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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The paper presents an experimental program on a 5 storey structural wall physical model performed in LNEC 3D shaking table, in Lisbon, within the Project ECOLEADER-LIS. The characteristics of the reduced model and the test set-up are described, as well as the analysis of the main experimental results. Furthermore the results of numerical simulations are discussed. These tests had the main purpose of studying and evaluating the seismic resistance of thin lightly reinforced structural walls representative of the Central Europe practice. Particular issues have been adressed: (a) To investigate the influence of simultaneous 3D loading conditions. (b) To study walls with T (H) cross-sections. (c) To investigate the free edge of a T (H) shaped walls in compression and different trypes of confinement. (d) To investigate the behaviour of coupled walls and the behaviour of diagonally reinforced coupling beams in thin walls. (e) To calibrate and further develop numerical models. Inelastic dynamic analysis was also performed using Multiple-Vertical-Line-Element-Model (MVLEM), which was extended into 3D and implemented into OpenSees. This macro model proved the ability to simulate and predict the global behavior of the wall as well as the behavior of confined boundary areas and local extensions of longitudinal reinforcement. Considerable overstrength was observed in the wall with minimum reinforcement. However, its deformation capacity was limited to less than 1% of the height. Relatively thick slab enhanced the strength of thin coupling beams considerably. Consequently, they did not perform as expected in capacity design and high axial forces as well as shear failure were induced into the wall piers. The EC8 confining reinforcement proved to be efficient. Simpler details (i.e. U-shaped stirrups) might be acceptable for low walls (5-storey) and/or in the case of low seismic intensity. Sequence of loading and pre-cracking influenced the response considerably. The influence of bi-axial loading was relatively low.

In the process of preservation of ancient masonry structures, damage evaluation and monitoring procedures are particularly attractive, due to the modern context of minimum repair and observational methods, with iterative and step-by-step approaches. High-priority research issues related to damage assessment and monitoring are global non-contact inspection techniques, sensor technology, data management, diagnostics (decision making and simulation), dynamic (modal) analysis, self-diagnosing / self-healing materials, and prediction of early degradation. On these concerns, the present paper aims to assess damage in masonry structures at an early stage. Replicates of historical constructions were built in virgin state. Afterwards, progressive damage was applied and modal identification analysis was performed at each damage stage, aiming at finding adequate correspondence between dynamic behavior and internal crack growth. Accelerations and dynamic strains were recorded in many points of the replicates. Comparisons between different techniques based on vibrations measurements are made to evaluate different damage identification methods.

This work uses a non-stationary stochastic seismological model, based on random vibration theory, for calculating response spectra and synthesizing strong ground motion acceleration records for Portugal Mainland. The validation of the method and comparison with strong ground motion records for Portugal are entirely carried out in terms of 5% damped pseudo absolute response spectra for acceleration. The calibrated model is used to simulate ground motion acceleration for the 1755 Lisbon earthquake. Five potential source rupture models that have been recently proposed by several authors for the 1755 Lisbon earthquake are tested: two analytical models based on hydrodynamic studies; two models based on seismic surveys and on from a recent suggestion based on induced stress changes.For all models, peak ground acceleration maps are compared with iso-intensities map of the earthquake in order to test the ability of the source models for estimating the intensities of the earthquake. The peak ground motion is calculated for different unknown parameters like the rupture velocity, the slip distribution and the nucleation point. The fault parameters like dimension, dip and strike are the ones proposed by the authors of the different analysed source models

This paper presents a dynamic identification analysis of a masonry construction, built to be tested in

In the framework of the ongoing European project

En este trabajo se confirma experimentalmente una nueva formulación del problema de los bloques rígidos sometidos a vibraciones externas. Un estudio sistemático de las respuestas del sistema permite determinar los valores de los parámetros relevantes. La nueva formulación hace más sencilla la implementación de técnicas computacionales para el problema da varios tipos de mecanismos acoplados. En las respuestas analizadas, tanto para régimen libre como forzado, se ha observado un buen acuerdo entre teoría y experimento.

This work presents a non-stationary stochastic seismological model, based on random vibration theory. The model is applied to the 1755 Lisbon earthquake, being a tentative of reproducing the input motion of this severe earthquake. Five possible interpretations of the fault source mechanism, recently proposed by several authors for the 1755 Lisbon earthquake, are analyzed. Three interpretations are based on seismic surveys and two from a suggestion based on induced stress changes. In order to test the feasibility of the different proposed fault source mechanisms to reproduce the historical intensities of the earthquake, ground motion maps were obtained at bedrock level and the degree of the interrelationship between some seismic parameters and the intensities of the earthquake aredescribed by a correlation analysis.

The objective of the present paper is to present the new LNEC automatic Seismic Scenario Loss estimate methodology (SSL), integrated on a Geographic Information System (GIS), which comprises modules evaluating bedrock seismic input, local soil effects, vulnerability and fragility analysis and human losses analysis.Results of seismic risk scenarios studies for the Metropolitan Area of Lisbon are presented.

Este trabalho foi realizado no âmbito do projeto Dynaseis POCTI 36071-2000, cujos objetivos principais são: i) a determinação experimental de frequências próprias e modos de vibração de uma estrutura em betão armado localizada no Parque das Nações em Lisboa; ii) a elaboração do modelo numérico da estrutura e a sua comparação com os resultados experimentais; iii) a avaliação do comportamento da estrutura sob ação sísmica. Neste estudo apresentam-se os resultados dos ensaios experimentais e a comparação com o modelo numérico de elementos finitos (FEM). O edifício escolhido foi a torre da Portugal Telecom

Neste trabalho apresentam-se resultados com os quais se pretende mostrar que atualmente já é possível caracterizar o comportamento dinâmico de grandes barragens de betão (frequências próprias e modos de vibração) com base na medição das vibrações ambiente, ou induzidas pelas atividades de exploração. Para tal é importante utilizar instrumentação adequada e uma estratégia de análise e interpretação das medições baseada na utilização conjunta de diferentes metodologias de identificação modal e de resultados de modelos numéricos que permitam simular o comportamento dinâmico do sistema barragem-fundação-albufeira. Este objetivo só pode ser conseguido com uma monitorização em contínuo, a qual permitirá também obter a resposta da estrutura a eventuais ações sísmicas

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