Papers

The protection performance of varnishes applied to two different wooden substrates (maritime pine and iroko) for outdoor exposure was investigated for eight different varnish systems (with and without colorants and two different light stabilizers). All were subjected to accelerated artificial weathering and natural weathering. Several test methods were used to evaluate the appearance and physical-chemical properties of the coatings during the degradation. The results obtained lead to the selection of the best varnish formulation for the protection of wood for exterior use and provide useful evaluation of the test methods employed.

As inovações tecnológicas, nomeadamente nas áreas das tecnologias e sistemas de informação e do conhecimento colocam à disposição da sociedade ferramentas para o desenvolvimento de sistemas que podem contribuir de forma significativa para apoiar as actividades do controlo de segurança de barragens, através, nomeadamente, da disseminação do conhecimento especializado, da automatização de processos, da formação técnica de novas equipas especializadas, entre outros. Este trabalho tem como principal objectivo apresentar uma proposta inovadora de modernização das actividades subjacente ao controlo de segurança de grandes barragens de betão com base em processos automatizados e com características inteligentes. Neste contexto, o Laboratório Nacional de Engenharia Civil (LNEC) promoveu, no início de 2004, o desenvolvimento do sistema GESTBARRAGENS, tendo como parceiros o Instituto de Engenharia de Sistemas e Computadores: Investigação e Desenvolvimento (INESC-ID) e a Companhia Portuguesa de Produção de Electricidade (CPPE/EDP).

Data quality tools aim at detecting and correcting data problems that affect the accuracy and efficiency of data analysis applications. We propose a classification of the most relevant commercial and research data quality tools that can be used as a framework for comparing tools and understand their funcionalities.

Some artificial accelerated methods are currently used and accepted in the prediction of polymer lifetimes. However, in order to evaluate the durability of these materials, it is indispensable to reproduce the natural weathering phenomena as closely as possible. To attain this target, it is fundamental to understand the role of the atmospheric agents in the photo-degradation. The importance of radiation and temperature in the degradation of polymers is universally recognised. However, there is a trend to underestimate other environmental agents, such as humidity and rain, which play an important part in the evolution of degradation in certain compounded polymers. The objective of this paper is to show the fundamental role of water in the mechanism of degradation of TiO2 pigmented PVC formulations, and compare the results from different exposure methods, considering the influence of this degradation agent.

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The state of the art in predicting weatherability lags far behind the need for such predictions. The exact prediction of the useful lifetime of a given polymer in a specific geographic location is still the dream of both specifiers and manufacturers. As a result, the estimation of durability of these materials remains one of the most challenging issues in weathering studies.

The generation of tidal asymmetries in estuaries is analyzed by examining the differences in celerity at high and low tide. An analytical expression for the difference between ebb and flood durations is introduced and applied to a cross-section composed by a channel flanked by tidal flats. The expression depends on the cross-sectional average of the celerity, for which two approximations are proposed and verified with a numerical model. Results confirm that tidal flats enhance ebb dominance, while large tidal amplitudes promote flood dominance. Maximum ebb dominance occurs for tidal flats at, or above, mean water level, depending on tidal amplitude and the extent of the tidal flats. Finally, qualitative arguments indicate that friction also enhances flood dominance.

Dans le sud de la France, à proximité de la ville de Millau, le raccordement de Clermont-Ferrand à Montpellier par l’autoroute A75 a nécessité la construction d’un ouvrage exceptionnel pour franchir la vallée du Tarn. L’ouvrage est constitué d’un tablier en caisson entièrement avec un platelage orthotrope, le tout entièrement en acier. Il est soutenu par des haubans à des pylônes également en acier. Le montage a été réalisé par lançage sur des palées métalliques provisoires. Ce pont, long de 2460 mètres, est actuellement le viaduc le plus haut du monde. Il possède en effet des piles en béton atteignant 245 mètres de hauteur et son plus haut pylône représente une hauteur totale de 346 mètres au dessus du Tarn. Cet article montre comment a été élaboré le projet de l’un des plus grands ouvrages haubanés à travées multiples de ce début du vingt-et-unième siècle construit dans un site particulièrement difficile.