Artigos de Revista
Info
Corrosão sob tensão em ancoragens
A estabilidade duma estrutura ancorada em terreno é condicionada pela integridade das ancoragens cujo desempenho é função dos detalhes de projeto, materiais empregues, características do meio envolvente, técnicas construtivas e controlo de qualidade, em particular, dos sistemas de proteção contra a corrosão. Diversos erros tais como falhas na fase de projeto, incorreta execução ou a utilização de materiais inadequados podem conduzir a uma deficiente proteção anticorrosiva, que frequentemente está na origem da rotura destas ancoragens. No presente caso de estudo, a rotura de armaduras de aço em ancoragens ocorre por um processo de corrosão sob tensão, devido a fragilidades do seu sistema de proteção anticorrosivo nas proximidades de zonas de acoplamento das armaduras sob a interface entre os distintos componentes do sistema de proteção.
Ano: 2014
Número Páginas:
5-11.
Autor(es): Correia, M. J.; Salta, M. M.; Baptista, A. M.
Revista: Corrosão e Protecção de Materiais
Editor: LNEG - Laboratório Nacional de Energia e Geologia, I.P.
Volume:
33.
Keywords: Fratografia; Barras de Ancoragem; Corrosão sob Tensão; Proteção Anticorrosiva
Info
Corrosão sob tensão em ancoragens
A estabilidade duma estrutura ancorada em terreno é condicionadapela integridade das ancoragens cujo desempenho é função dosdetalhes de projeto, materiais empregues, características do meioenvolvente, técnicas construtivas e controlo de qualidade, em particular,dos sistemas de proteção contra a corrosão. Diversos erros tais comofalhas na fase de projeto, incorreta execução ou a utilização de materiaisinadequados podem conduzir a uma deficiente proteção anticorrosiva,que frequentemente está na origem da rotura destas ancoragens.No presente caso de estudo, a rotura de armaduras de aço emancoragens ocorre por um processo de corrosão sob tensão,devido a fragilidades do seu sistema de proteção anticorrosivo nasproximidades de zonas de acoplamento das armaduras sob a interfaceentre os distintos componentes do sistema de proteção.
Ano: 2014
Número Páginas:
7p.
Autor(es): Correia, M. J.; Salta, M. M.; Baptista, A. M.
Revista: CORROSÃO E PROTECÇÃO DE MATERIAIS
Editor: LNEG
Volume:
VOL. 33, Nos 1-2.
Keywords: Barras de ancoragem; Corrosão sob tensão; Proteção anticorrosiva; Fratografia
Info
Corrosion Protection of Hot Dip Galvanized Steel in Mortar
Corrosion of steel in concrete is one of the major causes of structure degradation, requiring expensive maintenance. The using of hot dip galvanized steel (HDGS) has been recognized as one effective measure to increase the service life of reinforced concrete structures in marine environmental. However, HDGS corrodes in contact with high alkaline environment of fresh concrete. Although this initial corrosion process allows the formation of a protecting layer barrier, the corrosion that occurs initially is harmful and chromate conversion layers are usually used to prevent it. Due to toxicity of Cr(VI), these kinds of pre-treatments have been forbidden and hybrid coatings have been proposed as alternatives. To evaluate the performance of these coatings, beyond the laboratory characterization, in situ tests in real conditions should be performed. An electrochemical system to measure the macrocell current density (igal) was designed to evaluate the degradation of HDGS coated samples with different organic-inorganic hybrid films, embedded in mortar during 70 days, using an automatic data acquisition system. This system revealed to be feasible and highly sensitive to coatings degradation. Also,allow distinguishing different hybrid coatings with different thicknesses.
Ano: 2014
Número Páginas:
10.
Autor(es): Figueira, R. B.; Pereira, E. V.; Silva, C. J. R.; Salta, M. M.
Revista: Portugaliae Electrochimica Acta
Editor: Sociedade Portuguesa de Electroquimica
Volume:
31 (5).
Keywords: Corrosion of steel in concrete; Corrosion protection; Sol-gel; Galvanized steel
Info
Crack-path field and strain-injection techniques in computational modeling of propagating material failure
The work presents two new numerical techniques devised for modeling propagating material failure, i.e. cracks in fracture mechanics or slip-lines in soil mechanics. The first one is termed crack-path-field technique and is conceived for the identification of the path of those cracks, or slip-lines, represented by strain-localization based solutions of the material failure problem. The second one is termed strain-injection, and consists of a procedure to insert, during specific stages of the simulation and in selected areas of the domain of analysis, goal oriented specific strain fields via mixed finite element formulations. In the approach, a first injection, of elemental constant strain modes (CSM) in quadrilaterals, is used, in combination of the crack-path-field technique, for obtaining reliable information that anticipates the position of the crack-path. Based on this information, in a subsequent stage, a discontinuous displacement mode (DDM) is efficiently injected, ensuring the required continuity of the crack-path across sides of contiguous elements. Combination of both techniques results in an efficient and robust procedure based on the staggered resolution of the crack-path-field and the mechanical failure problems. It provides the classical advantages of the
Ano: 2014
Número Páginas:
289-348pp.
Autor(es): Oliver, J.; Dias, I. F.; Huespe, A.E.
Revista: Computer Methods in Applied Mechanics and Engineering
Editor: ELSEVIER
Volume:
274.
Keywords: Embedded discontinuities; Strain injection; Crack-path field; Strong discontinuities; Computational material failure; Fracture
Info
Cryptotermes brevis (Isoptera: Kalotermitidae) in the Azores: Lessons After 2 yr of Monitoring in the Archipelago
The dispersal flights of West Indian drywood termite, Cryptotermes brevis (Walker) (Isoptera: Kalotermitidae) were surveyed in the major cities of Azores. The sampling device used to estimate termite density consisted of a yellow adhesive trap (size 45 by 24 cm), placed with an artificial or natural light source in a dark attic environment. In addition, data from two other projects were used to improve the knowledge about the geographical distribution of the species. The level of infestation in the two main Azorean towns differed, with high levels in the houses of Angra do Hero
Ano: 2014
Número Páginas:
7pp.
Autor(es): Borges, P.; Guerreiro, O.; Ferreira, M.; Borges , A.; Ferreira , F.; Bicudo , N.; Lina Nunes; Marcos, R.; Arroz, A.; Scheffrahn, R.; Myles, T.
Revista: Journal of Insect Science
Editor: Oxford University Press em parceria com o Entomological Society of America
Volume:
vol 14.
Keywords: Isoptera; Blattodea; Invasive species; Macaronesia; Urban pest management
Info
Data Management with Risk Management in Engineering and Science Projects
Engineering and Science projects are facing new data management challenges, which are currently being addressed through the development of data management plans. However, project stakeholders are unable to proper assess if their plan is representative of good data management practices. To address this issue, we propose a risk management framework to assist the definition of a data management plan in engineering and science projects. To validate our proposal, we present an application to a civil engineering project concerning dam safety.
Ano: 2014
Número Páginas:
49-66pp.
Autor(es): Vieira, R. J. C.; Ferreira, F.; Barateiro, J.; Borbinha, J. L.
Revista: New Review of Information Networking
Keywords: Risk management framework; Risk management; Data management plan; Data management; Engineering; Science
Info
Delamination of Ançã limestone due to sodium sulfate under different environmental conditions as studied by nuclear magnetic resonance
Sodium sulfate is one of the most damaging and complex salts typically involved in the deterioration of our architectural heritage. One of the main difficulties is to determine which of its crystalline phases, that is, thenardite, mirabilite, or the metastable heptahydrate, will precipitate under certain conditions. Indeed, there is a significant range of temperature and relative humidity in which these phases can crystallize. Furthermore, one precipitated crystalline phase may under certain conditions transform to another one. Here, we show that nuclear magnetic resonance can be successfully used to nondestructively define the phase being precipitated. We investigate delamination of Ançã limestone due to sodium sulfate crystallization, a type of decay which is representative of those occurring in real constructions. The decay was achieved during isothermal drying of stone specimens under different environmental conditions. The work allowed concluding that both mirabilite and heptahydrate can be responsible for this type of decay in different conditions. The heptahydrate tends to crystallize when there is no previous presence of mirabilite crystals in the porous material.
Ano: 2014
Número Páginas:
19.
Autor(es): Brito, V.; Saidov , T.; Gonçalves, T. D.; Pel, L.
Revista: Journal of Building Physics
Editor: SAGE
Volume:
http://jen.sagepub.com/content/early/2014/07/29/1744259114543981.
Keywords: Nmr; Nuclear magnetic resonance; Ançã limestone; Heptahydrate; Thenardite; Mirabilite; Sodium sulfate; Soluble salts; Salt decay
Info
Demonstrating managed aquifer recharge as a solution for climate change adaptation: results from Gabardine project and asemwaterNet coordination action in the Algarve region (Portugal)
In the Algarve southern Portugal region, Managed Aquifer Recharge (MAR) research activities have been developed to provide not only water surplus storage in aquifers during wet years, focusing in the Querença-Silves aquifer (FP6 ASEMWATERNet Coordination Action), but also groundwater quality rehabilitation in the Campina de Faro aquifer (FP6 Gabardine Project). Following MAR research potentialities in southern Portugal, this paper describes the objectives, conceptual demonstration, background and capabilities of one of the selected Circum-Mediterranean pilot sites (in Portugal) that will be researched in the new FP7-ENV-2013-WATER-INNO-DEMO MARSOL project, which started Dec. 1st, 2013. In the Algarve pilot site, severalcase-study areas will be located in the Querença-Silves aquifer and in the Campina de Faro aquifer
Ano: 2014
Número Páginas:
15-22pp.
Autor(es): Lobo Ferreira, J. P. C.; Leitão, T. E.
Revista: Acque Sotterranee - Italian Journal of Groundwater (2014)
Keywords: Campina de faro aquifer; Geophysical assessment; River bed infiltration experiments; Climate change adaptation; Managed aquifer recharge
Info
Development of an oil spill hazard scenarios database for risk assessment
The occurrence of oil spills in coastal regions may have catastrophic consequences on the environment and severesocio-economic impacts. This work presents a new methodology to evaluate the risk associated with oil spills in coastalzones and estuaries, and illustrates its application in a coastal lagoon (Ria de Aveiro, Portugal). A ranked list of thehydrodynamic scenarios under which oil spills are most likely generated through the analysis of 33 years of wave andwind data, retrieved from the ERA-INTERIM project database, and from the analysis of oil spills that occurred in theAtlantic Iberian shelf. Considering six spill locations and a single oil type spill inside the Aveiro harbor, the databaseresulted in approximately 3500 simulations. Hydrodynamic simulations were made with the MORSYS2D modelingsystem, a soft coupling of the hydrodynamic model ELCIRC and the wave model SWAN. The high-accuracy,unstructured grid, oil fate model VOILS was used in 2D mode to simulate the transport and the oil weathering processesat the surface and in the intertidal areas. The hazard assessment analysis included the determination of the trajectory ofthe plumes, the shoreline retention areas affected by the oil and their oil exposure time. Time evolution of the oilproperties, such as the oil evaporation rate and emulsification processes of the mixture, are provided to support clean-upoperations, as well as robustness controls such as oil mass balance.
Ano: 2014
Número Páginas:
p6.
Autor(es): Boer, S.; Azevedo, A.; Vaz, L.; Costa, R.; Fortunato, A. B.; Oliveira, A.; Tomas, L.; Dias, J. M.; Rodrigues, M.
Revista: Journal of Coastal Research
Keywords: Risk assessment; Oil spill modeling; Climatology
Info
Diálogos entre património imaterial e material. O que dizem os artesãos sobre os revestimentos históricos com base em cal
A relação entre património material no caso arquitetónico e imaterial enquanto saber técnico tradicional é um pressuposto que orientou um dos estudos efetuados no âmbito do Projeto Conservação e durabilidade de revestimentos históricos: compatibilidade, técnicas e materiais (LIMECONTECH), desenvolvido no LNEC (Laboratório Nacional de Engenharia Civil) e cofinanciado pela FCT (Fundação para a Ciência e Tecnologia). De espectro mais alargado, este Projeto atendeu também ao estudo das técnicas e materiais tradicionais relacionados com os revestimentos históricos exteriores com base em cal. O principal objetivo deste artigo é apresentar a informação recolhida no âmbito do estudo referido, designadamente no que se refere ao levantamento do conhecimento técnico-tradicional junto de artífices da cal. Visa-se, assim, assinalar o potencial que o levantamento, registo e sistematização deste conhecimento detém para a conservação e restauro do património arquitetónico.
Ano: 2014
Número Páginas:
246-251pp..
Autor(es): Menezes, M.; Veiga, M. R.; Lopes dos Santos, A. R.
Revista: Anuário do Património
Editor: Canto Redondo
Volume:
n.º 2.
Keywords: Conservação; Património; Revestimentos históricos; Saber técnico-tradicional; Testemunho oral
|