5678 research outputs found
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Finding new trends through data analytics in infrastructure asset management – rehabilitation investments versus operational management
No full textWater utilities sustainable management is a leading challenge in which data and information analysis play a key role. Nowadays data generated in information systems is too much, evolves too fast and is too diverse, requiring innovative information processing forms to enhance organization’s management. Driven by reporting requirements, legal obligations in developing Infrastructure Asset Management (IAM) plans and the implementation of an asset management policy inside the Group, AGS (Administração e Gestão de Sistemas de Salubridade, S.A.) designed, developed and implemented a dynamic tool to support data management and information analysis. Based on tool’s capabilities, a case study is presented, analysing rehabilitation investment impact on water systems performance. Results have shown that the relations between rehabilitation rates and non-revenue water (NRW) levels tend to normalize, being possible to establish the financial effort to reduce NRW in a given value for the case study’s period.8pComunicação apresentada na conferência LESAM 2015, IWA, Yokohama, Japan, 17-19 NovembroDHA/NE
Design and construction of backfills for railway track transition zones
No full textThe initial geometry of a railway track continually degrades over its life-cycle. Changes in the track alignment give rise to
variations in the dynamic axle load which accelerate track degradation, with consequences for maintenance and avail-
ability of the line. This behaviour is particularly evident at some critical locations that are associated with abrupt changes
in the track’s vertical stiffness, such as transitions to bridges or other structures. In order to mitigate this problem,
careful design and construction is required, for which several recommendations have been suggested in the literature.
However, studies based on the maintenance records of existing high-speed lines have shown that the problem of track
degradation associated with stiffness variations is far from being solved. This paper presents a short review on the design
of transition zones. A case study on the design and construction of a transition zone on a new Portuguese railway line is
analysed. Results of conventional laboratory and cyclic load triaxial testing on granular materials and in situ mechanical
characterization of the layers are presented. Relevant aspects regarding the construction are addressed and discussed.
The results obtained at the substructure level seem to indicate that the design of the transition zone was successful in
minimizing settlement and achieving a gradual stiffness increase as a bridge is approached.9358-70 (13P)Published online before print; August 28, 2013, doi: 10.1177/0954409713499016; Copyright © 2013 by Institution of Mechanical EngineersDT/NIFProceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transi
Experimental research with salt crystallization in historic Portuguese azulejos
No full textFor five centuries, azulejos have been widely used in Portugal as decorative architectural linings. The most serious form of degradation is the spall of the glaze containing the decoration. Crystallisation of soluble salts is often pointed as its main cause, but that remains yet to be proven. Indeed, there are publications on many simulations of salt decay in porous materials such as stone or brick. However, azulejos have a largely impermeable surface which excludes the possibility of through evaporation, and thus represent a very different physical model.
This communication reports a study on the physical degradation of azulejos caused by cycles of dissolution and re-crystallisation of sodium chloride (NaCl). Ageing tests were carried out on 26 Portuguese azulejos from the 17th to the 19th century, some of which with original manufacturing defects or with varying degrees of decay arising from their in situ usage.
Ageing cells were developed to try to reproduce conditions to which azulejos are subjected to in walls, namely imbibition from the backside and drying through the glazed surface. The azulejos initially contaminated with a NaCl saturated solution were submitted to 81 accelerated full cycles of imbibition/drying.
The tests caused damage in some cases- sometimes very extensive damage indeed- particularly settling in areas where the solution could evaporate freely, but failed to reproduce other sorts of damage often found in situ. It did not verify that the action of NaCl alone could trigger an accelerated loss of glaze in a healthy and properly applied azulejo. Moreover, we concluded that the decaying action of soluble salt is facilitated by pre-existing degradation or defects.129-132pp.Abstract in English and full text in Portuguese. Participação do LNEC ao abrigo do Proc. 0202/111/19014 (infraestrutura IPERION-CH.pt)DM/NBPCProceedings of the International Conference Glazed Ceramics in Architectural Heritage (GlazeArch 2015
Flooding hazard in the Tagus estuarine area: The challenge of scale in vulnerability assessments
No full textThis paper describes the methodology of the vulnerability assessment to flooding in an
estuarine context and presents the final results for the Tagus River estuary, in the metropoli-
tan region of Lisbon (Portugal). Performing a local study adapted to a specific type of hazard
posed two initial methodological challenges: the selection of the unit of analysis and the
identification of the pertinent and available variables. Both challenges were addressed
assuming that the area to be assessed should also include the units outside the inundated
area, a buffer zone that would include areas indirectly affected. The application of the
statistical procedures established in the SoVI1 methodology indicate that certain widely used
variables in vulnerability assessments on smaller scales are inadequate at the statistical block
scale and that specific variables must be defined and integrated to represent more broadly the
dimensions of vulnerability related to social assistance, infrastructures and commutability.
The extracted principal components identified the vulnerability drivers in the riverside
and surrounding areas. These drivers identify the urban context, the family structure, and
the socio-economic condition expressed in terms of housing characteristics, education,
mobility and commuting as the dimensions that most differentiate territorial and individuals’
vulnerability. Applications of vulnerability research in risk management are found in
the fields of risk communication, stakeholders’ involvement and strategic and operational
planning in emergency planning as in other concurring sectors.238-255ppDHA/NECEnvironmental Science & Polic
Digital image processing: application to automatic classification of tile panel pathology
No full textDigital image processing (DIP) is a technique to extract information from images with application on several areas of engineering and architecture, which can be used as a tool to map pathologies on tile panels. This paper presents the processing tasks that must be performed on a tile panel image, to perform corrections on the image, to delineate the pathologies and to classify it´s typology, in order to produce the graphical registration of anomalies or monitor multitemporal changes. Several types of anomalies could be identified like, tile rotation, glaze lack, glaze pores, craquelé, open joints, repaired joints, etc.. The images for these applications are digital photographs and the acquisition must follow some specifications to obtain accurate results. Depending of the characteristics of the tile panels (like repetitive patterned or historical) different strategies must be implemented for automatic pattern delineation and classification. Object oriented image analysis (OBIA) methodologies and a picture element (pixel) based system, named GeMAPA, developed at LNEC’ LabImagem, are presented. These studies are developed at LNEC´s Digital Image Processing Laboratory (LabImagem) under project «Numerical Images: applications to engineering» of LNEC’s Research and Innovation Plan 2012-2020.7pDBB/NG
Determinação automática de limiares para classificação de conjuntos multitemporais de imagens de satélite
No full textOs métodos de classificação orientados por objetos apresentam uma eficácia elevada quando aplicados a imagens de satélite. No entanto, os algoritmos desenvolvidos para a classificação de uma determinada imagem apresentam um desempenho mais baixo quando aplicados a uma imagem da mesma área geográfica, adquirida noutra época, ou a uma imagem de outra área geográfica. O principal obstáculo à repetibilidade do algoritmo é a identificação dos valores dos limiares de corte a aplicar às funções de classificação, que é necessário adaptar a cada imagem, o que torna o processo subjetivo e demorado.
Foi desenvolvido um método, baseado na análise por componentes principais, que permite o ajuste automático dos limiares adequados para a classificação de imagens da mesma área geográfica adquiridas noutra época. Os dados de entrada do algoritmo são os limiares selecionados visualmente para a classificação de quatro imagens de referência. Através desses limiares e de parâmetros conhecidos que caraterizam as imagens e as condições em que estas foram adquiridas, o algoritmo calcula os limiares adequados para a classificação de um novo conjunto de imagens.
O algoritmo foi testado em imagens SAR de amplitude adquiridas pelos satélites Envisat e ERS-2 (aplicado à identificação de áreas inundadas) e em imagens óticas adquiridas pelo sensor do Landsat 8, tendo ficado demonstrada a sua utilidade na automatização do processo de ajustamento dos limiares a novas imagens, de forma objetiva e expedita, promovendo a repetibilidade da metodologia de classificação desenvolvida.7pDBB/NG
Utilização do cluster Medusa a partir de ambiente Windows com o Eclipse
No full textEste registo pertence ao Repositório Científico do LNECO LNEC mantém desde 2007 uma infraestrutura cluster, o Medusa, com o objectivo de proporcionar aos seus investigadores acesso a capacidades modernas de computação científica para resolução de problemas de engenharia. No entanto, algumas características do cluster têm atrasado a sua adoção generalizada pelos investigadores, sendo uma delas a necessidade de utilizar um ambiente Linux para interagir com o Medusa da forma convencional. Neste relatório é introduzida uma alternativa a esta forma convencional de utilização do Medusa, recorrendo ao ambiente de desenvolvimento integrado (IDE) Eclipse e à ferramenta Parallel Tools Platform (PTP), que permite evitar a interacção com o ambiente Linux e utilizar o cluster a partir de um ambiente mais familiar, como o Windows. A expetativa é que esta solução alternativa contribua para facilitar a transição dos investigadores para o Medusa, conduzindo a um melhor aproveitamento dos recursos computacionais disponíveis no laboratório e à exploração de novas possibilidades no domínio da resolução de problemas de cálculo complexos.Núcleo de Tecnologias de Informação em Engenharia Civil / NÃO CONFIDENCIALCD/NTIE
Forecasting the impact of storm episodes on beaches: present limitations
No full textEste registo pertence ao Repositório Científico do LNECThe application of credible morphodynamic forecast models to provide evidence-based information for coastal managers making decisions for re-profiling the beach and thus increase coastal resilience by restoring the sediment balance and providing space for coastal processes is a relevant issue since the future risk of coastal storm impacts is likely to increase. The study exposes the practical limitations and inevitable uncertainties found in the application of two state-of-the-art process-based morphodynamic numerical models to an Atlantic urban sandy beach under extreme wave energy and surge conditions. The erosion of the foreshore and backshore of this particular beach was characterised as function of the intensity and duration of the hydrodynamic forcing parameters. The models performance was evaluated and compared. A major conclusion achieved was that in order to obtain reliable simulations of the morphodynamics during high energy coastal events it is necessary to further develop and apply non-intrusive monitoring techniques, which enable accurate monitoring in such adverse environments, to capture the physics in those conditions and load correctly the numerical models. There is an urgent need to overcome the present limitation in order to achieve a higher level of reliability in beach erosion impact forecasts.DHA/NE
Rubble-mound breakwater armour units displacement analysis by means of digital images processing methods in scale models
No full textRubble-mound structures are commonly used for coastal and port protection and needs a
properly design as well as inspection and maintenance during its lifetime. The design of such breakwaters
usually requires a physical scale model to be tested under different irregular incident wave and tide
conditions in order to evaluate its hydraulic and structural behaviour, namely the stability of the proposed
design. Armour units displacement and fall analysis in physical models are then a key point in the design
verification and usually requires a trained technician. In this work, an algorithm made in Matlab® is
presented, consisting in digital images processing and analysis which allows automatic and precise
displacement detection as well as its location in time and space. For a selected displacement, it is also
possible to characterize it.171-184ppDHA/NP
Análise da estabilidade de uma barragem gravidade antiga de alvenaria de pedra
No full textApresenta-se a análise da estabilidade da barragem do Covão do Ferro, uma estrutura de gravidade de alvenaria de pedra argamassada, localizada a elevada altitude na Serra da Estrela, em Portugal, com altura máxima de 32,5 m e um desenvolvimento do coroamento de cerca de 400 m. A barragem foi reabilitada entre 2004 e 2006 com o objetivo de repor as condições de segurança estrutural. As principais obras incluíram a injeção de calda de cimento no corpo da barragem e no maciço de fundação, a instalação de uma geomembrana de PVC no paramento de montante e o reforço do sistema de drenagem através da abertura de novos drenos.
A análise estrutural realizada, para as condições existentes antes da reabilitação, permitiu estudar o efeito das pressões internas e da subpressão na estabilidade local e global da barragem bem como os possíveis mecanismos de rotura.13pDBB/N