Publications

An innovative higher-order beam theory, capable of accurately taking into account flexural

The specific features of the proposed force-based formulation derived in the companion paper, which is applied for the first time to higher-order beam theories, are herein thoroughly validated. Introductory numerical examples illustrate the influence of mesh refinement, boundary conditions, and slenderness ratios for isotropic linear elastic response. Specific higher-order effects

An accurate assessment of the airflow in naturally ventilated double skin facades (DSF) is crucial for a correct design and performance evaluation. Measuring and predicting DSF airflow is not a straightforward task, given the stochastic nature of the wind, which can assist or oppose the buoyancy force. The present paper resumes the results of airflow measurements inside a naturally ventilated double skin facade using a tracer gas technique. The tests were performed on an outdoor air curtain (OAC) DSF test cell with a movable slat venetian blind. Measurements with no active shading and at night were also performed. Outdoor and test cell air gap temperatures were continuously measured and wind pressure coefficients were determined from wind tunnel tests. Experimental results were then compared to those obtained by a simple model taking into account both thermal and wind effects on the facade. From this comparison discharge coefficients were estimated, which can be used for characterizing the DSF behaviour.

The existing building stock in Azores islands (Portugal) was severely damaged during 1980and 1998 earthquakes. Structural failure was probably caused by a combination of factorsthat are not yet well understood. Earthquake source characteristics, site effects and structuralvulnerability may be some of those factors. However, it is very difficult to assess theinfluence of each factor on structural failure, mainly because recorded accelerograms usedin nonlinear structural analysis are influenced by both source characteristics and site conditions.The only way to overcome this problem is to control each factor individually whichcan be done by using simulated accelerograms. In our previous work, stochastic groundmotion simulations results were compared with earthquake records. Results seem to indicatethat simulated accelerograms can match recorded accelerograms if proper sourcecharacteristics and geological site conditions are selected. In this work, simulated accelerogramswere used for seismic nonlinear structural analysis. Simulations were carried outconsidering several 1980 Azores earthquake possible sources and for different geologicalsite conditions. Simulated accelerograms were then used to evaluate the structural nonlinearbehaviour of a reinforced concrete structure and of two masonry structures. The resultsof this work highlight the importance of site conditions and earthquake source characteristicsto the determination of the design seismic actions of Azores islands. This work wasperformed in the scope of

O Laboratório Nacional de Engenharia Civil tem uma longa experiência na área da Engenharia Sísmica, sendo uma das instituições de referência, a nível europeu, em todos os campos desta área das Ciências da Engenharia. A investigação europeia em Engenharia Sísmica teve início no final da década de 50, tendo sido o LNEC, na pessoa do Engenheiro Júlio Ferry Borges, o seu principal impulsionador. Desde então, assistiu-se ao estudo dos diferentes aspetos da fenomenologia ligada à caraterização da ação sísmica e ao comportamento das estruturas sujeitas à ação dos sismos, como ilustrado pelas cerca de 50 teses de mestrado e doutoramento nos diferentes domínios da Engenharia Sísmica, desenvolvidas no Núcleo de Engenharia Sísmica e Dinâmica de Estruturas (NESDE), nas duas ultimas décadas, e por mais de uma centena de investigadores visitantes, nacionais e estrangeiros. No âmbito da avaliação do risco sísmico, o LNEC tem tido um papel fundamental a nível nacional, assumindo a liderança da investigação científica nas matérias relacionadas com a perigosidade sísmica, a caraterização da ação sísmica, a avaliação do risco, e o desenvolvimento de estratégias para redução da vulnerabilidade sísmica...

This paper aims to assess and improve the seismic performance of an existing masonry building withflexible floors, representative of a Portuguese building typology

The energy dissipation capacity of the NiTi alloy was evaluated as part of a series of shake table tests. A superelastic damper was developed to take advantage of the hysteretic energy dissipation associated with this type of shape memory alloy. Each device was tested at different intensity levels. A vertical steel cantilever with 600 kg mass on top was subjected to a series of ground motions with different spectral characteristics. The dampers were placed as part of a tie system, restraining the horizontal movement of the top mass. The devices showed stable hysteretic behavior allowing for energy dissipation.

In this paper we provide an overview of recent research work that contributes to clarify the effects of non-linear dynamic interaction on the seismic response of soil foundation-superstructure systems. Such work includes experimental results of seismically loaded structures on shallow foundations, theoretical advancements based on improved macro-elementmodeling of the soil-foundation system, examples of seismic design of bridge piers considering non-linear soil-foundation interaction effects, and numerical results of incremental non-linear dynamic analyses. The objective of this paper is to support the concept of a controlled share of ductility demand between the superstructure and the foundation as a key ingredient for a rational and integrated approach to seismic design of foundations and structures.

This paper is focused on the study of an earthquake protection system, the tuned liquid damper (TLD), which can, if adequately designed, reduce earthquake demands on buildings. This positive effect is accomplished taking into account the oscillation of the free surface of a fluid inside a tank (sloshing). The behaviour of an isolated TLD, subjected to a sinusoidal excitation at its base, with different displacement amplitudes, was studied by finite element analysis. The efficiency of the TLD in improving the seismic response of an existing building, representative of modern architecture buildings in southern European countries was also evaluated based on linear dynamic analyses.

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A utilização de dispositivos de dissipação de energia é atualmente vista como uma forma eficiente para proteger estruturas contra ações sísmicas. Um número considerável deste tipo de dispositivos tem vindo a ser instalados um pouco por todo o mundo. Muito recentemente dispositivos do tipo Tuned Liquid Dampers (TLD) tem despertado a atenção da comunidade científica internacional como forma simples mas eficaz para reduzir a resposta de edifícios quando sujeitos a ações dinâmicas.Os TLDs são tanques com água, com relações entre comprimento e altura de água tais que a sua frequência natural quase que se ajusta à frequência natural da estrutura cuja amplitude se pretende mitigar. A energia de vibração do edifício é transferida para a água em movimento (sloshing) onde se dissipa. Os princípios básicos de funcionamento são semelhantes aos observados para os Tuned Mass Dampers (TMDs), com a vantagem da instalação ser muito mais fácil e económica. Tanto TLDs como TMDs apresentam bom desempenho para estruturas flexíveis, de frequências naturais pouco elevadas.Em Portugal, devido principalmente à reduzida altura das construções, este tipo de dispositivos não é muito conhecido ou utilizado. Não obstante isso as construções Portuguesas modernas tem uma tendência natural para se tornarem mais flexíveis sendo portanto previsível que o uso de TLDs se torne uma boa opção para redução dos deslocamentos horizontais sofridos pelas estruturas, atendendo aos custos reduzidos associados à construção, colocação e manutenção destes dispositivos. O artigo descreve o estudo experimental sobre TLDs iniciado em Bristol (U. Bristol) e em continuação no LNEC, apresentando alguns dos resultados preliminares obtidos.

The present paper aims to explore damage assessment in the masonry structures at an early stage by vibration measurements. Two replicates of historical constructions were built in virgin state: one arch with 1.5 m span and one shear wall with 1.0 m2. Afterwards, progressive damage was applied and sequential modal identification analysis was performed at each damage stage, aiming to find adequate correspondence between dynamic behavior and internal crack growth. Accelerations and strains in many points were record in the replicates. Eigen frequencies, mode shapes and modal strains were derived from the dynamic measurements. Environmental effects of the temperature and relative humidity on the dynamic response were studied. A first updating process was performed on the results of the undamaged arch to tune a finite element model. Moreover, the tests were repeated with added masses to scale the mode shapes. Finally, a brief analysis of the results of the several damage scenarios are presented in the paper.

This paper concerns to the post-occupancy monitoring of a building sited in Lisbon with transparent double-skin façades (DSF). This is the first of an enlarged monitoring program covering other buildings and weather conditions aiming to clarify under which climate and performing conditions this architectural solution is acceptable. Within this campaign an enlarged set of parameters were measured, covering from outdoor conditions to indoor comfort. The present paper focus is the thermal behaviour of the façade.

This paper studies the dynamic behaviour of rigid-block structures under seismic behaviour. For this purpose, an experimental investigation has been carried out on the rocking response of single blocks, and ensembles of two and three blocks structures. These structures were subjected to three different base motions: free rocking, harmonic and random excitations. The tests were performed at the seismic table of the National Laboratory of Civil Engineering (LNEC) of Portugal.

Esta comunicação descreve os ensaios sísmicos efetuados no LNEC a uma estrutura pré-fabricada de betão armado. Os ensaios foram desenvolvidos com o apoio da Comissão Europeia e no âmbito do projeto de investigação PRECAST STRUCTURES EC8

Much work in Earthquake Engineering was devoted to the improvement of earthquake resistant design of new structures. In several years EN 1998 will be the main seismic code for all European countries. But it is well known, that in many large earthquakes older existing structures cause much more casualties and damages than new structures. It is certainly not possible to retrofit all existing structures, but agreement exists, that assessment and retrofit of safety - critical

Earthquake scenarios are used in different activity domains like: civil protection disaster preparedness, computing overall seismic losses for a portfolio, or evaluating time histories and ground motion duration to be used in seismic design. However, the choice of an earthquake scenario is often based on deterministic arbitrary assumptions, like the region worst historical event reported. The purpose of this work is to overcome the disadvantages of a deterministic approach, in what concerns the choice of earthquake scenarios in Portugal. For each of the 278 Portuguese counties, a scenario ground motion based on a probabilistic seismic hazard disaggregation analysis is evaluated. Portuguese probabilistic seismic hazard analysis is reviewed in order to perform its disaggregation. Probabilistic seismic hazard was disaggregated considering different spaces of random variables. Bivariate conditional hazard distributions in X-Y (seismic source latitude and longitude) are analyzed, as well as multivariate conditional hazard distributions in M-R-

This paper describes and analyses the results of the seismic tests preformed at LNEC in a RC precast structure which is representative of a Portuguese system. This type of precast construction is used mainly for industrial buildings and was designed and constructed by a precast company with their common practice. The precast system can be considered as jointed with dry connections of limited ductility. A scaled 1/3 specimen was tested on LNEC

With the purpose of assessing the seismic behaviour of a reinforced concrete building structure non-seismically designed, an experimental study was carried out at the LNEC/Lisbon shake table, within the framework of the European project SPEAR. The tested structure was a simplification of a 3-storey building, irregular in plan, representative of older construction in southern Europe, without engineered earthquake resistance. It was designed for gravity loads alone, using the concrete design code used in Greece between 1954 and 1995, with construction practice and materials commonly used in southern Europe in the early 70

This paper describes the shaking table tests of an asymmetric limestone masonry building, under different reinforcement conditions. The work was performed in the aim of the project

This book presents a selection of the best papers from the HEaRT 2015 conference, held in Lisbon, Portugal, which provided a valuable forum for engineers and architects, researchers and educators to exchange views and findings concerning the technological history, construction features and seismic behavior of historical timber-framed walls in the Mediterranean countries. The topics covered are wide ranging and include historical aspects and examples of the use of timber-framed construction systems in response to earthquakes, such as the gaiola system in Portugal and the Bourbon system in southern Italy; interpretation of the response of timber-framed walls to seismic actions based on calculations and experimental tests; assessment of the effectiveness of repair and strengthening techniques, e.g., using aramid fiber wires or sheets; and modelling analyses. In addition, on the basis of case studies, a methodology is presented that is applicable to diagnosis, strengthening and improvement of seismic performance and is compatible with modern theoretical principles and conservation criteria. It is hoped that, by contributing to the knowledge of this construction technique, the book will help to promote conservation of this important component of Europe

The applications of discrete elements models based on rigid block formulations to the analysis of masonry walls under horizontal out-of-plane loading is simplified block pattern are addressed. Two procedures for creating irregular block systems are presented, one using Voronoi polygons, the other based on a bed and cross joint structure with random deviations. A test problem provides a comparison of various regular and random block patterns, showing their influence on the failure loads. The estimation of manual frequencies of rigid block models, and its application to static pushover analyses, is addressed. An example of application of rigid block model to wall capacity problem is presented.

The overall aim of Sub-Project 10 (Earthquake disaster scenario predictions and loss modelling for urban areas) has been to create a tool, based on state-of-the-art loss modelling software, to provide strong, quantified statements about the benefits of a range of possible mitigation actions, in order to support decision-making by urban authorities for seismic risk mitigation strategies. A further larger aim has been to contribute to a seismic risk mitigation policy for future implementation at European level. Among the European cities for which loss estimation studies have been carried out are Istanbul, Lisbon and Thessaloniki, and tools, using GIS mapping, have been developed by research teams in each of these cities; these were made available for further development to examine mitigation strategies within SP10. Related research studies

Much work in Earthquake Engineering was devoted to the improvement of earthquake resistant design of new structures. One European result is EN 1998, which will be in several years the main seismic code for all European countries. But it is well known, that older existing structures cause in many large earthquakes much more casualties and damages than new structures. It is certainly not possible to retrofit all existing structures, but agreement exists, that assessment and retrofit of safety - critical - structures and lifeline structures must have priority. In September 2004 the European Integrated Research Project LESSLOSS on Risk Mitigation for Earthquakes and Landslides was started. The project will run for three years and comprises 13 Sub-Projects (SP´s). The consortium consists of 46 partners (see http:\\www.lessloss.org). LESSLOSS SP5 is on In-situ Assessment, Monitoring and Typification of buildings and Infrastructure. The project partners of SP5 are ARS, CESI, LNEC, RWTH and VCE. This Sub Project focuses mainly on the assessment of important existing structures and tries to integrate experimental methods into the assessment procedure. The progress of SP5 obtained in the first year is summarized in this paper. Highlights presented by all partners are mentioned and the assessment of Hospital Innsbruck is presented in more detail. The most innovative task of LESSLOSS/ SP5 is Update of vulnerability estimates via monitoring, which was also started in the first year.

In order to study the behavior of bridge structures in relation to traffic, wind and seismic loads, it is extremely important to know their actual dynamic properties (natural frequencies, vibration mode shapes and damping). The experimentally identified dynamic properties of bridge structures are also an effective way to characterize their actual global structural behavior. Whether included in the reception load tests of recently built bridges, before they are opened to the traffic, or as part of the inspection works of bridges already in service, LNEC has performed modal analysis studies based on the results of ambient vibration tests. Some of the studies carried out recently in important bridges are reported in this paper.

O sismo de Northridge ocorreu na parte norte da área metropolitana de Los Angeles, Califórnia, às 4:31 h do dia 17 de janeiro, uma segunda-feira coincidente com dia de feriado nacional, tendo atingindo uma magnitude de 6.6 na escala de Richter. O número total de vítimas mortais cifra-se em 57, havendo para cima de 8 000 feridos e 20 000 desalojados.As estimativas de perdas totais, feitas em meados de fevereiro de 1994, apontavam para valores de 15 biliões de US dólares, tendo o Estado da Califórnia apresentado um impacto económico total de ordem dos 30 biliões de dólares, perto do valor do Orçamento Geral do estado Português para 1994. Os prejuízos infligidos na indústria e no comércio são também surpreendentemente elevados, exigindo longos períodos de interrupção das atividades económicas.

Communicating science within disaster risk reduction using methods that encourage two-way dialogue between scientists and laypersons is a challenging task. This paper aims at presenting a methodological strategy of communicating risk and non-structural seismic protection measures through participatory approach. Such methodological strategy is part of a pilot experience of risk communication in two schools in Lisbon (Portugal) under the EU project KnowRISK (Know your city, Reduce seISmic risK through non-structural elements). The efficacy of education for seismic safety is often inhibited by an incomplete understanding of the process by which individuals decide to protect themselves from harm (Becker JS, Paton D,Johnston DM, Ronan KR. Nat Hazards 64(1):107

Most of the Lisbon 18th century timber-framed masonry

Good performance of non-structural elements can be decisive in saving lives and costs when an earthquake strikes. The European project KnowRISK aims to educate and encourage households to take the necessary precautionary measures to protect people, houses, and contents. Preparedness and prevention act on community resilience. Within the KnowRISK project, the idea of a Practical Guide has been conceived suggesting seismic mitigation solutions for non-structural components to non-experts stakeholders. It is intended to guide people into the first steps of prevention in a straightforward manner, minimizing or avoiding injuries, damage, and long-term financial consequences. The novelty of the Guide belongs to his philosophy: a path through increasing challenges corresponds to a growing level of safety. The idea is that anyone can mitigate seismic risk in its own environment by adopting simple and low cost measures. The Practical Guide may contribute to increase risk awareness. This kind of initiatives if undertaken at larger scales may also enhance social resilience.

When one of the dimensions of a structural member is not clearly larger than the two orthogonal ones, engineers are usually compelled to simulate it with refined meshes of shell or solid finite elements that typically impose a large computational burden. The alternative use of classical beam theories, either based on Euler-Bernoulli or Timoshenko

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This text reflects the first of the four lectures that the author has presented at Udine, Italy, at CISM

Um dos principais problemas e interesses da engenharia sísmica é a caracterizaçãoda acção sísmica, envolvendo a estimativa da intensidade, conteúdo em frequência,duração e variabilidade espacial dos movimentos intensos do solo mais gravosos, emtermos dos seus efeitos nas estruturas, que pode ocorrer num local.O presente trabalho de investigação desenvolve e aplica a metodologia estocástica etécnicas de modelação de fonte

Os sismos são encarados frequentemente como desastres naturais inevitáveis. Todavia,deveriam ser considerados fenómenos naturais, cujos efeitos adversos podem ser minimizadoscaso se proceda a uma gestão efectiva do risco sísmico.O objectivo principal do presente trabalho de investigação é o de avaliar o risco sísmicoem Portugal Continental.Sendo um tema de natureza multidisciplinar, apresentam-se e discutem-se modelos deavaliação probabilística da perigosidade sísmica e sua desagregação, de vulnerabilidade efragilidade sísmicas de tipologias construtivas, de danos e de perdas económicas e humanas.Aplica-se a análise probabilística da perigosidade sísmica, e sua desagregação, aPortugal Continental, obtendo-se cenários modais capazes de reproduzir os níveis deperigosidade que os condicionam. Apresenta-se o inventário do parque habitacional e seushabitantes, descriminado por factores de vulnerabilidade, e classifica-se a sua vulnerabilidadesegundo os modelos de dano. Procede-se à actualização e aferição de uma metodologia parasimulação de cenários sísmicos, integrada num Sistema de Informação Geográfico. Avalia-seo risco sísmico, seguindo diversas abordagens, comparando-se os resultados com o risco deoutros países.Construiu-se assim uma ferramenta de avaliação de perdas devidas a sismos, queconstitui uma primeira contribuição para o desenvolvimento de um processo de gestão dorisco sísmico aplicado ao Continente Português.

O parque habitacional de Portugal Continental contém algumas tipologias construtivas deelevada vulnerabilidade sísmica em relação às quais urge actuar no sentido de reduzir o riscosísmico a elas associado. No projecto de investigação

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This report addresses the National Laboratory for Civil Engineering (LNEC) participation in Subproject 10 Earthquake disaster scenario predictions and loss modelling for urban areas. More precisely this report was developed in order to accomplish the 24 months LESSLOSS deliverable nº 85, which achieves loss estimates for the Metropolitan Area of Lisbon (MAL), for pre-defined scenarios earthquake. These loss estimations represent the reference situation to be compared with revised loss estimates after implementing mitigation actions with the ultimate goal of being established, in the next deliverable, the

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The present report describes the construction of a model in limestone masonry for the user Group 3 oh the ECOLEADER Project, led by IRIDEX Construction Group, and the first phase of the experimental program developed in LNEC. The description of the construction, a photographic report and the results obtained on the characteristics tests made on the mortars used in the construction are presented.The construction was carried out by contractor José dos Santos Paixão on the basics of model details and materials specifications proposed by the User group 3, being NESDE/LNEC responsible for the guidance and supervision of the works.

This report describes the first phase activity of the Portuguese group in the Precast Structures EC8 research projet. The Portuguese group is composed by Laboratório Nacional de Engenharia Civil (LNEC) and the Civibral, S.A. Precast Company.In this phase, seismic test were made in the LNEC

The present report addresses the first twelve months of LNEC participation in LESSLOSS

The dynamics of rigid bodies was studies by long time, because this phenomenon is important in the seismic security of some types of structures. However, there are few experimental studies. This job shows the experimental test carried out at the Laboratório Nacional de Engenharia Civil (LNEC) of Portugal. Four blue granites stones were tested, each one with different geometrical characteristics, under harmonic and random motions.A numerical simulation was carried out with the Discrete Element Method (DEM). This method has shown to be a good tool in the study of the dynamics of rigid bodies. It was proposed a new methodology to find the parameters of the DEM by using the parameters of classical theory.

The project LESSLOSS

Análise dos registos históricos de eventos climáticos e o seu impacto no setor da energia da AML, para identificar o grau em que este setor foi afetado por estímulos relacionados com o clima. Avaliação de capacidades adaptativas.

Análise da forma das edificações nas ações do vento

As condicionantes arquitetónicas e de urbanização na ventilação natural

Caracterização do vento. Ações sobre estruturas. Ensaios em túnel de vento