Publications

The boundary layer concept is applied to the flow around the nose of a streamlined train. In general, that flow is not axisymmetric due to the shape of the nose and the crosswind component of the relative incoming velocity. This departure from axisymmetry produces a transverse pressure gradient that is responsible for skewing an otherwise plane boundary layer. An empirical correlation, dependent on the longitudinal velocity and one unknown parameter, is used to represent the transverse velocity profile. The value of that unknown parameter is obtained from the momentum equations integrated streamwise inside the boundary layer. A visual comparison was carried out between the numerical simulations and the skin shear pattern of a scale model in a wind tunnel. The qualitative results compare well, the numerical model being able to locate the position of the main longitudinal vortices on the lee side of the train.

Masonry buildings worldwide exhibited severe damage and collapse in recent strong earthquake events. It is known that their brittle behavior, which is mainly due to the combination of low tensile strength, large mass and insufficient connection between structural elements, is the main limitation for their structural implementation in residential buildings. A new construction system for masonry buildings using concrete blocks units and trussed reinforcement is presented here and its seismic behavior is validated through shaking table tests. Dynamic tests of two geometrically identical two-story reduced scale (1:2) models have been carried out, considering artificial accelerograms compatible with the elastic response spectrum defined by the Eurocode 8. The first model was reinforced with the new proposed system while the second model was built with unreinforced masonry. The experimental analysis encompasses local and global parameters such as cracking patterns, failure mechanisms, and in-plane and out-of-plane behavior in terms of displacements and lateral drifts from where the global dynamic behavior of the two buildings is analyzed comparatively. Finally, behavior factors for the design recommendations in case of unreinforced masonry are also evaluated.

The out-of-plane response of walls in existing stone masonry buildings is one of the major causes of vulnerability commonly observed in post-earthquake damage surveys. In this context, a shaking table (ST) test campaign was carried out on a full-scale masonry façade mainly focusing on the characterization of its out-of-plane overturning behaviour. The structure tested on the ST is a partial reproduction of an existing building from Azores, damaged during the 9 July 1998 Faial earthquake. The definition of the tested specimen as well as the selection of the input ground motion is reported in this paper. A specific emphasis is given to the definition of the time-history to be applied during the tests because it was felt as an essential and crucial part of the work to obtain the desired overturning behaviour. The accelerogram to be imposed was selected from a large set of accelerograms (74) by means of a step-by-step procedure on the basis of several numerical analyses resorting to the rocking response of rigid blocks.

The present work describes a shaking table experimental campaign specifically developed for the characterisation of the out-of-plane response of a full scale stone masonry façade. After the description of the specimen and the selection of the input motion presented in a companion paper (Part 1), the experimental campaign is illustrated and extensively described. The out-of-plane behaviour of the sacco masonry façade is presented in terms of displacements, velocities, and accelerations recorded during the shaking table tests. A one-sided rocking response of the façade was observed prior to collapse. The impacts were clearly identified in the acceleration records. The façade overturning occurred with the expected failure mode, as predicted in the design of the test.Finally, some conclusions are drawn regarding the observed behaviour and particular features of this type of stone masonry constructions, which may influence the global behaviour of the façade.

During seismic action, energy dissipation in structures occurs in structural and non-structural components, as well as in the substructure. Several of these dissipative mechanisms are modelled explicitly in nonlinear dynamic analyses, notably through relatively sophisticated hysteretic finite elements. Nevertheless, in most practical applications, it is not possible to simulate all the physical contributions to energy dissipation.Structural engineers are thus constrained to overcome this limitation by a mathematical artifice, in the form of equivalent linear viscous damping, which accounts for the remaining

A utilização de dispositivos de dissipação de energia é vista como forma eficiente para proteger estruturas contra ações sísmicas. Os dispositivos Amortecedores de Líquido Sintonizados (ALS) são uma forma simples mas eficaz para reduzir a resposta de estruturas face a ações dinâmicas. Este artigo descreve simulações numéricas sobre o comportamento de ALS, isolados e/ou incluídos numa estrutura de transmissão, comparando-as com os resultados obtidos experimentalmente. Para o efeito foi usado um software de acesso livre denominado CLAWPACK com potencialidades para simular os fenómenos que ocorrem no interior de ALSs. O CLAWPACK consiste num conjunto de rotinas em Fortran desenvolvidas para obtenção de soluções numéricas de sistemas hiperbólicos de equações parcialmente diferenciais no tempo, como é o caso dos fenómenos não-lineares subjacentes à shallow water wave theory. Foram necessárias adaptações e ajustes em algumas das rotinas principais para permitir a simulação das excitações dinâmicas pretendidas. Nas simulações numéricas são variados alguns parâmetros, em que se incluem a altura de água, a amplitude de excitação e o número de dispositivos. Os principais resultados obtidos são comparados, com os resultados obtidos experimentalmente, tanto para dispositivos isolados como para dispositivos incluídos nas estruturas ensaiadas. As principais conclusões obtidas serão também apresentadas.

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As tubagens enterradas constituem componentes principais de sistemas que permitem assegurar o bem estar e o desenvolvimento da sociedade, nomeadamente no que respeita ao abastecimento de água, à drenagem de águas residuais, ao transporte de energia e à comunicação.Com a consolidação das malhas urbanas, tem-se assistido a uma crescente preocupação, não só com a construção, mas em especial com a fase de utilização desses sistemas, tanto nas atividades de exploração (operação e manutenção) como de fim de vida (reabilitação e substituição). Adicionalmente, existe um conjunto crescente de preocupações mais vasto do que as questões operacionais correntes, que inclui os efeitos de fenómenos naturais, como os sismos. As abordagens de gestão do risco permitem ter em conta estes fenómenos e lidar explicitamente com a incerteza que lhes está associada.No contexto da problemática da gestão do risco sísmico de tubagens enterradas, apresenta-se um levantamento de modelos para avaliação da respetiva vulnerabilidade. No âmbito deste artigo é proposta uma abordagem para incorporar a variabilidade probabilística na modelação da vulnerabilidade sísmica de tubagens enterradas. Os resultados obtidos com a metodologia proposta são comparados com a gama de variação da vulnerabilidade sísmica apresentada pela American Lifelines Alliance.

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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

A caracterização da ação sísmica, para efeitos de projeto e verificação de segurança das estruturas de engenharia civil, é realizada para valores de intensidade sísmica elevados quando comparados com os valores de intensidade sísmica sentidos frequentemente. Tais valores elevados são compatíveis com os níveis de segurança exigidos para as estruturas, que usualmente são considerados implícitos nas regras de dimensionamento e verificação de segurança de estruturas contempladas nos códigos em vigor.

O presente relatório, elaborado no âmbito do projecto de investigação para a Fundação para a Ciência e a Tecnologia intitulado

Os sismos são fenómenos naturais que apenas poderão ter consequências desastrosas se afetarem uma região habitada do globo. Sem dúvida que os piores efeitos de um desastre sísmico são as perdas de vida humana envolvidas.A redução das perdas de vidas humanas é assim um dos grandes objetivos das políticas de prevenção e proteção sísmica e do domínio de investigação da engenharia sísmica.Para se ter uma ideia da dimensão do problema refira-se que apenas no século XX (entre 1900 e o fim de 1992), o montante oficial de vítimas mortais em 1 100 sismos muito severos, atingiu o total de 1 528 000. Perto de metade deste número de vítimas ocorreu num único país, a China, e as principais contribuições para este.

O presente relatório, elaborado no âmbito do projeto de investigação PRAXIS XXI

O presente relatório, elaborado no âmbito do projeto de investigação para a Fundação para a Ciência e a Tecnologia intitulado

The present progress report describes the research developed by LNEC under the ENVIRONMENT project ENV4-CT97-0548, entitled

O presente estudo tem por objetivo apresentar uma metodologia para a avaliação dos efeitos da propagação das ondas sísmicas em condutas de água enterradas. Essa avaliação é efetuada em termos do campo de deformações (extensões axiais e curvaturas), a serem impostas nas condutas, para diferentes valores máximos de aceleração e velocidade da ação sísmica associados a diferentes períodos de retorno.A metodologia desenvolvida é aplicada à cidade de Lisboa considerando as características locais do terreno, diversos diâmetros de tubagens e ambas as situações de condutas contínuas ou com juntas.

As part of ECOEST European research activities, this report describes the experimental programme carried out at the new LNEC seismic simulator facility. It is reported a detailed characterization of the frequency response of the shaking table and the results from an assessment of its control fidelity. This information will act as a benchmark, against which the performance of future tests at this facility could be gauged.A part of the description of the procedures and results of the test programme carried out, it was also compiled descriptive material about the entire facility.

O presente relatório descreve os estudos efetuados no LNEC, que visaram o desenvolvimento e implementação computacional de um algoritmo representativo das relações histeréticas forças-deslocamentos generalizados observados em ensaios de elementos de betão armado sujeitos á flexão.Foi dado um carater geral à implementação do modelo, de forma a poder ser usado em trabalhos futuros de análise dinâmica em regime não linear de estruturas de betão armado, sujeitas á ação dos sismos.O algoritmo computacional resultante é suficientemente versátil uma vez que através da introdução de alguns parâmetros pode reproduzir diferentes comportamentos estruturais, tais como: degradação de rigidez e resistência, efeito de

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