Papers
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The "New Lisbon Airport" project and the Location Assessment Study carried out by LNEC
A brief presentation is made on the background and state of progress of the Project of the
Year: 2009
Number Pages:
9-12 pp.
Author(s): Macedo, A. L.
Editor: AT Osborne B. V.
Volume:
NETLIPSE Magazine # 6.
Keywords: Location assessment; Airport infrastructures
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The Application of Fluorescence Microscopy and Scanning Electron Microscopy in the Detection of Delayed Ettringite Formation in Concrete
The degradation of concrete structures caused by delayed ettringite formation (DEF) is a problem that nowadays affects many concrete structures worldwide. This pathology is due to the formation of an expansive compound ettringite - inside the material. This is a hydrated calcium sulphoaluminate produced by the chemical reaction between sulphate ions, calcium hydroxide and alumina present in the Portland cement paste. This product, normally formed during the hydration of cement, presents an acicular morphology (needles) that can be observed by scanning electron microscopy (SEM). However, DEF can also be formed after the setting of the cement causing, in this case, a deleterious expansion of the concrete. This secondary ettringite can also be produced after an excessive heating of the concrete, caused by a high amount of cement or by the use of heat cure. SEM has been used to distinguish between expansive and non expansive ettringite based normally in morphology analysis, since the former is characterized by a compressed or compact nature where the needle shapes disappear or are welded together. Furthermore, the use of other techniques, like X-ray diffraction or micro-XRF, has been limited because the compressed or compact ettringite is badly crystallized or even amorphous and the elemental composition is similar and therefore it is difficult to detect. This article presents a methodology for the diagnosis of DEF using polished concrete thin sections and combining polarised and fluorescence light optical microscopy with SEM-EDS.
Year: 2009
Number Pages:
6.
Author(s): Matos, L.; Santos Silva, A.; Soares, D.; Salta, M. M.; Mirão, J.; Candeias, A. E.
Keywords: Concrete; Fluorescence microscopy; Petrographic examination; Scanning electron microscopy; Delayed ettringite formation
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The influence of the geometric scale model on the physical modelling of the wave propagation and breaking in a flume
This paper describes the set of model scale experiments carried out at the National Civil Engineering Laboratory (LNEC) that aims at simulating, using different model scales, the wave propagation along a constant slope bottom that ends on a sea wall coastal defence structure, a common structure employed in the Portuguese coast. This study focuses especially on the complex physical processes involved in the breaking zone and related to wave-structure interaction (such as wave induced pressures at the structure, run-up levels and wave overtopping). The experiments were performed for different incident wave conditions (regular and irregular) and at several different model scales: 1:10, 1:20, 1:30, 1:40 and 1:60. Measurements of the free surface elevation were made on 26 different locations using wave gauges. Moreover, 30 repetitive tests for a selected wave condition were performed to evaluate the error associated to the signal conversion and its propagation on the calculation of derivative variables. A statistical analysis of the free surface elevation data for the different incident wave conditions for the different model scales with regular and irregular waves is presented. That will permit to evaluate the influence of the geometric scale model and the type of waves (regular or irregular) on the physical model results. Moreover, it was performed a statistical analysis to evaluated the variability of the measurements.
Year: 2009
Number Pages:
formato electrónico.
Author(s): Lemos, R.; Fortes, C. J. E. M.; Gil, L.; Neves, M. G.
Keywords: Comibbs project; Wave breaking; Physical models
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The Portuguese Building Regulation System: A Critical Review
Purpose
Year: 2009
Number Pages:
156-171 p..
Author(s): Branco Pedro, J.; Meijer, F. M.; Visscher, H. J.
Editor: Paul Chynoweth
Keywords: Portugal; Control system analysis; Technical regulations; Buildings
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The use of impulse ventilation to control pollution in underground car parks
The ventilation of underground car parks is important to avoid health problems with the inhalation of combustion products released by car engines, in special CO (that is commonly used as the indicator of indoor air quality). In last years, a new mechanical ventilation system appeared, based on the use of axial ventilators (jet fans) suspended under the car park ceiling. In this paper the flow generated by jet fans and their effects on the pollutants are studied. It is concluded that jet fans may have a pumping effect entraining the surrounding contaminated air into the jet. In this way jet fans are able to restrict the dispersion of the contaminants, provided that the exhaust flow rate from the car park is not lower than the jet flow rate. Impulse ventilation may also provide fast dilution of the local pollution peaks, but in this case the removal efficiency will be low. This paper also suggests criteria to define the distance between jet fans.
Year: 2009
Number Pages:
57-74pp.
Author(s): Viegas, J.
Editor: VEETECH Ltd.
Keywords: Cfd; Jet fan; Underground car park; Impulse ventilation
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Thermal comfort criteria and building design: Field work in Portugal
The present paper focuses on the issue of thermal comfort adaptive criteria and its relevance to the implementation of passive design strategies, in the context of a
Year: 2009
Number Pages:
2357-2361pp.
Author(s): Correia Guedes, M.; Matias, L.
Editor: Elsevier - Renewable Energy
Keywords: Adaptive model; Thermal comfort
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Three-dimensional modeling of the lower trophic levels in the Ria de Aveiro (Portugal)
Thewater and the ecosystem dynamics of the Ria de Aveiro, a shallow, multi-branch lagoon located on the northwest coast of Portugal, are simulated using a newfully coupled 3Dmodeling system. This model couples the hydrodynamic model SELFE (semi-implicit Eulerian-Lagrangian finite element) and an ecological model extended from EcoSim 2.0 to represent zooplankton dynamics. The model application is based on an unstructured grid spatial discretization, which is particularly appropriate for this system given its complex geometry. The baroclinic circulation is calibrated and validated for different environmental conditions, leading to velocity errors smaller than 5 cm/s across the lagoon. Ecological simulations, focused on zooplankton dynamics represented by a site-specific formulation, are then presented and compared against field data for two contrasting environmental conditions: Autumn 2000 and Spring 2001. Results show that the fully coupled model is able to reproduce the dynamics of the ecosystem in the Spring 2001, fitting the model results inside the range of data variation. During this period zooplankton differences between data and model results are of about 0.005mgC/l (60%), while other ecological tracers
Year: 2009
Number Pages:
1274
Author(s): Rodrigues, M.; Oliveira, A.; Queiroga, H.; Fortunato, A. B.; Zhang, Y. J.
Editor: Ecological Modelling
Volume:
220.
Keywords: Zooplankton dynamics; Hydrodynamics; Channels; Unstructured grids; 3d coupled model; Eco-selfe; Coastal lagoon; Ria de aveiro
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Tidal and river discharge forcing upon water and sediment circulation at a rock-bound estuary (Guadiana estuary, Portugal)
The relative impacts of tidal (neap, spring) and river discharge (including a flood event) forcing upon water and sediment circulation have been examined at the rock-bound Guadiana estuary. Near-bed and vertical profiles of current, salinity, turbidity, plus surface suspended sediment concentrations (SSC, at some stations only), were collected at the lower and central/upper estuary during tidal and fortnightly cycles. In addition, vertical salinity and turbidity profiles were collected around high and low water along the estuary. Tidal asymmetry produced faster currents on the ebb than on the flood, especially at the mouth. This pattern of seaward current dominance was enhanced with increasing river flow, due to horizontal advection that was confined within the narrow estuarine channel. The freshwater inputs and, at a degree less, the tidal range controlled the vertical mixing and stratification importance. Well-mixed (spring) and partially stratified (neap) conditions alternated during periods of low river flows, with significant intratidal variations induced by tidal straining (especially at the partially stratified estuary). Highly stratified conditions developed with increasing river discharge. Intratidal variability in the pycnocline depth and thickness resulted from current shear during the ebb. A salt wedge with tidal motion was observed at the lower estuary during the flood event. Depending on the intensity of turbulent mixing, the residual water circulation was dominantly controlled either by tidal asymmetry or gravitational circulation. The SSC was governed by cyclical local processes (resuspension, deposition, mixing, advection) driven by the neap-spring fluctuations in tidal current velocities. More, intratidal variability in stratification indicated the significance of tidal pumping at the partially and highly stratified estuary. The estuary turbidity maximum (ETM) was enhanced with increasing current velocities, and displaced downstream during periods of high river discharge. During the flood event, the ETM was expelled out of the estuary, and the SSC along the estuary was controlled by the sediment load from the drainage basin. Under these highly variable river flow conditions, our observations suggest that sand is exported to the nearshore over the long-term (>years).
Year: 2009
Author(s): Garel, E.; Pinto, L.; Santos, A.; Ferreira, Ó.
Editor: Estuarine, Coastal and Shelf Science
Volume:
Volume 84, Issue 2.
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Um(a) NAU com 40 anos, parte I
N/A
Year: 2009
Number Pages:
9 p..
Author(s): Baptista Coelho, A.
Editor: Grupo Habitar
Keywords: Pesquisa em arquitectura; Nau do lnec; Investigação em urbanismo; Investigação arquitectónica
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Um(a) NAU com 40 anos, parte II
N/A
Year: 2009
Number Pages:
19 p..
Author(s): Baptista Coelho, A.
Editor: Grupo Habitar
Keywords: Pesquisa em arquitectura; Núcleo de arquitectura e urbanismo; Nau do lnec; Investigação em urbanismo; Investigação em arquitectura; Investigação arquitectónica; Nau
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