Artigos de Revista

This paper analyses the possibility of using air curtains to prevent smoke flow from fire compartments. Full size experiments have been carried out and several relevant conditions to assess smoke-tightness have been tested. The smoke temperature during the tests was ranging from 182ºC to 351ºC, the angle measured between the curtain axis and the vertical plane was ranging from 18º and 26º, the nozzle thickness was ranging from 0.017 m to 0.045 m and the velocity at the nozzle was ranging from 8.3 m/s to 19.9 m/s. During the tests, the air curtain’s nozzle was positioned horizontally at the top of a permanent opening (door). With this configuration, we obtained an approximately vertical downward jet through the used opening. This paper includes the final results of the tests and develops an analytical tool for predicting the performance of air curtains. It was concluded that it is possible to achieve smoke-tightness, provided that the adequate plane jet parameters and the compartment’s smoke exhaust are correctly adjusted. According to this analysis, the smoke-tightness limit corresponds to equation B=??P?_a???P?_s =-0.30 u_a?u_(a_min) +1.25 (with 1.30? u_a?u_(a_min) ?1.67).

This paper describes the preliminary developments of an innovative integrated tool for the numerical modelling of oscillating water column (OWC) wave energy converters (WEC) integrated in vertical breakwaters. The main purpose of the tool is the numerical modelling of wave propagation from offshore to nearshore, wave-structure interaction, and the complex nonlinear hydrodynamic and aerodynamic phenomena that occur in OWC-WECs. The tool development and validation were supported by experimental data from physical model tests carried out in a wave flume at the Portuguese National Laboratory for Civil Engineering (LNEC). Prototype data were also available for the Pico OWC-WEC in the Azores, Portugal, monitored by the Portuguese Wave Energy Centre since 2005. Application of the tool for sea-wave characterization at the Azores archipelago and calculation of the corresponding wave power for a period of 10 years at various points around each island show that, in winter, there is good availability of wave energy in most quadrants of each island. In summer, the resource exploitation is only worthwhile on the north-west coasts of the islands. Physical and numerical modelling results for an OWC with a fully open chamber show good agreement between experimental data and numerical values for several incident wave conditions. The analysed results include the time series of the free-surface elevation at different locations, the time series of the mean free surface inside the water chamber, the amplification factors, the phase angles and the velocity vectors at the highest and the lowest positions of the mean free surface inside the chamber. The tool showed its potential to be useful in supporting ocean and coastal engineering projects due to its capacity to effectively reproduce the main phenomena involved in these types of studies.

Apresenta-se neste artigo um estudo de análise da segurança das pontes Criz II e de São João de Areias, na albufeira da barragem da Aguieira, em Portugal, durante a execução de novas fundações, no âmbito das empreitadas de reabilitação, na proximidade dos pilares afetados por reações expansivas do betão no seu embasamento. A ação dinâmica induzida pela perfuração de maciços rochosos foi modelada como uma ação periódica composta por um momento torsor aplicado na fundação de cada pilar isolado combinado com três forças ortogonais representando a força imposta pela caroteadora e os desequilíbrios das tensões de corte por rotação. Através da análise dinâmica linear das estruturas completas e de análises não lineares estáticas e dinâmicas dos pilares, foram estabelecidas as condicionantes às vibrações induzidas pelas máquinas caroteadoras, nomeadamente em termos de limites máximos da resposta em velocidade no topo dos embasamentos, e definidas as condições de monitorização da estrutura durante a obra. Estas especificações foram elaboradas em estreita colaboração com técnicos da Infraestruturas de Portugal, I.P., e incluídas nas Cláusulas Técnicas Especiais para o lançamento da empreitada.

The ability to adequately prioritise maintenance of sewer systems significantly increases the quality of the service provided by these systems. It is thus important to optimise decision making processes, a more feasible challenge as digital data becomes available. When defining the variables that should be used to predict sewer failure, it is important to identify the ones that mostly influence the quality of the predictions (i.e. the response variable) or to define the smallest number of variables that is adequate to conduct accurate predictions. In this study three different methods to identify the most important variables are evaluated. The first is the mutual information indicator, the second method is the stepwise search approach and the third method uses the out-of-bag samples concept, based on the random forest algorithm. The methods were applied to a real data set that consists on the categorization of sewer condition (critical, non-critical) and their physical characteristics (e.g. Length, Age, Diameter, Slope and Material). The mutual information and the stepwise search methods provided good predictions and produced similar results. The results obtained using out-of-bag samples based on random forest were somewhat different and can be justified by the lack of robustness to imbalanced class distributions.

This paper aims to spatially characterize the marine intrusion in the case of the Bouteldja main aquifer using the GALDIT method coupled with a geostatistical approach. The latter was used to compensate the weakness of GALDIT method for not considering the spatial variability of the studied variables. Using a field data set of the Bouteldja aquifer, the semi-variograms of four continuous important variables (hydraulic conductivity A, groundwater level L, thickness T and sea water intrusion I) were studied and modeled. The obtained structures were mainly composed of spherical models with a small nugget effect, except the I variable which has shown a perfectly continuous Gaussian model with zero nugget effect, arguing that the marine intrusion is seriously present and continuous. These individual results were also mapped by kriging and the intrusion easily shown on the field. However, the GALDIT computation and mapping did not confirm the found intrusion. It has merely shown a medium to low vulnerability in narrow and parallel bands close to the shore area. This work has shown that the GALDIT method used solely, without a geostatistical approach, would lead to a misinterpretation of the vulnerability of a main aquifer to saline intrusion. Keywords · Shore aquifer · Bouteldja · Vulnerability · · Pollution · Salinity

Understanding the out?of?plane response of masonry infill walls and preventing their progressive collapse mechanisms is very important for earthquake?prone countries to prevent loss of life and economic loss. In fact, having a realistic collapse mechanism assessment allows suitable prevention measures to be adopted. With this purpose in mind, two full?scale one?bay one?story substructures of reinforced concrete frames (RCF) with infill walls were tested on a shake table. These 2 specimens were designed to represent the response of a typical RC Frame at the fifth floor of an 8?story building, namely the out?of?plane failure of its infill wall under combined bidirectional seismic load. Both specimens were composed of a singleleaf clay brick infill wall surrounded by the RC Frame. However, while the first specimen corresponds to an unreinforced masonry configuration, the second specimen includes horizontal bed joint reinforcement as a strengthening/retrofitting technique. The main novelty of this study is the application of a bidirectional and simultaneous dynamic loading to the specimen, such that in?plane and out?of?plane effects are evaluated together. This work presents several interesting experimental results, with particular emphasis on the bearing capacity of the specimens against out?of?plane failure. As expected, the in?plane capacity of the reinforced infill specimen is larger than that of the unreinforced infill specimen. Nevertheless, the out?of?plane bearing capacities of the two specimens are very similar, in contrast to their ductility capacity, which is significantly increased in the reinforced masonry specimen. The capacities of the two specimens for both in?plane and out?of?plane directions, as predicted by formulations in the literature, are given. The differences found between these calculations and the results of the tests are discussed, andmay possibly be explained by the parameters considered in the different formulations.

Joint statistical models for long-term wave climate are a key aspect of offshore wind engineering design. However, to find a joint model for sea-state characteristics is often difficult due to the complex nature of the wave climate and the physical constraints of seastates phenomena. The available records of wave heights and periods are often very asymmetric in their nature. This article presents a copula-based approach to obtain the joint cumulative distribution function of the significant wave heights and the up-crossing mean period. This study is based on 124-month hindcast data concerning Horns Rev 3 offshore wind farm. The extra-parametrization technique of symmetric copulas is implemented to account for the asymmetry present in the data. The analysis of the total sea, the wind-sea and primary swell components is performed separately. The results show that the extra-parametrization technique with pairwise copulas consistently provided a better goodness-of-fit when compared to symmetric copulas. Moreover, it is demonstrated that the separation of the total sea into its components does not always improve the extra-parametrized copula’s performance. Furthermore, this article also discusses copulas application to offshore wind engineering.

Neste artigo abordam-se, especificamente, as bay-windows e o que se designa de outros "lugares-janela", ou "sítios junto à janela", por se considerar que, em termos de uma satisfação global e caracterizada dos habitantes, tais elementos podem assumir uma expressiva importância, associada a interessantes aspectos de apropriação e de satisfação no interior das nossas casas, até porque proporcionando o estar quase “lá fora”, mas bem abrigados e rodeados pelos nossos mundos domésticos.

A nossa habitação pode e deve ser e ir evoluindo, gradualmente, no sentido de ser verdadeiramente a nossa “casa”, base amigável e estimulante dos nossos mundos pessoais, e assim, suporte directo da nossa identidade familiar e individual, uma verdadeira “casca de caracol”, bem à nossa medida, física, psicológica e afectivamente. Neste sentido, no artigo aborda-se este tema, globalmente, e em seguida apontam-se associações e hábitos interessantes sobre recantos domésticos, assim como alguns dos mais significativos aspectos ligados a estes recantos, em termos de motivação para o seu uso, problemas mais correntes e outras questões que aí, frequentemente, se colocam (dimensionais e outras).