Papers

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Soil-rockfill mixtures (SRMs) are economical and environmentally friendly materials. Due to the absence in theliterature of constitutive models specifically developed and tested for SRMs, a new constitutive model, theSubloading Surface Rockfill Model, is presented. This model allows the occurrence of plastic strains inside the yield surface, inducing a smooth elastic/plastic transition. The results of experimental tests for different coarse fractions (CF) of several SRMs performed on samples from Odelouca Dam are compared with those obtained with this model. The model was able to reproduce reasonably well the response of SRMs considering the intrinsic variability of the tested specimens.

Over the last 50 years, a significant amount of effort has been taken to develop numerical approaches andtools for the structural analysis of masonry. These range from considering masonry as an anisotropic continuum(macro-models) to the more detailed ones considering masonry as an assemblage of units andjoints (micro-models). In this paper, a detailed micro-modelling approach for the analysis of masonrycouplets and prisms is proposed. The approach represents masonry units and mortar joints as an assemblageof densely packed discrete irregular deformable particles bonded together by zero thickness interfacelaws. The mechanical properties (here referred to as micro-properties) of irregular particles andcontacts are responsible for the mechanical behaviour of masonry. In addition, the approach allows failureto occur either at the brick, mortar and/or brick/mortar interface. A series of computational modelswere developed and their results are compared against small-scale experimental findings. A good agreementbetween the experimental and the numerical results was obtained which demonstrates the hugepotential of the modelling approach proposed. The significant advantage of this approach is to modelcracking as a real discontinuity among particles and not as a modification in the material properties.In addition, reliable prediction of masonry strength can allow one to reduce the costly and timely experimentaltesting and avoid the reliance on conservative empirical formulas.

Está em curso um projeto de geminação a cargo de um consórcio franco-português, ao abrigo do Acordo de Associação Argélia-UE, que tem por objetivo prestar apoio ao "Organisme National de Contrôle Technique des Travaux Publics" (CTTP) argelino na implementação de um sistema de suporte à decisão para a gestão da rede de estradas e das obras de arte rodoviárias. Neste artigo pretende-se dar a conhecer sumariamente os principais aspetos desta interessante cooperação científica e técnica internacional, em que Portugal é representado pelo Laboratório Nacional de Engenharia Civil (LNEC).

This paper describes a methodology to determine the optimal size of a Wells turbine to be used in an OWC device taking into account hydro-aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The proposed model, named turbine diameter optimization (TDO) model, considers the movement of the water surface inside the OWC chamber as a piston movement in response to the hydrodynamic forces from the incoming waves. The aerodynamic is based on the first law of thermodynamics applied to the air column of the chamber. The power-pressure curve of the turbine and the air pressure control by relief valve are implemented in the model to determine the turbine power output for several regular incident waves. The TDO model is initially calibrated by a numerical model based on Reynolds-Average-Navier-Stokes (RANS) equations for each wave component of an expected sea state distribution. Thereafter, the power output generated by turbines of several sizes is calculated with lower computational cost (few minutes) in comparison with RANS based models (thousands of hours) in a personal computer. This developed methodology is an important support to the process of turbine sizing for an OWC device for an expected sea state distribution.

Managed aquifer recharge (MAR) can be affected by many risks. Those risks are related to different technical and non-technical aspects of recharge, like water availability, water quality, legislation, social issues, etc. Many other works have acknowledged risks of this nature theoretically; however, their quanti

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, edefinidas 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.