Artigos de Revista

A significant number of problems related to concrete deterioration were detected in Portugal and worldwide due to the development of internal expansive reactions (IER). Their negative effect has important economic implications because they are the main cause of degradation of large concrete structures. In addition, the work necessary to remediate the problem involves large areas of reconstruction and complex and expensive rehabilitation techniques and materials. Moreover, IER diminishes the affected structure service life, may involve the interruption of its function and, ultimately, can lead to its decommissioning and demolishing. Therefore, a study is being conducted at LNEC to diminish their negative impact by increasing knowledge on how to reliably assess their extent and potential for future development in existing structures. To study the effect that IER have in the deterioration of concrete, the common practice is to perform tests on specimens exposed to an artificial environment that promotes IER. However, these tests take several months or years to produce results. Thus, this paper presents the preliminary work carried out to devise a method capable of producing internal damage to concrete in a short period and in a way that the produced deterioration affects the concrete mechanical properties similarly to IER.

A new laboratory test, the crack-filling erosion test (CFET), was developed to study crackfilling during the progression of internal erosion in the embankment of zoned dams. Crackfilling involves the transport of eroded material from an upstream zone, through a flaw inthe core, which is then retained by a downstream granular layer. In the CFET, the specimencomprises a core, an upstream shell material, and a downstream filter layer. These arecompacted inside a test apparatus made up of several pieces. The specimen is subjected towater flow through a predrilled hole in the core to simulate a concentrated leak. Sevengranular upstream materials, two core soils, and two granular filters are examined. Followingan extensive testing program, experimental observations and physical descriptions arepresented. Three main types of pattern behaviors are identified: rapid crack filling withalmost

The application of the limit state design (LSD) in the geotechnical area has increased over the last two decades, but this approach is not yet widely used in dam safety evaluation. This study aims to widen the use of the LSD application for large dams, in particular concrete gravity dam foundations. This paper starts with a brief reference to the LSD approach in recently published guidelines for dam design, followed by a detailed description of the LSD formulation when applied to the foundation of concrete dams. The relevance of the joint application of the concepts of ultimate limit states and of numerical methods is highlighted. Comments are made regarding the criteria adopted in order to determine the characteristic values of the material mechanical properties, with an emphasis on discontinuities, taking into account the spatial variability. The sliding safety assessment of the foundation of a concrete gravity dam using the LSD and a discrete element model, both in persistent and in an accidental design situation, is presented. Results led to the conclusion that the LSD methodology may be followed for dam foundation design with the partial factor values prescribed in Eurocode 7.

An accurate assessment of the airflow in naturally ventilated double skin facades (DSF) is crucial for a correct design and performance evaluation. Measuring and predicting DSF airflow is not a straightforward task, given the stochastic nature of the wind, which can assist or oppose the buoyancy force. The present paper resumes the results of airflow measurements inside a naturally ventilated double skin facade using a tracer gas technique. The tests were performed on an outdoor air curtain (OAC) DSF test cell with a movable slat venetian blind. Measurements with no active shading and at night were also performed. Outdoor and test cell air gap temperatures were continuously measured and wind pressure coefficients were determined from wind tunnel tests. Experimental results were then compared to those obtained by a simple model taking into account both thermal and wind effects on the facade. From this comparison discharge coefficients were estimated, which can be used for characterizing the DSF behaviour.

Delamination at the glue lines is a key factor to take into account when assessing glued laminated timber members in service. In order to gain a more objective and wide knowledge about the importance of delamination in relation to its type and extension, a numerical study was developed.Finite element modeling (FEM) was used to evaluate the influence of delamination

Discute-se, em linhas gerais, o proveito da análise das práticas quotidianas para melhor compreender as dinâmicas socio-espaciais de invenção continuada do património numa cidade em acelerado processo de transformação. Este objetivo de cunho mais abrangente é aqui introduzido a partir de comentários específicos e relacionados com o Bairro da Mouraria, em Lisboa. Isto porque, ao considerar este bairro como caso de discussão, chama-me particular atenção uma certa centração naquilo que o bairro foi (ou teria sido) – o passado – e naquilo que se pretende como horizonte futuro para,o bairro – o projeto. Essa espécie de lógica de ocultação do quotidiano – algures perdido entre um passado idealizado (mas que pode também ser rejeitado) e um sedutor horizonte futuro que, em grande medida, se delineia por contraposição ao que é indesejável (e relacionado com um tempo-espaço passado, mesmo que próximo) – conduz-me a pensar sobre o interesse em investir num conhecimento que contribua para melhor compreender-se os sentidos e significados quotidianos do viver o bairro, a cidade, como se de uma reivindicação ao direito à visibilidade do quotidiano também tratar-se.

Structural robustness has become an important design variable. However, based on the existing definitions of structural robustness it is often difficult to analyse and evaluate structural robustness, and sometimes not efficient since they mix structural robustness with several other structural variables. This paper concerns the development of a new structural robustness definition, and structural robustness and structural fragility indices. The basis for the development of the new indices is the analysis of the damage energy of structural systems for a given hazard scenario and involves a criterion to define an

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This paper presents a novel methodology for evaluating the efficiency of indoor domestic water use based on performance assessment functions that convert state variables (e.g. flow rate, volume) into performance indices ranging from 0 (the lowest performance) to 300 (excellent performance). Performance functions have been developed for the most common water use devices in the household. An overall household water use index was obtained from the individual water use device indices by weighting each device in accordance with the consumption structure of the household. The application of this methodology to 43 households allowed the quantification of potential water savings and the identification of device-specific measures to increase the water use efficiency

O Forte de Nossa Senhora da Graça localiza-se no Monte de Nossa Senhora da Graça, a norte da cidade de Elvas (figuras 1 e 2) [1][2]. É construído no final do sécula XVIII classificado como Património Nacionalem 1910 e como Património Mundial, pela UNESCO, em 2012.Na construção do forte utilizaram-se pedras e terras sobrantes das minas abertas no maciço rochoso do monte, assim como outros materiais existentes nas proximidades do local da construção,tal como areia e material cerâmico [1][2]. No âmbito da sua nomeação pela UNESCO, em 2012, em conjunto com as restantes fortificações de Elvas, como Património Mundial, foi implementado um plano de conservação e restauro do Forte que envolve, entre outras atividades, uma caracterização detalhada dos materiais empregues na sua construção.