Artigos de Revista

The village of Agualva, located in Terceira Island, Azores, Portugal, experienced severe flooding on the early morning of 15th of December 2010. The flooding was caused by a short-duration and extreme intensity rainfall event. In less than four hours a total of 70mm of rain rushed down the catchment, flooding several streets and causing the main water course to transport a mix of mud, rocks and debris.

Although rising global sea levels will affect the estuarine flooded areas over the coming decades, the local and regional-scale processes will also induce important changes in these coastal systems. The main aim of this work is to investigate possible tidal changes in estuarine systems induced by local geomorphologic modifications, analyzing the particular case of Ria de Aveiro which is in risk of inundation. Located in the Portuguese west coast, this tidally driven lagoon has a large area of mostly abandoned salt pans, which are in progressive degradation caused by the lack of maintenance and by the strong currents which erode their protective walls. To explore possible tidal changes the hydrodynamic model ELCIRC was applied to Ria de Aveiro to simulate and analyse the impact in the lagoon hydrodynamics of this degradation which results in the enlargement of the lagoon flooded area. A high-resolution grid (grid spacing of the order of 1 m) was developed in order to represent the narrow channels adjacent to the salt pans. The hydrodynamic model was then successfully calibrated and assessed for skill for the Aveiro lagoon through comparison between measurements and model results and quantification of the numerical accuracy. The model was subsequently used to investigate the effect of the flooded lagoon area enlargement on tidal propagation in Ria de Aveiro. Simulations were performed for three geomorphologic configurations, representing the reference or present situation and two flooded scenarios. Results were compared through the analysis of tidal currents, tidal asymmetry and tidal prism. The increase of the lagoon flooded area results in an intensification of the tidal currents, tidal prism and tidal asymmetry. Results also indicate that the tidal prism further increases when the flooding depth increases. Otherwise, changes in tidal currents and in tidal asymmetry pattern are negligible with the increase of the flooded area depth. These results indicate that modifications of the flooded area of estuarine systems will result in tidal changes, with an intensification of the actual tidal patterns induced by the enlargement of inundation areas.

This article presents a study on the time-dependent behaviour of timber lightweight concrete composite floors. The option of using lightweight aggregates in concrete (LWAC), instead of normal weight aggregates, is the focus of this document. The load-slip behaviour of SFS-screwed joints in timber-LWAC structures is analysed both for the short term and the long term cases. The study takes advantage of an experimental programme carried out at the University of Coimbra where several timber-LWAC specimens were tested for 600 days. The load-slip behaviour of the connections is very important for the behaviour of the whole structure. The last aspect that is developed in this article concerns the time-dependent behaviour of LWAC composite floors. The calculated results obtained through the computer programme proHBV, developed at the University of Stuttgart, proved to be very close to those obtained from tests carried out at the University of Coimbra. As explained in this article, the direct application of the design rules for creep in concrete and timber, as presented in Eurocodes 2 and 5, results in great deviations from the actual behaviour of structures composed of two materials, timber and concrete. To overcome this difficulty, the authors also present a simplified procedure that can be taken as an extension of the Eurocode design philosophy. This simplified procedure does not need the use of computer programme proHBV, and is much more accurate than the current Eurocode proposals. The deviation of the simple design procedure from the test (even if a bit higher than that of proHBV) is in the order of usually accepted values for practical design, however, the advantage of this approach for the practice is decisive.

O método dos elementos discretos adoptando partículas para discretização do domínio tem sido utilizado no estudo do fenómeno da fractura em meios não homogéneos, como o betão e a rocha. Neste artigo, é proposto um modelo de análise para o betão armado no qual as armaduras são modeladas com elementos rígidos unidimensionais ligados por molas. Os elementos rígidos interagem com o betão, modelado por partículas circulares, através de uma interface de contacto. O modelo é validado com base em ensaios de flexão em viga a três pontos e a quatro pontos, sem armaduras de esforço transverso. No ensaio de flexão a 3 pontos o modelo dá uma boa aproximação do comportamento real em termos do processo de evolução da fractura e da relação carga-deslocamento. No ensaio de flexão a 4 pontos, verifica-se uma boa correlação com os resultados experimentais, nomeadamente o valor da carga última, o efeito de escala e a evolução do processo de fractura.

Apresentam-se, neste artigo, os conceitos da inferência paramétrica Bayesiana, no contexto da estimação dos parâmetros de amostras aleatórias normais. São abordados temas práticos não triviais, tais como as distribuições anteriores informativas e a sua eliciação paramétrica pelo método empírico. A finalizar o artigo, é apresentado um exemplo de aplicação da metodologia Bayesiana a um problema de estimação paramétrica no âmbito da engenharia de estruturas.

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Available data relating to major pluvial flooding events in Jakarta, Indonesia were used to investigate the suitability of two different levels of sophistication in urban modelling tools for modelling these events. InfoWorks CS v9.0 was employed to build 1D and 1D/2D models of a 541 ha area of inner city Ciliwung River catchment which has a history of being particularly badly affected by flooding during heavy rainfall events. The study demonstrated that a 1D model was sufficient to simulate the flood extent of a major event using the limited data available. While the 1D/2D model also performed well, more data and time would have been required to match the 1D model’s simulation of flood extent. Much more detailed data would have been required to produce reliable results in the 1D/2D model and to enable any kind of verification or calibration of the two models beyond visual comparison with crude flood extent maps.

Em áreas urbanas a exiguidade de afloramentos, que representa uma dificuldade na aplicação das metodologias habitualmente utilizadas no reconhecimento geológico, é compensada pela existência de grande volume de dados resultantes de trabalhos de prospecção. Os dados de estudos geológicos e geotécnicos realizados em Lisboa constituem, assim, um importante conjunto de informação, muito diversa, dispersa por muitas instituições e, em grande parte, disponível apenas em formato analógico. No âmbito do Projecto GeoSIS_Lx pretende-se desenvolver uma Base de Dados geotécnicos, integrando a informação num Sistema de Informação Geocientífico. O objectivo principal é gerar um modelo geológico 3D que, interagindo com a Base de Dados, permitirá a constante actualização e validação cruzada do modelo e dos dados. Neste trabalho é apresentada a estrutura e o conteúdo da Base de Dados.

Este artigo ilustra o trabalho que o Núcleo de Portos e Estruturas Marítimas do LNEC tem vindo a desenvolver no âmbito da verificação da segurança à estabilidade e ao galgamento de estruturas marítimas utilizando métodos probabilísticos de níveis II e III. Apresentam-se dois casos de estudo: 1) verificação da segurança ao modo de falha por galgamento de uma estrutura de protecção costeira; e 2) verificação da segurança ao modo de falha por instabilidade hidráulica do manto protector de um quebra-mar de taludes