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Remote access to data and experiments. application to hydraulic laboratory facilities
No full textRADE, acronym for Remote Access to Data and Experiments, is a Joint Research Activity of project HYDRALABIV - More than Water. Its aim is to develop a robust set of information systems to improve access to hydraulic experiments and data through innovative use of modern data management, curation and communication technologies. The objective of the present work is to describe two different methodologies, developed by the National Laboratory for Civil Engineering (LNEC) and by DELTARES, on remote access to data and experiments applied to hydraulic laboratory facilities.359-367ppCoastlab 2014 - 5th International Conference on The Application of Physical Modelling to Port and Coastal ProtectionDHA/NP
Embedding and withdrawal resistance of screws on thermal treated wood
No full textTests were conducted at LNEC to assess withdrawal resistance and embedding strength
of commercial heat treated wood (ThermoWood®) Thermo-D pine with various types of screws, to predict the short-term performance of screwed joints. These had in mind a suitable design and detailing of screwed joints in ThermoWood®, even in non-structural applications, where the wood components have to fulfil certain strength requirements and their assembly and fixings have to be strong enough to assure long-term
performance and durability. Test results were analysed as a function of the material
density, and compared to non-modified wood, in the light of common joint design
principles. This work contributes to debate the suitability of using the equations given
by Eurocode 5 (EN 1995-1-1:2004/A1, 2008) to the design of screwed joints in nonstructural
ThermoWood®.The authors thank Jular Madeira for providing ThermoWood®, and SFSintec for the connectors and application devices used in this study and LNEC for the facilities.44DE/NCE201410-12 de març
Tomografias Pseudo-3D de resistividade elétrica
No full textA produção de cartas de resistividade elétrica (informação 2D horizontal) a diferentes níveis de profundidade envolve muito tempo. Os estudos a 3D envolvendo este método de prospeção geofísica são igualmente muito demorados e exigem grande volume de equipamento. Para procurar contornar estas dificuldades desenvolveu-se uma aplicação informática que, com recurso a perfis de resistividade elétrica (informação 2D vertical) dispostos numa malha, produz secções 2D (horizontais) a diferentes profundidades, permitindo assim ter um conhecimento pseudo-3D do local em estudo. A sua aplicabilidade foi testada com dados colhidos no campus do Laboratório Nacional de Engenharia Civil (LNEC) e num outro local, este no âmbito de um projeto de investigação para o qual foi necessário caracterizar um campus de investigação com recurso a diversos métodos geofísicos.6pDG/NGE
Orthodynamometer for Measurement of Longitudinal and Transverse Loads in Wind Tunnel Testing
No full text7ppEURODYN - 2014 - IX International Conference opn Structural DynamicsCIC/NSE
Monopolos auto-suportados para telecomunicações. A influência da localização e da geometria da estrutura na definição da ação do vento
No full textNeste trabalho apresentam-se os resultados obtidos de um estudo paramétrico realizado com o intuito de quantificar a influência relativa da localização e características geométricas da estrutura em monopolos auto-suportados utilizados para telecomunicações, e aquando da definição da ação do vento. Pretendeu-se ainda conhecer a importância global destes parâmetros aquando da análise e dimensionamento deste tipo de estruturas.15pDE/NC
Medição não-intrusiva da densidade superficial de depósitos de sedimentos em camada fina
No full textO processo de medição de espessuras e de densidades superficiais de sedimentos depositados em modelos
físicos tem sido motivo de investigação, conhecendo-se alguns métodos para o efeito, mas todos eles exibindo limitações sérias, em especial quando se pretendem medir depósitos em camada fina, isto é, com poucos milímetros de espessura. O presente estudo refere-se a um método para realizar este tipo de medição, baseado na variação de resistência elétrica entre elétrodos que fiquem cobertos com a camada de sedimentos. Pretende-se aplicar um método de medição que não perturbe o processo de sedimentação, com sensibilidade para medição de camadas finas (até 1cm) de sedimento, que permita a medição ao longo do tempo, robusto aos efeitos eletroquímicos da água e robusto às perturbações do meio (variação de temperatura, salinidade e nível da água). Inicialmente é feito um resumo sucinto do estado de arte dos métodos de medição de sedimentos, com a descrição das vantagens e limitações de cada um e salientando a sua aplicabilidade à medição de sedimentos em camadas finas. Segue-se uma descrição do princípio de medição adoptado, identificam-se diversos fatores de influência que, na abordagem convencional, perturbam ou dificultam a medição pretendida, propondo-se soluções para os compensar ou os retirar da cadeia de transdução. É feita uma descrição do circuito eletrónico desenvolvido que permite implementar o método de medição proposto. Finalmente são apresentados os resultados de um estudo experimental feito em protótipo que mostram a viabilidade do método com as inovações introduzidas para superar as limitações do princípio de medição.27-42ppN.º 7CIC/NSEMRevista Medições e Ensaio
Modeling the beginning of expansion acceleration due to alkali silica reaction in concrete. Part 2- Comparison of model estimates with experimental data
No full textThis paper compares expansion model estimates and experimental data. In an earlier paper, a diffusion controlled topochemical model fitted to isothermal curves yielded kinetic parameters (induction time and kinetic constant). Linear regression of their Arrhenius plots modelled the constants dependence on temperature, allowing to predict induction times at given temperatures and times in laboratory. Comparing expansions thus estimated with experimental values at 37 ºC in mortar-bars immersed in 1M NaOH solution ASTM C 1260 adapted test, the expansion start matched the modelled induction time. The experimental and modeled expansion after that time follow different patterns. The model may use known correlations for correcting for different alkalinities and humidity’s,.
The model possibilities were checked with published data on ASR-affected concrete . The estimates matched real values despite high errors in statistical processing and environment data. Improvements are proposed for reducing errors, in modeling major factors , and application to other cases.5pThe authors thank the financial support provided by Fundação para a Ciência e Tecnologia (FCT), through the project EXREACT (PTDC/CTM/65243/2006).DM/NM
First Infilling of the Venda Nova II Unlined High-Pressure Tunnel: Observed Behaviour and Numerical Modelling
No full textThe underground structures of the Venda Nova
II reversible hydroelectric power scheme present features that make it an interesting case study. Worthy of mention are the inclination and length of the unlined pressure tunnel, the high water head and the great depth of the powerhouse cavern. In projects of this type, the main effect of
the internal water pressure in the pressure tunnel is the establishment of seepage from the tunnel into the rock mass, which can reach the adits and the powerhouse cavern.
This seepage is influenced by several factors, such as the geometry of the underground openings, the rock mass
properties—namely, the joints characteristics—and the stress state resulting from the excavation and from the internal water pressure. This article presents the main
features of the underground structures of the Venda Nova II scheme and a detailed description of the observed behaviour during the first infilling of the pressure tunnel. A
three-dimensional multi-laminated numerical model of the rock mass hydromechanical behaviour was developed to help understand the observed behaviour. The model assumptions in regard to the geometry of the openings, the jointing pattern, the rock mass hydraulic and mechanical behaviour, as well as the hydromechanical interaction, are described. Results obtained with the numerical model are
presented and compared with the observed behaviour. Finally, the validity and importance of the numerical tools for the interpretation of the rock mass hydromechanical behaviour is discussed.233885–904Volume 47, Number 3DBB/NMMRRock Mechanics and Rock Engineering, Special Issue: Water Issues in Underground Excavation
Water and nitrogen budgets under different production systems in Lisbon urban farming
No full textPublic concern is growing over soil and groundwater contamination from the use of agrochemicals
in urban farming. Heavily used nitrogen (N) fertilisers are converted to nitrates
that can be a health hazard. In this study, water and N budgets over a 1-year period are
presented for typical urban vegetable gardens in Lisbon. A conceptual analysis supported
by an integrated methodology of field experiments and modelling identified the N surpluses
associated with conventional and organic gardens. It is concluded that the
gardening systems are continuously cropped using high N and water application rates. For
all of the case-study allotments, the N inputs, mainly from organic amendments with
diverse N release rates, were higher than the crop uptake generating surpluses that were
lost by different processes. On one study site a drainage flux of 280mmyr 1 was calculated,
with a mean concentration of 295 mg NO3
l 1. On another site N accumulated in the lower
soil depths at a rate of 420 kg NO3
ha 1 yr 1. The cumulative impact of N surpluses on the
environment and human health must be considered. To minimise adverse impacts, we
propose the selection of organic fertilisers with N release rates close to the crop N uptake,
the prevention of excess irrigation to minimise N leaching and gaseous losses and the
inclusion of the non-fertiliser N sources in the fertiliser calculations. It is shown how an
integrated model can be used to predict the N release dynamics from the organic fertilisers
as affected by the moisture conditions.65-79125DHA/NREBiosystems engineerin
Experimental study of stability of submarine outfalls in muddy soils
No full textMarine structures built on muddy soils, such as breakwaters and submarine outfalls, are subject to settlement, scour and liquefaction and the mechanics of these processes are still uncertain. The aim of the present experimental study is to investigate stability of submarine outfalls in low quality soil. Physical modeling, carried out in the wave flume at UNAM, Mexico, is described and the results are presented and discussed. Tests were performed for different wave conditions (wave heights and periods), different soil characteristics (several mixtures of kaolinite and sand) and three structural layouts: the pipe resting on the soil, the pipe partially buried and a totally buried pipe.
The pore pressure for different positions on the soil and the movements of the pipes were measured, together with surface elevation along the flume.16pDHA/NP