. De testen onderzochten het dynamisch gedrag van de gebouwen onder één-, twee- en driedimensionale seismische bewegingen. Het numeriek simuleren van de seismische respons van niet-structurele ongewapende metselwerkcomponenten onder tweedimensionale (zijnde horizontale en verticale) inputacceleraties blijkt gevoelig te zijn aan meerdere parameters. De bestaande literatuur op de invloed van deze inputparameters op het dynamisch gedrag was tot recent beperkt. Deze masterproef simuleert het experimentele seismische gedrag van schoorstenen, borstweringen en gevelmuren onder meerdimensionale acceleraties en evalueert het ontstane scala aan waarden voor de inputparameters. De simulaties zijn uitgevoerd met Trilly, een programma voor de analyse van het dynamische gedrag van ongewapende lokale metselwerkmechanismen via vereenvoudigde systemen met één vrijheidsgraad. Het vergelijken van de numerieke en experimentele respons van de componenten toont aan dat de software op een accurate manier het dynamisch gedrag voor zowel één- als meerdimensionale acceleraties kan simuleren. De resultaten tonen hierbij de inputparameterwaarden. Bovendien is er een vergelijking uitgevoerd naar de efficiëntie van de verschillende dempingsmodellen. Hieruit blijkt de constant damping coefficient het meest betrouwbaar te zijn.

In a country with high seismic risk, such as Italy, the activities to raise awareness about the seismic risk are of primary importance. The Inarcassa Foundation, the National Council of Engineers and the National Council of Architects with the scientific support of the Superior Council of Public Works, the Italian Civil Protection Department, the Conference of Italian University Rectors and the Laboratories University Network of Earthquake Engineering have launched the national awareness campaign, named "Diamoci una scossa!". As part of this campaign, technical and informational visits to residential buildings were carried out by architects or engineers expert in seismic risk. A special form, called “Diamoci una scossa!” form, was compiled by the technicians during technical-information visits. This form was prepared starting from similar forms already used in Italy, such as the AeDES form, the Cartis Building form and the CLE US1 form. On the basis of the acquired data related to the current seismic risk, the construction age and the vulnerabilities of buildings, it was possible to associate a color to the building (green / yellow / red). This color provides generic indications on the possible risk class of the building according to the classification provided by the Sisma Bonus fiscal benefits and on the urgency for a in-depth building assessment according to seismic code. The present work, after a brief description of the awareness campaign and related activities, deal with the "Diamoci una scossa!" form and the criteria adopted for assigning the color based on the data collected regarding each specific building.

La valutazione del rischio sismico a scala territoriale è fondamentale per la gestione dell’emergenza post-terremoto, quantificazione delle perdite socio-economiche dovute a terremoti futuri, definizione di strategie di mitigazione del rischio, ottimizzazione di piani di intervento. Affinché le conseguenze dovute a futuri eventi sismici possano essere efficacemente mitigate, è necessario disporre di stime di rischio accurate e affidabili. In questo contesto, la difficoltà principale è legata alla definizione del rischio stesso, che, risultando dalla convoluzione di pericolosità, esposizione e vulnerabilità, richiede il coinvolgimento di diverse discipline scientifiche. In questo lavoro, modelli di vulnerabilità per edifici residenziali in muratura e c.a., derivati empiricamente sulla base di dati di danno post-terremoto, sono implementati nella piattaforma nazionale del rischio sismico, al fine di produrre stime di rischio a scala territoriale. Diversi sono i casi studio presentati, focalizzati sulla valutazione del rischio incondizionato. I risultati sono mostrati per diversi tipi di conseguenze, quali vittime, perdite economiche, impatto in termini di abitazioni inagibili e crollate e numero di sfollati.

Questo lavoro presenta curve di fragilità empiriche per il costruito esistente in c.a., da utilizzare per la valutazione del rischio sismico a scala territoriale. Le curve sono state derivate elaborando statisticamente i dati di danno postterremoto raccolti nella piattaforma Da.D.O., utilizzando l’accelerazione di picco al suolo (PGA) stimata da shakemap come misura di intensità per la caratterizzazione dello scuotimento. Gli edifici in c.a. sono classificati in quindici tipologie edilizie, identificate sulla base del numero di piani (da 1 a 5 piani) e tipo di progettazione (edifici progettati per soli carichi gravitazionali, per carichi sismici pre-1981 e post-1981). In primo luogo, le curve di fragilità sono state derivate per le tipologie edilizie identificate e per cinque livelli di danno della EMS-98, tenendo conto del danno osservato su componenti strutturali e non strutturali. Successivamente, si sono derivate curve di fragilità per due classi di vulnerabilità a vulnerabilità decrescente e tre classi di piano, pesando le curve di fragilità tipologiche sulla base della composizione del costruito esistente.

Scopo del “Sendai Framework for Disaster Risk Reduction 2015-2030” è fornire le linee guida per la gestione delle catastrofi multi-rischio al fine di ridurre sostanzialmente le perdite di vite umane, dei mezzi di sussistenza, nonché economiche, dei beni sociali, culturali e ambientali legati a persone, imprese, comunità e paesi. Con questo obiettivo, nel 2018 il Dipartimento della Protezione Civile italiano (DPC) ha prodotto un documento che illustra la valutazione dei rischi per l’intero territorio nazionale, e le relative elaborazioni, condotte con il sostanziale contributo della comunità scientifica. Per il rischio sismico, è stata sviluppata l’analisi del rischio del patrimonio edilizio residenziale con il coinvolgimento della comunità scientifica italiana attiva nel settore. Assumendo il modello della pericolosità sismica del territorio nazionale prodotto da INGV nel 2004, EUCENTRE (Centro europeo per la formazione e la ricerca nell’ingegneria sismica) e ReLUIS (Rete dei Laboratori Universitari di Ingegneria Sismica) hanno lavorato e collaborato per mettere a punto diversi modelli di vulnerabilità/esposizione validi per gli edifici residenziali e valutare il relativo rischio sismico. Per effettuare le elaborazioni e poter confrontare facilmente i risultati ottenuti con i diversi approcci scientifici adottati dalle unità di ricerca coinvolte, EUCENTRE, su incarico del DPC, ha realizzato la piattaforma IRMA (Italian Risk MAps), che permette di caricare diversi modelli di vulnerabilità/esposizione, effettuare separatamente le elaborazioni del rischio, confrontare e combinare i risultati ottenuti. La collaborazione tra EUCENTRE e ReLUIS, con il coordinamento del DPC, ha portato nel dicembre 2018 alla produzione delle mappe di rischio sismico per il territorio italiano pubblicate nel documento National Risk Assessment (NRA) di valutazione del rischio nazionale

The seismic assessment of masonry buildings, both modern unreinforced masonry (URM) buildings and historical heritage constructions, is a complex task, characterised by a several sources of uncertainty, which regard the appropriate modelling of strategy the problem, the model parameters, and the seismic input. In order to properly account for all sources of uncertainty and provide a robust risk estimate, simple models to be run under different conditions are necessary. In this regard, equivalent frame modelling of masonry buildings is a modelling approach which can produce reliable estimates of the seismic demands, in terms of displacement and accelerati, for buildings showing a predominant in-plane failure mode. The simplicity of the approach allows performing multiple simulations at a reasonable computational cost. This thesis concentrates on the extension of the equivalent frame approach for the modelling of both the in-plane and the out-of-plane response of masonry buildings. Making use of the computational simplicity of equivalent frame models, it further proposes an approach for the probabilistic assessment of buildings, which aims at being potentially applicable also outside the research domain, to which probabilistic methods are mainly confined at the state of the art. In order collect information on the uncertainties related to the assessment of the in-plane behaviour of masonry, with a particular regard to stone masonry, a database of 128 shear compression tests on walls was collected and analysed. Distributions and median values of the most relevant material properties were derived, including the displacement capacities at cracking, yielding, maximum force capacity, significant damage and collapse limit states. Moreover, the uncertainty on the determination of force capacity and stiffness was discussed. This data was then used to apply to a case study a simplified approach for the explicit introduction of uncertainty in a seismic assessment of a stone masonry building. The method was compared to established approaches of similar complexity and a reference Monte Carlo simulation. From the analysis, the relative impact of all sources of uncertainty on the total model uncertainty could be evaluated, showing the major relevance of the displacement capacity in determining the seismic performance. Secondly, a formulation of a macro-element model for the simulation of the in-plane and out-of-plane response of masonry walls is proposed. Its use in simulating from small element tests to shaking table tests on entire buildings is shown. The proposed macro-element is able to describe the out-of-plane dynamic response of buildings, showing the major sources of vulnerability and simulating the effect of the quality of connections on the global response, both in terms of displacement demands and failure modes.

Tese de Doutoramento. Engenharia Civil. Faculdade de Engenharia. Universidade do Porto. 2012

Mestrado em Engenharia Civil A frequência com que a humanidade tem sido confrontada com catástrofes naturais, em particular de foro sísmico, justifica a necessidade em aprofundar os conhecimentos dos materiais de construção e das características das estruturas em que o Homem habita, especialmente o conjunto das construções tradicionais e históricas em alvenaria, estruturas predominantes nos centros históricos das cidades. O desempenho sísmico das estruturas em alvenaria é especialmente difícil de caracterizar uma vez que depende diretamente de uma multiplicidade de detalhes estruturais. Não obstante, o presente trabalho procura contribuir para o maior conhecimento da atuação da construção em alvenaria face à resposta sísmica. Para esse fim, a primeira parte do estudo é dedicada à comparação entre a regulamentação de construções em alvenaria, americana e europeia. Deste modo pretende-se contribuir-se para o desenvolvimento de uma regulamentação cada vez mais consistente, capaz de mitigar a vulnerabilidade sísmica desta tipologia construtiva. Num segundo momento da investigação, com o intuito de estudar o comportamento sísmico de edifícios antigos com paredes em alvenaria de pedra tradicional, realizou-se uma análise numérica com recurso ao programa Ansys, tomando como base a campanha experimental realizada com estruturas à escala real desenvolvida no EUCENTRE, em Pavia, Itália. A utilização do programa Ansys permitiu simular parte da campanha experimental, pelo que foi possível aumentar os conhecimentos no campo da vulnerabilidade sísmica deste tipo de construções. A análise numérica assentou na construção de dois modelos numéricos para simular um abalo sísmico de acordo com os ensaios experimentais. O primeiro modelo simulou uma estrutura com um pavimento de diafragma flexível e o segundo modelo foi reforçado com 8 tirantes, que serviram como reforço estrutural no ensaio experimental. É especialmente relevante sublinhar os últimos resultados da simulação não linear dinâmica do primeiro modelo, uma vez que traduzem claramente a tendência do mecanismo de colapso potencial que se veio a verificar no ensaio experimental da construção em alvenaria não reforçada. Antecedendo esta análise, recorreu-se ainda ao programa Seismosignal para determinar os deslocamentos medidos pelos acelerómetros instalados na estrutura dos testes experimentais. Deste modo, os resultados dos deslocamentos permitiram consolidar a interpretação dos resultados da análise numérica. The frequency with which the humanity has been confronted with natural disasters, namely earthquakes, justifies the need to enhance knowledge on construction materials and the characteristics of the structures in which humans live, especially the traditional and historic masonry building stock, structures predominant in historical city centers. The seismic performance of masonry structures is particularly difficult to characterize since it is directly dependent on a multiplicity of structural details. Nevertheless, this work aims to contribute to a better knowledge of the performance of masonry construction concerning the seismic response. To achieve this goal, the first part of this study focused on a comparison between the masonry construction codes, American and European. By that it is intended to contribute to the development of a more consistent regulation, capable to mitigate the seismic vulnerability of this construction typology. In a second moment of this research, in order to study the seismic behavior of the old buildings with traditional stone masonry walls, it was carried out an numerical analysis using the Ansys program, based on the real-sized experimental campaign developed in EUCENTRE, in Pavia, Italy. The use of the Ansys program allowed the simulation of part of the experimental campaign, therefore it has able to increase the knowledge in the field of seismic vulnerability of such buildings. The numerical analysis was based on the construction of two numerical models to simulate an earthquake according to the experimental trials. The first model simulated a structure with flexible floor diaphragm and the second model was retrofitted by adding eight tie-rods, which worked as structural reinforcement in the experimental testing. It is especially important to underline the latest results of the non-linear dynamic simulation on the first model, as they clearly reflected the trend of the potential collapse mechanism that was verified on the experimental test of the non-reinforced masonry construction. Previous to this analysis, we used the Seismosignal program to determine the displacements measured by the accelerometers installed in the structure of the experimental tests. In this way, the results of the displacements allowed us to consolidate the interpretation of the results from the numerical analysis.