Artigos de Revista

Os modelos de partículas, ao terem em conta a estrutura granular da rocha, consideram de forma explícita a variabilidade associada ao material, razão pela qual têm sido aplicados com sucesso no estudo da fratura em rocha. Neste trabalho é apresentado um modelo de partículas 3D com base nos diagramas de Laguerre-Voronoi da estrutura granular, que permite ter em conta de forma aproximada uma geometria do tipo poliédrica mantendo a simplicidade e o reduzido esforço computacional característico dos modelos de partículas esféricas. Propõe-se então um modelo de contacto múltiplo no qual a superfície de contacto é definida com base nas facetas dos diagramas de Voronoi. O modelo de partículas é validado com base em ensaios experimentais em rocha (triaxiais, uniaxiais e ensaio Brasileiro). Apresentam se vários estudos paramétricos que evidenciam a influência dos parâmetros do modelo de partículas nas propriedades macroscópicas elásticas e resistentes obtidas numericamente. É ainda analisada a relevância de um modelo de contacto com leis de enfraquecimento bilinear em tração e corte que conduz a valores coerentes de tração última em ensaios de tração diretos e em ensaios Brasileiros.

Numerical simulations using the SWAN-VEG model (Simulating WAves Nearshore, with vegetation module) were performed considering the case of Ilha Solteira (SP) reservoir, a navigable stretch of the Tietê

Transition zones to bridges and other structures are critical locations in railway tracks that frequently evidencepoor long-term performance. Under sleeper pads (USPs) are reported to reduce ballast degradation and controlthe vertical stiffness of the track, which suggests that USPs can contribute to mitigating the frequent negativeeffects associated with transitions zones. Aiming at understanding in greater depth the influence of USPs on thedynamic behaviour of transition zones and at improving the design of such railway structures, the authors havedeveloped an extensive experimental and numerical study. 3-D FEM models using state-of-the-art numericalapproaches were successfully calibrated and validated using experimental measurements. Simulations supportedprevious findings, highlighting the potential benefit of USPs and pointing to the need to careful designing of theresilient properties of USPs and their arrangement along transition zones, so as to avoid introducing abruptvariations in track vertical stiffness.

O que se aponta no artigo relativamente ao pormenor/detalhe doméstico refere-se, essencialmente, a matérias suplementares, ou melhor dito, paralelas, às directamente associadas aos espaços da habitação, e que são, portanto, globalmente bem distintas dos amplamente conhecidos aspectos funcionais domésticos. Aborda-se, então, globalmente, a temática do

Desenvolve-se um primeiro artigo sobre a temática intitulada

This work presents results of concrete carbonation after 10 years of exposure to a natural environment not sheltered from rain, and the values are utilized for the application of the k-value concept used within EN 206 for Type II additions to concrete. The concrete mixtures were prepared with Portland cement and different replacement levels of cement by fly ash (FA), ground granulated blast furnace slag (GGBFS), or both FA and GGBFS and using distinct water/binder ratios. The concrete performance is related with the binder constituents and dosages through the k-value concept. Thirty-three concrete mixtures were tested and the results show a consistent decrease of carbonation resistance when the water/clinker ratio increases, which is in accordance with the low k-values obtained for fly ash and slag. The analysis performed also shows that the mixtures with FA present lower carbonation resistance than those with GGBFS, for the same cement replacement level.

Ballast aggregate is a natural material widely used in railway lines. Its mechanical properties and particle geometry are meticulously defined using well-established standards and characterisation procedures. Though extensively validated, these procedures have some limitations: they are operator dependent; only provide major particle dimensions; do not inform on surface colour; nor allow for advanced particle wear analysis or particle-based simulations. This work presents a cost-efficient photogrammetry method for 3D reconstruction of ballast particles, as an alternative to the significantly expensive laser scanning. It produces digital models of equivalent or higher quality, allowing for advanced and automated particle geometry analyses. Particle meshes produced here are shared among researchers.

Apresenta-se uma plataforma WebSIG para suporte à gestão do risco de inundação, aplicável do rio atéao oceano, incluindo a dimensão urbana. Permitindo o acesso diferenciado e produtos customizados para váriosutilizadores, esta plataforma oferece um acesso central a toda a informação útil para a gestão da inundação, querpara o planeamento, quer para situações de emergência. Baseia-se no acoplamento de vários modelos que simulamtodos os processos geradores de inundação: marés, sobrelevação de origem meteorológica, agitação marítima,escoamento fluvial, drenagem urbana e eventos de precipitação. Quando a interação entre processos é fundamental,o acoplamento é efetuado através da modelação integrada dos mesmos (para ter em conta p.ex. a interação entre aagitação marítima e as correntes). Este sistema de modelação está integrado na plataforma de previsão em temporeal do LNEC (WIFF - Water Information Forecast Framework) que produz diária e automaticamente previsões a 48 horasda inundação no caso de estudo escolhido. Estas previsões são depois disponibilizadas numa plataforma WebSIG,através de um conjunto de produtos customizados às necessidades do utilizador, como boletins de alerta, mapasde previsão da circulação e de inundação e séries temporais de grandezas em pontos pré-selecionados (sensoresvirtuais). Oferece ainda serviços de comparação automática com dados em tempo real e sistemas de alerta. Ilustra-sea valia desta plataforma numa aplicação à gestão da inundação no estuário do Tejo, com destaque para os alertascustomizados ao interesse da Proteção Civil, desde a escala oceânica até à região estuarina de interesse

Stepping away from traditional crash-based road safety measurements, several safety performance indicators (SPI) have been proposed in the past few years. SPI can incorporate quantitative and qualitative information on specific aspects that are known to have influence in the safety levels and, not only measure the influence of various safety interventions but also enable comparisons between different road systems. This paper presents the results of the application of a road network SPI to the entire Portuguese road network. This SPI aims at evaluating at the network level, if the connections between urban centres within a region are made by the adequate type of roads regarding generic safety criteria. To this end, the connections to be assessed were classified into pre-defined theoretical safety classes, based on the population of the connected urban centres. Then, the observed safety class of these connections was assessed according to the characteristics of their cross-section and associated road environment of the existing connection between the two urban centres. If the observed class is ensured by a road of higher or equal class than the pre-defined theoretical level in all its extension, the link is considered to be of the appropriate class. For each connection, the results of its evaluation are expressed as a binary value: 0 when the class is not appropriate; and 1 when it is appropriate. The evaluation results are weighted by the road length and aggregated by connection class and throughout the whole road network. The results show a satisfactory network configuration with an SPI of 94% connections with class equal to or higher than the adequate for the type of connection between urban centres they established. The above insights can help in the identification of potential operational inconsistencies that may require safety-related interventions and used for international benchmarks against existing SPI evaluations.

Scour protection is an important component of fixed bottom foundations for offshore wind turbines. Depending on the hydrodynamic conditions, they might be indispensable to avoid the structural collapse of the foundation due to scour phenomena. The design of scour protections is typically deterministic, which often results in overestimated mean diameters of the armour layer.Moreover, the design methodologies currently applied do not provide a measure of safety associated with the proposed design. The present research proposes a novel methodology to assess the safety of the protection and to perform the probabilistic design of static and dynamic scour protections. A case study based on Horns Rev. 3 offshore wind farm is used to show how to select the mean stone diameter according to a pre-defined probability of failure of the protection. The results show that a dynamic scour protection could be safely designed with a reduction of the mean stone diameter up to 15 cm, when compared with the statically stable protection.