Reduction of the seismic vulnerability of vernacular architecture with traditional strengthening solutions

Tese de Doutoramento em Engenharia CivilThe valorization and preservation of vernacular architecture, as well as traditional construction techniques and materials, is a key-element for cultural identity. As part of this essential objective, the present thesis focuses on vernacular architecture earthquake preparedness, with a particular focus on the Portuguese case. Conservation efforts are often mainly focused on historical constructions and monuments. Furthermore, more detailed and sophisticated seismic vulnerability assessment approaches typically used for monumental buildings require time, cost and resources that are not commonly assigned to the study of vernacular architecture. Earthquakes come unexpectedly, endangering in-use vernacular architecture and the population who inhabits it. That is why the development of a simplified method for the seismic vulnerability assessment of vernacular architecture is of paramount importance. The present research establishes four clear objectives that are accomplished through the development of four research tasks structured along the nine chapters that composed this document. The first part of the thesis is dedicated to the investigation of traditional strengthening construction techniques developed empirically by local communities to protect their built-up environment, based on literature review and on-site visits. The second part deals with the development of two seismic vulnerability assessment methods for vernacular architecture: (1) Seismic Vulnerability Index for Vernacular Architecture (SVIVA); and (2) Seismic Assessment of the Vulnerability of Vernacular Architecture Structures (SAVVAS). The development of these two methods composes the main body of the thesis, which is carried out on the basis of an extensive numerical modeling campaign that also helped to gain a deeper quantitative knowledge on the seismic behavior of representative examples of existing Portuguese vernacular architecture. The third part of the thesis addresses the numerical investigation of traditional strengthening construction solutions identified within the first part. It is mainly intended to validate their efficiency in mitigating the seismic vulnerability of vernacular architecture for their eventual application. Finally, the thesis deals with the application of the two methods in two different case studies. This part allows calibrating the two methods, as well as validating their applicability as first level seismic vulnerability assessment approaches.A valorização e conservação da arquitetura vernácula, assim como das técnicas e materiais tradicionais de construção, é um elemento chave de identidade cultural. A presente tese centra-se na arquitetura vernácula e na sua preparação para fazer face aos terramotos, em particular no caso português. Os esforços de conservação centram-se em geral nas construções históricas. Abordagens muito detalhadas e sofisticadas para a avaliação da vulnerabilidade sísmica são, sobretudo, aplicáveis em edificios históricos e monumentais, porque requerem um tempo, um custo e uma quantidade de recursos que não podem ser atribuídos ao estudo da arquitetura vernácula. Contudo, os sismos são inesperados e põem em risco a arquitetura vernácula e os seus habitantes. É por isso que o desenvolvimento de um metodo simplificado para a avaliação da vulnerabilidade sísmica da arquitetura vernácula é de suma importância. A presente investigação estabelece quatro objetivos que são atingidos através do desenvolvimento de quatro tarefas organizadas em nove capítulos que compõem este documento. A primeira parte da tese centra-se no estudo de técnicas tradicionais de reforço desenvolvidas por comunidades locais empiricamente, com o objetivo de proteger os seus edifícios das ações sísmicas. Esta parte inclui a revisão da literatura e a investigação in-situ. A segunda parte dedica-se a desenvolver dois métodos para a avaliação da vulnerabilidade sísmica da arquitectura vernácula: (1) Seismic Vulnerability Index for Vernacular Architecture (SVIVA); e (2) Seismic Assessment of the Vulnerability of Vernacular Architecture Structures (SAVVAS). O desenvolvimento destes métodos compõe o corpo principal da tese, baseado num extenso trabalho de modelação numérica, que também contribui para se obter um melhor conhecimento do comportamento sísmico de exemplos existentes e representativos da arquitetura vernácula portuguesa. A terceira parte aborda a investigação numérica das soluções de reforço tradicionais identificadas previamente e destina-se principalmente à validação da sua eficiência na mitigação da vulnerabilidade sísmica da arquitectura vernácula, para assim poder ser aplicadas em edifícios existentes. A tese é concluída com a aplicação dos dois métodos desenvolvidos, em dois casos de estudo. Esta parte contribui para a calibração dos métodos, além da validação da sua aplicabilidade como abordagem de primeiro nível na avaliação da vulnerabilidade sísmica

Safety analysis of modern heritage masonry buildings: Box-buildings in Recife, Brazil

Dissertação de mestrado em Structural Analysis of Monuments and Historical ConstructionsThere was a large increase in the construction of public housing in Brazil during the 1970s because of housing shortage and economic policies supporting development projects and private investments. Box-buildings arose in that time, constructed by non-experts interested only in a fast return on the investment. These buildings were made in an empirical way, with no consideration of specific technical norms or standards and thus, critically reducing their safety coefficient. Now, it is estimated that there are between 4,000 to 6,000 buildings constructed with these characteristics in the Recife Metropolitan Region. They are inhabited by more than 250,000 people, comprising approximately 10% of the population of this region. Around 90% of these buildings seem to present some risk of collapse, with different severity. 230 buildings are at high risk of collapse and have been evacuated. More than 100 buildings have been condemned, 5 have been demolished and 12 have already collapsed. The present dissertation focuses on a recent PhD thesis co-supervised at University of Minho carried out by de Carvalho (2010) and aims to extend it. That work is an experimental and numerical research applied to one building that suffered collapse. An extensive testing programme was carried out, including non-destructive and minor destructive testing on the building, as well as laboratory testing. A finite element model was made, updated with the data obtained through the dynamic identification, and a linear elastic numerical analysis was performed. The objective of the present dissertation is to extend the work carried out before to the non-linear regime, by incorporating the inelastic phenomena, aiming at quantifying the safety of the existing buildings and better understanding the damage and the reasons for the collapse. The research mainly comprises a safety analysis of the structure and a sensitivity analysis, in order to understand the importance of the material parameters and their influence on the structural response of the building.construção de habitação social no Brasil teve um grande impulso a partir da década de setenta devido à escassez de habitação, incentivada pelas políticas económicas que facilitaram os projetos de desenvolvimento do país na época e o investimento privado. Os prédios tipo caixão emergiram naquela época, construídos por profissionais sem experiência em construção, interessados apenas no rápido retorno desse tipo de investimento. A maior parte destas edificações foram executadas de forma empírica, sem consideração dos requisitos de regulamentação técnica específicas que possibilitassem o estabelecimento de um nivel de segurança estrutural aceitável. Atualmente, estimase que existam entre 4,000 a 6,000 edifícios com essas características construídos na Região Metropolitana do Recife (RMR) e que estes sejam habitados por cerca de 250,000 pessoas, compreendendo aproximadamente 10% da população do grande Recife. Cerca de 90% destes edifícios apresentam risco de colapso, sendo que 230 são considerados de alto risco e já foram evacuados. Mais de 100 prédios foram interditados, 5 foram demolidos e 12 sofreram colapso. O presente trabalho centra-se numa recente tese de doutoramento coorientada na Universidade do Minho realizada por de Carvalho (2010) e pretende continuar o seu trabalho. Aquela tese é uma investigação experimental e numérica aplicada a um edifício que colapsou. Foram realizados no edifício ensaios não destrutivos e semi-destrutivos, tendo ainda sido executados ensaios em laboratório de amostras retiradas das paredes do edifício. Por outro lado, realizou-se um modelo de elementos finitos, atualizado com as informações obtidas por meio de um ensaio de identificação dinâmica realizado no edifício, e completou-se uma análise elástica linear. O objetivo do presente trabalho é alargar o trabalho feito na tese para uma análise em regime não linear, incorporando a resposta inelástica para quantificar a segurança desses edifícios, entender melhor os danos e tentar identificar as causas do colapso. A investigação compreende principalmente uma análise da segurança da estrutura e uma análise de sensibilidade, a fim de entender a importância das características dos materiais e a sua influência sobre a resposta estrutural do edifício.Durante los años 70, hubo un gran aumento de la construcción de vivienda pública debido a la escasez de vivienda y las políticas económicas que apoyaban proyectos de desarrollo y la inversión privada. Los edificios tipo caixão surgieron en ese momento, construidos por profesionales sin experiencia en el campo de la construcción e interesados solamente en el rápido retorno de la inversión. Los edificios se construían de manera empírica, sin consideraciones a las normas y códigos de la época y por ello, el coeficiente de seguridad de los edificios se redujo drásticamente. Actualmente, se estima que hay entre 4,000 y 6,000 edificios construidos de esta manera en el área metropolitana de Recife (RMR). Están habitados por más de 250,000 personas, lo que comprende aproximadamente al 10% de la población total de la región. Alrededor del 90% de estos edificios presentan algún riesgo de colapso y de los cuales 230 están considerados en alto riesgo y ya han sido evacuados. Más de 100 están pendientes de demolición, 5 han sido ya demolidos y 12 han colapsado. El presente trabajo pretende continuar el trabajo empezado en la tesis doctoral realizada por de Carvalho (2010) y codirigida en la Universidade do Minho. La tesis es una investigación numérica y experimental sobre un edificio que colapsó. Se llevó a cabo un extenso programa de ensayos que incluyó ensayos no destructivos y semi-destructivos sobre el edifico, y trabajo experimental en laboratorio, con muestras extraídas del edificio. Se realizó un modelo de elementos finitos, actualizado con la información obtenida a través de un ensayo dinámico que se desarrolló sobre el edificio, y se llevó a cabo un análisis elástico lineal. El objetivo del presente trabajo es ampliar el trabajo realizado en la tesis llevando el análisis al régimen no lineal, incorporando la respuesta inelástica para así cuantificar la seguridad de este tipo de edificios y entender mejor los daños y las razones del colapso. La investigación comprende principalmente un análisis de la seguridad de la estructura y un análisis de sensibilidad, con el fin de comprender la importancia de las características de los materiales y su influencia en la respuesta estructural del edificio

Seismic-resistant building practices resulting from local seismic culture

Considering that vernacular architecture may bear important lessons on hazard mitigation, this chapter focuses on the European Mediterranean countries and studies traditional seismic-resistant architectural elements and techniques that local populations developed to prevent or repair earthquake damage. This area was selected as a case study because, as a highly seismic region, it has suffered the effect of many earthquakes along the history and, thus, regions within this area are prone to have developed a Local Seismic Culture. After reviewing seismic resistant construction concepts, a wide range of traditional construction solutions that, in many cases, have shown to improve the seismic performance of vernacular constructions of these regions is presented, as a contribution to the general overview of retrofitting building systems provided in this book. The main motivation is that most of these techniques can be successfully applied to preserve and to retrofit surviving examples without prejudice for their identity.(undefined

Modelação numérica do comportamento de tração-compressão de ligadores em paredes de alvenaria

Brick masonry veneer walls connected to infill walls inserted in a reinforced concrete (RC) frame is a very common constructive system in Portugal. The stability of the veneer wall is ensured by ties that make the connection with the masonry infill walls. These ties are the main structural element transferring the out-of-plane loads to the main structure during an earthquake. However, the characterization of the seismic behavior of these tie connections is an insufficiently explored topic. The present paper shows a numerical investigation that aims to simulate experimental results of tension and compression tests performed on masonry wallets connected by means of steel ties. The main objective of the present research is to obtain a better understanding of the complex structural behavior of this specific construction system to eventually develop simplified numerical tools to be used in engineering practice for the seismic design and retrofitting of brick masonry veneer walls.As paredes de alvenaria não estruturais de fachada constituem um dos elementos construtivos mais tradicionais das envolventes de edifícios construídos em Portugal. A estabilidade destas paredes é garantida por ligadores que fazem a ligação com as paredes de alvenaria de enchimento. Estes ligadores são o principal elemento estrutural a transferir as cargas fora do plano para a estrutura principal durante um terremoto. No entanto, a caracterização do comportamento sísmico dos ligadores é ainda um tema insuficientemente explorado na literatura. O presente artigo mostra uma investigação numérica com o objetivo de simular ensaios de tração-compressão realizados em provetes de alvenaria ligados através de ligadores metálicos. O objetivo último da investigação será obter um melhor entendimento do complexo comportamento estrutural de esta tipologia construtiva e eventualmente propor ferramentas numéricas simplificadas que possam ser usadas por engenheiros na prática profissional para o desenho sísmico e reabilitação de paredes de alvenaria de fachada.The authors acknowledge the support of the Portuguese Foundation for Science and Technology (FCT), through the financing of the research project SEVen - Development of Sustainable Ceramic Brick Masonry Veneer Walls for Building Envelops (PTDC/ECICON/30876/2017)

Seismic behavior of an old masonry building in Vila Real de Santo António, Portugal

Vila Real de Santo António is located in the Algarve region and was erected ex novo at the end of the 18th Century, after the 1755 Lisbon earthquake, following a Pombaline development that showed seismic concern at an urban and architectural level. However, most of the original constructions have been subjected to continuous alterations or even substituted for new ones. The first building built in the town was the Alfândega or Customs House and was selected as a case study because it still preserves most of its original characteristics. It was studied through historical survey, visual inspection and experimental in-situ characterization. As a result, a detailed finite element model was constructed and pushover analyses were carried out to assess its seismic vulnerability. The main goals of the paper are to understand the resisting mechanisms and seismic behavior of the building, as well as to evaluate the influence of structural alterations.NAFOSTED -National Foundation for Science and Technology(PTDC/ATPAQI/ 3934/2012

Modelling strategies for traditional earthquake resistant solutions enhancing wall-to-wall connections

Traditional masonry buildings located in seismic prone areas often present construction techniques empirically developed to improve the buildings seismic performance, for example by enhancing their box-behaviour in order to avoid premature out-of-plane failure of masonry walls. Often, earthquake-resistant techniques consist of a combination of locally available materials, such as timber or metal ties, embedded in masonry components. Finite Elements Macro-modelling approximates masonry as a homogeneous isotropic continuum, in order to obtain simpler and larger meshes, because the model does not have to describe the internal structure of masonry. One of the main challenges related to the numerical simulations is the use of adequate constitutive materials models able to replicate the non-linear behaviour of masonry. In the framework of macro-modelling approach of the masonry walls, an additional challenge is the modelling strategy to simulate the contribution of elements embedded in masonry, which work as traditional earthquake resistant solutions. This work presents the results of the numerical analyses simulating the out-of-plane response of reduced scale (1:2) U-shaped stone masonry walls built with earthquake resistant techniques embedded at the corners, namely steel ties in wall 1 and timber lath beams in wall 2, which were tested experimentally. The work primarily aims at the comparison of the results obtained with two different modelling strategies for the two reinforcing solutions, namely using 3D beams elements (CL18B) and solid elements (CHX60). The outcomes provided by this work represent a useful contribution to achieve a deeper understanding regarding the consistency of the aforementioned strategies in capturing the influence of traditional of earthquake resistant techniques on the out-of-plane response of reinforced stone masonry walls

Seismic vulnerability assessment method for vernacular architecture

The valorization and preservation of vernacular architecture, as well as traditional construction techniques and materials, is a key-element for cultural identity. As part of this essential objective, the present paper focuses on vernacular architecture earthquake preparedness. Earthquakes come unexpectedly, endangering in-use vernacular architecture and the population who inhabits it. However, conservation efforts are often mainly focused on historical construction and monuments. Furthermore, more detailed and sophisticated approaches typically used for monumental buildings require time, cost and resources that are not commonly assigned to the study of vernacular constructions. That is why the development of a simplified method for the seismic vulnerability assessment of vernacular architecture is of paramount importance. The paper firstly provides a brief overview of seismic vulnerability assessment methods, specifically the vulnerability index method, on which the proposed method is based. Then, the paper presents the procedure that was followed for the development of the seismic vulnerability assessment method for vernacular architecture proposed, which includes: (a) the identification and selection of constructive aspects and parameters that most influence the seismic behavior of the building; (b) the definition of the parameters seismic vulnerability classes by means of numerical parametric analysis using detailed finite element (FE) modeling and nonlinear static (pushover) analyses; and (c) the definition of the parameters weight, according to a statistical analysis performed on the results of the parametric study. Finally, the paper shows, as an example, the numerical strategy followed for the definition of the classes of one parameter.FEDER funds through the Competitivity and Internationalization Operational Programme–COMPETE and by national funds through FCT–Foundation for Science and Technology within the scope of the project POC1-01-0145-FEDER-007633.This work was also financed in the framework of the Portuguese Public Procurement Code,LOTE3EC5–Escola Secundária da Anadia e Gafanha da Nazar

Influência de técnicas sismo-resistentes no comportamento para fora do plano de paredes de alvenaria de pedra

FE method is a useful and powerful tool widely applied to the structural analysis of masonry constructions. One of the main challenges related to the numerical simulations is the use of adequate constitutive materials models able to replicate, in an accurate way, the non-linear behaviour of masonry. Thus, the experimental characterization of the masonry can allow overcoming the uncertainties regarding the material mechanical properties. Macro-modelling is a very popular FE approach that approximates masonry as a homogeneous isotropic continuum, in order to obtain simpler and larger meshes, because the model does not have to describe the internal structure of masonry. Hence, macro-modelling provides a good balance between accuracy and efficiency. This work presents a methodology applied to the calibration of two numerical macro-models reproducing the OOP response of reduced scale (1:2) U-shaped stone masonry walls built with earthquake resistant techniques embedded at the corners (WALL 1 – steel ties and WALL 2 – timber lath beams), which were previously tested experimentally by using an airbag to simulate the seismic load. The outcomes, provided by this work, represent a useful contribution in order to assess the effectiveness of the macro-model approach for the analysis of masonry buildings.Um dos desafios principais do uso do método de elementos finitos (FE) para a análise estrutural de construções de alvenaria é o uso de modelos constitutivos que sejam capazes de replicar apropriadamente o comportamento não linear da alvenaria. A caracterização experimental da alvenaria permite diminuir as incertezas relacionadas com as propriedades mecânicas do material. Este trabalho apresenta a metodologia aplicada para a calibração de dois modelos FE que reproduzem duas paredes de alvenaria de pedra em forma de U ensaiadas no laboratório. Os modelos seguem uma abordagem macromodelo. As paredes ensaiadas foram construídas com dois dispositivos sismorresistentes tradicionais inseridos nos cunhais, nomeadamente tirantes de aço (WALL 1) e vigas de madeira (WALL 2), e foram ensaiadas fora do plano mediante o uso de airbags para a simulação da carga sísmica. Os resultados deste trabalho contribuem para avaliar a eficácia da abordagem macromodelo para a análise estrutural de edifícios de alvenaria.The work presented in this paper was partially financed by FEDER funds through the Competitivity and Internationalization Operational Programme – COMPETE, and by national funds through FCT – Foundation for Science and Technology within the scope of the project POC1-01-0145-FEDER-007633. This work was also financed in the framework of the Portuguese Public Procurement Code, LOTE 3EC5 – Escola Secundária da Anadia e Gafanha da Nazaré

A comparative analysis of sustainable management strategies for the conservation vernacular settlements

The present paper aims to compare management strategies for the sustainable conservation of rural settlements and vernacular architecture. It addresses the difficulties that arise when analyzing this type of heritage and discusses the considerations that must be taken into account for its proper management. The process of management itself can be complex, as it requires understanding the social, cultural, environmental and economic features of each site. The present article seeks to compare selected case studies in which sustainable management strategies have been considered for the conservation of rural settlements with an important vernacular heritage. The comparative analysis presented, identifies common strategies that can be replicated in sites with similar characteristics. The paper also provides a reflection and analysis on the potential of implementing these approaches in the conservation and management of the natural and cultural heritage of the Montesinho Natural Park, in Portugal

Assessment of the influence of horizontal diaphragms on the seismic performance of vernacular buildings

Preprint versionThe awareness and preservation of the vernacular heritage and traditional construction techniques and materials is crucial as a key element of cultural identity. However, vernacular architecture located in earthquake prone areas can show a particularly poor seismic performance because of inadequate construction practices resulting from economic restraints and lack of resources. The horizontal diaphragms are one of the key aspects influencing the seismic behavior of buildings because of their major role transmitting the seismic actions to the vertical resisting elements of the structure. This paper presents a numerical parametric study adopted to understand the seismic behavior and resisting mechanisms of vernacular buildings according to the type of horizontal diaphragm considered. Detailed finite element modeling and nonlinear static (pushover) analyses were used to perform the thorough parametric study aimed at the evaluation and quantification of the influence of the type of diaphragm in the seismic behavior of vernacular buildings. The reference models used for this study simulate representative rammed earth and stone masonry vernacular buildings commonly found in the South of Portugal. Therefore, this paper also contributes for a better insight of the structural behavior of vernacular earthen and stone masonry typologies under seismic loading.- The work presented in this paper was partly financed by FEDER funds through the Competitivity and Internationalization Operational Programme-COMPETE and by national funds through FCT-Foundation for Science and Technology within the scope of the project POC1-01-0145-FEDER-007633. This work was also financed in the framework of the Portuguese Public Procurement Code, LOTE 3EC5-Escola Secundaria da Anadia e Gafanha da Nazare