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MODELAÇÃO DA INUNDAÇÃO FLUVIAL DO BAIXO MONDEGO
No full textA região do Baixo Mondego tem sido sujeita a inundações cuja extensão importa caracterizar, em particular no contexto da aplicação da diretiva de avaliação e gestão dos riscos de inundações (2007/60/CE), com o objetivo reduzir o risco e as consequências prejudiciais que lhes estão associadas.
O presente trabalho apresenta os resultados da modelação das inundações no Baixo Mondego, no trecho compreendido entre a confluência do rio Ceira e o limite de propagação da maré a jusante. Neste trecho, com cerca de 44.7 km de extensão, o sistema de defesa contra cheias inclui o controlo dos caudais de cheias nas albufeiras a montante, os diques de proteção nas margens direita e esquerda ao longo de cerca de 36 km e o sistema de inundação controlada dos campos.
Neste artigo descreve-se a metodologia utilizada, justificam-se os cenários de simulação adotados, incluindo o funcionamento do sistema de inundação controlada do Baixo Mondego, analisam-se os resultados, dando-se ênfase aos níveis e velocidades atingidos e à propagação das inundações e apresentam-se os mapas de inundação.41-54 ppDOI:10.5894/RH35N2-4)Volume 35, Nº 2DHA/NRERevista de Recursos Hídrico
Non-linear elastic behaviour of unbound aggregates in FEM representing railway transition zones
No full textThe stress dependent behaviour of the unbound granular materials that carry the track,
and the voids that may occur between the base of the sleepers and the ballast, are
the important factors for non-linear track behaviour. On transition zones, where the
track stiffness may rapidly vary and often differential settlements take place between
the stiff structure and the approach section of the track, these aspects are of particular
relevance. Despite the non-linear constitutive behaviour of unbound aggregates, it is
still common practice to consider the linear elastic behaviour for these materials in
the design of transportation infrastructure. The present study focuses on the imple-
mentation of these non-linear aspects in a finite element algorithm for the dynamic
simulation of railway tracks. Linear and nonlinear constitutive laws are used to re-
produce the behaviour of unbound aggregates that comprise the trackbed. Stress and
deformation results are presented and discussed for both linear and non-linear scenar-
ios. The results show that the consideration of these non-linear aspects is relevant for
the modelling of railway transitions.21pDT/NIF20148-11 Apr
Ensaios dinâmicos em paredes de frontal pombalinas
No full textO estudo apresentado neste trabalho teve como objetivo caracterizar experimentalmente o comportamento dinâmico das paredes de frontal Pombalinas, através de ensaios realizados
na mesa sísmica no Laboratório Nacional de Engenharia Civil em Lisboa.
No presente artigo expõem-se as opções que estiveram na base da conceção do modelo das paredes para a realização dos ensaios na plataforma sísmica triaxial. Apresentam-se a conceção do protótipo e a construção dos modelos físicos incluindo a definição da sua geometria, a caracterização dos materiais, os detalhes da sua construção e as dificuldades encontradas nos ensaios.
Por fim apresentam-se os resultados da caracterização modal da estrutura de parede metálica, para avaliar o seu dimensionamento e a sua influência no ensaio. Posteriormente, e com o intuito de avaliar a influência da alvenaria na resposta do modelo, apresenta se o ensaio de identificação modal das paredes só com estrutura de madeira, e o ensaio de identificação do modal do modelo das paredes pombalinas.16pDE/NESD
Salamonde II repowering project: natural flood protection of the outlet structure
No full textThe Salamonde Hydroelectric power scheme is located in the north of Portugal, within the
Cávado river mountainous basin, and is one of the seven powerplants of Cávado-Rabagão-
Homem hydropower system.
The original Salamonde scheme began industrial operation in 1953 and recently EDP took the
decision to repower it by means of a new 209 MW reversible scheme (Salamonde II).
Several scale hydraulic model studies of the main hydraulic structures were performed. The
paper presents the basic design studies and the description of the outlet structure and
downstream channel scale model tests as well as the results obtained.ISBN 978-989-96479-2-3DHA/NRE201414 a 16 de abri
Desenvolvimento do Sistema de Previsão e Alerta de Inundações HIDRALERTA: Caso de Estudo da Costa da Caparica
No full textNesta comunicação faz-se a descrição dos módulos do sistema de previsão e alerta de
galgamento/inundações em zonas costeiras e portuárias, HIDRALERTA. Este sistema, que está em
desenvolvimento, efetua previsões de agitação marítima até 180 horas, e calcula os correspondentes
galgamentos/cotas de inundação recorrendo a modelos numéricos, redes neuronais e/ou fórmulas
empíricas. Sempre que sejam excedidos limites pré-estabelecidos para os galgamentos/cotas de
inundação de cada área da zona de estudo, definidos de acordo com a sua vulnerabilidade, é acionado
o alerta. Ilustra-se a aplicação deste sistema na Costa da Caparica, cujos acontecimentos recentes de
galgamento/inundação evidenciam as suas potencialidades.60147-150ppDHA/NPE201424 a 26 de junh
On pressure disturbance waves
No full textPressure disturbance waves are computed via a fully nonlinear, unsteady, boundary integral formulation for various Froude numbers. Three moving pressure distributions are introduced in the numerical model to evaluate the produced wave patterns in a channel. For Froude numbers equal to one, classical runaway solitons are obtained on the fore of the moving pressure patch whereas "stern" waves are radiated away. "Step-like" pressure distributions give different responses to the free-surface flow, with upward breaker jets and steeper "stern" waves. For supercritical and subcritical flows, steady solitons and stationary trenches moving at the same speed of the pressure distribution are obtained, respectively. Nonlinear results show that the wave field is significantly affected by the chosen moving pressure distribution, with breaking "bow" waves and steeper "stern" waves when "step-like" pressure functions are used.69-74ppDHA/NP
Experimental investigation on limitation of the progression of internal erosion in zoned dams
No full textTwo mechanisms limiting the progression of internal erosion in zoned dams, potentiated by the presence of materials located upstream of a damaged core are investigated. These are the flow restriction and crack filling actions. The former is related with the ability of the upstream soil restricting the flows passing through a flaw in the core. The latter involves transport of particles from the upstream zone into a flaw in the core, up to a downstream granular zone. A new apparatus is developed from scratch. It allows carrying out two innovative laboratory tests: the Flow Limitation Erosion Test (FLET) and the Crack Filling Erosion Test (CFET). Following an extensive testing programme on thirteen upstream materials, two cores, and two downstream filters, experimental observations and physical descriptions are presented. The potential soil behaviour patterns are described. The apparatus can assess whether erosion in the core stops, slows down, or progresses. The flow restriction action is governed by grading, plasticity and compaction characteristics of the upstream soil. In gap-graded with 5% of fines, the hydraulic loading and type of fines are critical. Crack filling by granular soils occurs rapidly, being governed by the sand and fines content of the upstream soil, and an effective grain diameter (D15F) of the filter. Rules for preliminary estimation of the likelihood of occurrence of the studied actions are also proposed.DG/NGO
Overtopping hazard on a rubble mound breakwater
No full textA major concern of coastal engineering is not only to access the damage to coastal structures by severe wave overtopping, but also the hazard imposed to users. Local hazard is often associated to the volume of overtopping water per unit of time (called overtopping discharge). Despite two decades of intensive research, it is yet not fully clear to practitioners what is the best method to compute the discharge parameter and its application on the assessment of local hazard. This work provides insight into the overtopping characterization in rubble mound breakwaters, by distinguishing different methods to assess hazardous overtopping. Fieldwork was conducted over a tidal cycle in a breakwater located at Albufeira Harbour (South coast of Portugal) under storm conditions (Hso~ 3 m; Tp ~ 9 s). Mean overtopping discharges were calculated from field measurements of flow depths and velocities at the breakwater slope armour and at the impermeable crest. Two different velocities were calculated: overtopping leading-edge velocity and overtopping peak velocity. The two methods provided similar results, with higher velocities occurring during high-tide (between 2 and 10 m/s). Mean overtopping discharges at the beginning of the impermeable crest ranged between 0.2 and 0.8 l/s/m. Under the measured hydrodynamic conditions, the breakwater offers risk to all types of pedestrians.
Additionally it is shown that field measurements compare relatively well with empirical prediction methods (for the overall analysed overtopping events), namely the corrected NN_OVERTOPPING2 neural network tool. Besides contributing to the overall database on wave overtopping in coastal structures, the presented results can also be used for calibration and validation of overtopping evaluation methods (empirical formulae, artificial neural networks and numerical and physical models).53247-252ppSpecial Issue No. 70DHA/NPEJournal of Coastal Researc
Improvement of the Lateral Distribution Method based on the mixing layer theory
No full textThe accurate prediction of depth-averaged streamwise velocity, boundary shear stress and lateral shear
stress are important requisites for the estimation of the flow depth associated with flood events in compound
river channels composed of main channel and floodplain. This engineering problem may be tackled
through the analytical solution of the depth-averaged momentum equation. Under uniform flow, this
solution relies on the calibration of three descriptors of the bottom friction, secondary currents and lateral
shear stress. In this paper, the analytical solution materialized in the Lateral Distribution Method is
revisited through the consideration of a new panel division. Accurate measurements of streamwise and
spanwise velocities as well as of boundary shear stress are used to obtain new predictors of the coefficients
describing the effects of bottom friction, secondary currents and lateral shear.
The new lateral division of the compound channel into four panels is physically based on the mixing
layer width, which is computed by an iterative procedure easily implemented in practical applications.de 159 a 16769DHA/NREAdvances in Water Resource
Alcohol-Aminosilicate Hybrid Coatings for Corrosion Protection of Galvanized Steel in Mortar
No full textOrganic-inorganic hybrid (OIH) matrices were synthesized by sol-gel method and deposited on hot-dip galvanized steel (HDGS)
using a dip-coating process. These OIHs, generally called amino-alcohol-silicates, were synthesized using a functionalized siloxane,
3-glycidoxypropyltrimethoxysilane, and five oligopolymers (Jeffamine) with different molecular weights: 230, 400, 600, 900 and
2000. Besides the five different pure OIH matrix coatings, a similar set of HDGS samples were coated with the OIH matrices doped
with Cr(III), which was tested as a corrosion inhibitor. The OIH coatings were assessed using electrochemical studies, namely
electrochemical impedance spectroscopy, macrocell current density, open circuit potential monitoring and polarization resistance.
The studies were carried out in mortar. Analysis of the results obtained by optical and scanning electronic microscopy methods
were consistent with the data obtained by electrochemical techniques. The HDGS samples coated with OIH matrices showed better
performance when compared with HDGS uncoated samples.Fundação para a Ciência e Tecnologia (FCT) for the PhD grant SFRH/BD/62601/2009. Financial support by Centro de
Química [project FCOMP-01-0124-FEDER-037302 (ref. FCT Pest-
C/QUI/UI0686/2013)-FEDER-COMPETEC349-C362161 (6)DM/NMMJournal of The Electrochemical Societ