Artigos de Revista

Long-term durability of a structural adhesive joint is an important requirement, because it has to be able to support the required design loads, under service conditions, for the planed lifetime of the structure. One way of improving bond durability is through the use of surface treatments prior to bonding, which will activate the adherends' surface, making it more receptive to the adhesive. In this study, the effects of two surface pre-treatments (corona discharge and flame ionization) on three timbers (maritime pine, iroko, and European oak) were evaluated quantitatively through contact angle measurements. These measurements allowed the determination of the changes in the timber surface thermodynamic characteristics, thus indicating which pre-treatment performed better. The results showed that both techniques increased each timber's surface free energy, which could translate into a durability enhancement of bonded joints. Overall, the corona-discharge treatment looks more promising, since this treatment leads to a bigger increase in the timber's surface energy, especially in its polar component, whilst also tended to be less species specific, less susceptible to variation, and the treatment effects lasted longer for this type of treatment.

Digital preservation aims at maintaining digital objects accessibleover long periods of time, ensuring the authenticity and integrityof these digital objects. In this paper, we propose three differentapproaches to address the digital preservation problem. First, wesurvey the main requirements specific to the preservation arena.Next, we show how digital preservation can be approached as aspecific case of System of Systems Engineering. Then, weintroduce Enterprise Architecture as a framework which isregularly used to assist information systems design andmaintenance, but can also be applied to System of Systems andconsequently to digital preservation. Finally, in such complexenvironments, Risk Management is a key factor to assure thenormal behavior of systems along time. Thus, we propose a RiskManagement based approach to design and assess digitalpreservation environments, enclosing the definition of context andrequirements, and the identification of threats and vulnerabilities,to be used as the basis of the definition of actions to deal with therisks associated with those threats and vulnerabilities. Wegeneralize and survey the threats, vulnerabilities and techniquesthat can be applied in the scope of digital preservation.

This paper discusses the relationship between the age and the degree of deformation of Portuguese granites used as aggregates and the occurrence of alkali-aggregate reactions in concrete. Granitic rocks are an important source of crushed aggregates for concrete in Portugal. The existing quarries are situated in a variety of granite types, most of them emplaced during the Hercynian orogeny. Field experience shows that in Portugal some granitic rocks behave innocuously when applied in concrete, whereas others react deleteriously. A better knowledge of the properties that control the potential alkali-reactivity of granitic rocks in Portugal is therefore essential to improve the quality of new structures. Five granites with different Hercynian ages were studied in order to correlate their geological history with the mineral composition and texture. Especial focus was given to the deformation features of the silica minerals. Laboratory tests for the determination of the potential alkali reactivity were also performed. Additionally, the expected performance of the granites as aggregates, based on laboratory test methods, was compared to their behaviour when applied in real structures. Three concrete structures, two dams and one bridge, were inspected in order to detect signs of deterioration. In places where deterioration was found samples of reaction products and samples of concrete were collected for further characterisation in laboratory. Through the evaluation of the petrographic characteristics of the granites and the assessment of their behaviour in real concrete structures it was verified that, as a general rule, in Portugal the older granites are more likely potentially alkali reactive than the younger granites. Nevertheless, the geologic history of the rock cannot be neglected since regional tectonic episodes can have a great influence in the deformation features of the rocks.

Nesta comunicação, avalia-se o desempenho dos modelos COBRAS-UC e COULWAVE na simulação darebentação de ondas sobre um perfil barra-fossa, caso de teste estudado experimentalmente. Os resultadosnuméricos de ambos os modelos são comparados com os resultados experimentais, no que se refere à elevaçãoda superfície livre e às velocidades horizontais ao longo do canal. É também realizada uma análise no tempo,espectral e estatística de modo a caracterizar o desempenho dos modelos e a sua capacidade na simulação dosefeitos não lineares. Para o modelo COBRAS-UC é efectuada a caracterização do perfil de velocidades aolongo da coluna de água e comparada com os dados experimentais.

Uma das principais aplicações da caracterização da reflexão em hidráulica marítima através decoeficientes está associada aos modelos numéricos de propagação da agitação, queconstituem ferramenta fundamental para a modelação e previsão dos fenómenos físicosrelevantes na zona costeira. Todavia, a sua utilização ainda apresenta limitações,nomeadamente na definição dos parâmetros necessários para a caracterização das estruturase respectivas condições de fronteira.Na modelação da propagação de ondas em águas pouco profundas, surge a necessidade dequantificar com rigor os parâmetros de reflexão nas fronteiras do domínio, uma vez que estescondicionam as soluções estudadas.Neste trabalho, procede-se à avaliação do desempenho de várias formulações apropriadaspara quantificar a reflexão nas fronteiras duma bacia portuária da costa portuguesa

Nas últimas décadas, a importância da aplicação de ensaios não-destrutivos em diversas áreas da engenharia civil tem vindo a aumentar, principalmente no que concerne os métodos baseados na propagação de energia electromagnética de alta frequência, geralmente designada como Radar de Prospecção (RP) ou Ground Penetrating Radar-GPR (na literatura em Inglês). O Radar de Prospecção é uma ferramenta de levantamento geofísico que pode ser usada em vários domínios, como a geologia, engenharia civil, minas e meio ambiente.Sua aplicação consiste na detecção e localização de estruturas do subsolo, através da detecção de variações nas propriedades electromagnéticas do meio, que dependem da composição do material, (solo, rocha, betão, etc.), do teor em água e da densidade do material. No sector das infra-estruturas de transportes, como pavimentos rodoviários e aeroportuários, o conhecimento do tipo de estrutura e da espessura das camadas que constitui o pavimento é essencial para a avaliação da capacidade de carga, como um complemento aos resultados dos ensaios de carga. Neste contexto, o Radar de Prospecção (RP) é particularmente útil, pois é capaz de fornecer informações de forma contínua.Vários estudos sobre avaliação de pavimentos rodoviários e aeroportuários com o RP com antenas suspensas foram realizados pelo Laboratório Nacional de Engenharia Civil (LNEC) de Portugal, na última década. A experiência acumulada pelo LNEC no domínio da aplicação deste equipamento mostrou que, apesar do RP ser uma ferramenta valiosa, tem algumas limitações.A fim de optimizar a aplicação deste equipamento, é importante conhecer essas limitações e adaptar as metodologias de ensaio e de análise dos resultados às condições específicas do estudo a realizar.No presente artigo descreve-se a metodologia adoptada nesses estudos, apresentam-se alguns casos de estudo da aplicação do equipamento de radar de prospecção, e referem-se algumas das dificuldades inerentes à utilização do radar, juntamente com recomendações visando a optimização da sua utilização.

A partir da experiência de apoio e consultoria ao Projecto Velhos Guetos, Novas Centralidades (apoio: Fundos Europeus EFTA), desenvolvido no Bairro Social das Alagoas (Peso da Régua) e em Rabo de Peixe (S. Miguel/Açores), ambos em Portugal, discute-se sobre os procedimentos técnico-metodológicos aplicados com vista a contribuir para a (re)configuração de territórios tidos como periféricos, carenciados ou problemáticos. Observa-se que, no plano da prática, algumas das dificuldades a ultrapassar se relacionaram com modelos pré-concebidos de programação, planeamento e actuação no território, nomeadamente no que respeita ao colocar em acção um propósito integrador das dimensões sociais e urbanísticas. Defende-se a importância em se clarificar os significados práticos de um processo de intervenção socio-urbanística.

The environmental and economical consequences of an oil spill near coastal areas lead to an increasing effort by governments and the oil industry to develop tools, such as oil spill modeling systems, that could be used to mitigate these types of catastrophes. Oil spill modeling systems simulate hydrodynamics and the physical, chemical and biological processes that determine the fate of oil slicks. Recent technological developments, such as PC clusters, make these systems extremely attractive for practical applications in support of accident prevention and mitigation measures. This paper introduces a new oil spill modeling system and describes its application to the Prestige disaster (Northeast of the Iberian Peninsula, November 2002). The modeling system includes a flexible oil spill model, which can be used as a 2D surface plume model, or as a sophisticated surface-water column 3D model. Both options include all relevant processes, including the coastal retention and later release of the oil to the water column. The oil spill model is based on Eulerian-Lagrangian formulations, uses unstructured grid discretizations and is coupled with the 3D hydrodynamic model SELFE. A hindcast simulation of the Prestige oil spill disaster between 13 and 19 of November 2002 is presented here, based on the CEDRE information for ship route. The 3D hydrodynamics in the Iberian Atlantic shelf were determined with SELFE, forced by tides, wind and baroclinic gradients, while the 2D surface plume model was used to simulate the surface oil slick trajectory. The boundary and initial conditions for salinity and temperature were obtained from LEVITUS atlas while wind and wave data were retrieved from NCEP and WAVEWATCH III databases (NOAA, US). The oil plume trajectory validation was made against available satellite SAR images. The application shows the good numerical behavior of the model, its ability to predict the plume trajectory, and reveals its potential as a management tool. The application also highlights the importance of the accuracy of the forcings on the plume's pathway.

The necessity for inspection and assessment of glued laminated timber structures in service has raised interest in the evaluation of the glue lines. Glue line spectra were analysed and are discussed in detail with respect to spectral contributions from the adhesive, the hardener, the wood lamella below the adhesive, the curing temperature as well as ageing-related spectral changes. The combination of near infrared (NIR) spectroscopy and principal component analysis (PCA) allowed distinguishing between aged and non-aged samples and different copper azole preservative treatment levels of phenol-resorcinol-formaldehyde (PRF) glue lines. NIR-based partial least squares (PLS) regression modelling was performed for the glue line shear strength and for the curing temperature. These findings show that NIR spectroscopy is a fast and useful technique to evaluate the degradation on the PRF glue lines of untreated and copper azole treated laminated timber.

Pretende-se analisar aspectos condicionantes da vida útil de ancoragenscom base em cavilhas plásticas, com parafusos metálicos, aplicadas em edifíciosrecentes designadamente, em elementos de betão e de alvenaria de blocosmaciços de betão ou cerâmicos. Abordam-se, em particular, os casos deancoragens sujeitas a cargas de tracção e/ou de corte induzidas por elementosnão-estruturais fixados por essas ancoragens.