Artigos de Revista

This study proposes an alternative approach to modeling the failure mechanisms of brickwork assemblages under combined shear

In the framework of a third Tagus River crossing, through an immersed tunnel, advancedlaboratory tests were performed on its highly liquefiable foundation sand. To characterizethe cyclic behaviour of the sand and to support the use of advanced constitutive models inthe design of the tunnel, key to simulate liquefaction realistically in such a complex project,five cyclic undrained torsional tests were executed. These tests, in which imposed strainincreases progressively until and during liquefaction, considering strain amplitude levelswith a limited number of cycles, allow a more thorough study of the phase after initialliquefaction than the usual test with constant stress amplitude and the necessary number ofcycles to attain liquefaction. Additionally, they provide high quality data, essential to calibrateadvanced constitutive models. From their analysis, it is concluded, as expected, thatthe number of cycles until initial liquefaction increases with relative density and confiningpressure. Moreover, while before initial liquefaction maximum excess pore pressure amplitudeis due to sand softening and consequent pore pressure build-up, after initial liquefactionit usually happens at the first cycle, being related to an initial higher dilation tendency,before particles loose contact. Finally, the damping ratio increases until a peak value, andthen, just before initial liquefaction, generally decreases till the end of the test.

This paper presents a study of the effect of a superabsorbent polymer (SAP) for autogenous shrinkage control on the uniaxial tensile behavior of steel fiber reinforced concrete (SFRC). The use of fibers and SAP potentially increases the durability of the concrete, preventing cracking by autogenous shrinkage and enhancing post-cracking behavior. Furthermore, SAP can provide further hydration for self-healing purposes and improve the ductility of the SFRC. In order to evaluate the effect of the addition of SAP in SFRC, dog-bone SFRC specimens with different dosages of superabsorbent polymers were cast and tested under uniaxial tension. The digital image correlation (DIC) technique was used to understand the effect of SAP on the steel fibers’ crack-bridging mechanisms. Surface strains and crack openings were inferred using the DIC technique. The effect of SAP and fibers on fresh and hardened concrete was individually investigated by flow tests and compressive strength tests. Autogenous shrinkage was measured in plain concrete to investigate the minimum SAP content required to mitigate autogenous shrinkage of 0.3%. The use of 0.3% SAP was also suffcient to reach multiple cracking behavior. This content of SAP completely suppressed the autogenous shrinkage with minimal side effects on compressive strength. An analytical formulation for the tensile behavior of SFRC was developed using the variable engagement model, presenting a mean correlation of R2 of 0.97 with the experimental results.

Tungsten is a critical raw material for European and U.S. economies. Tungsten mine residues, usually considered an environmental burden due to e.g. arsenic content, are also secondary tungsten resources. The electrodialytic (ED) process and deep eutectic solvents (DES) have been successfully and independently applied for the extraction of metals from different complex environmental matrices. In this study a proof of concept demonstrates that coupling DES in a two-compartment ED set-up enhances the removal and separation of arsenic and tungsten from Panasqueira mine secondary resources. Choline chloride with malonic acid (1:2), and choline chloride with oxalic acid (1:1) were the DES that in batch extracted the average maximum contents of arsenic (16%) and tungsten (9%) from the residues. However, when ED was operated at a current intensity of 100 mA for 4 days, the extraction yields increased 22% for arsenic and 11% for tungsten, comparing to the tests with no current. From the total arsenic and tungsten extracted, 82% and 77% respectively were successfully removed from the matrix compartment, as they electromigrated to the anolyte compartment, from where these elements can be further separated. This achievement potentiates circular economy, as the final treated residue could be incorporated in construction materials production, mitigating current environmental problems in both mining and construction sectors.

Estuarine flood risk management is a challenge for coastal managers since this type of system is usuallycomplex due to the presence of multiple trigger combinations that can induce flood events affecting differenttypes of human occupation. Furthermore, legal directives demanded countries to have flood risk assessmenttools therefore enhancing knowledge on estuarine triggers and flood damage typologies is useful for coastalmanagers. In this study three different flood events are compared and contrasted, each one having occurred in adifferent estuarine system chosen based on a set of criteria (temporal proximity, occurrence of human damagesand at least three flood triggers identified in each database). The diversity of data sources that characterizeseach database was examined, for the three events, which are described in terms of triggers and damages. Thecomparison highlighted that the local context was important in the estuarine flood combination of triggers anddisclosed two categories (one category comprising infrastructure economic and human damages; and anothercategory involving circulation interruption and functions disruption) of flood damages common between thestudied systems corresponding to different levels of relevance for management. The enhanced knowledgeacquired allowed the construction of a conceptual framework for damages that can contribute to more adequateestuarine flood risk frameworks.

Para caracterizar a agitação marítima no Porto de Leixões após o prolongamento do quebra-mar exterior, sob condições de alterações climáticas foi realizado um extenso grupo de ensaios em modelo físico tridimensional de agitação, num tanque do LNEC, à escala 1:80, representando-se toda a bacia portuária e o prolongamento do quebra-mar exterior do Porto de Leixões. Foram realizados ensaios com diferentes condições de agitação incidente para o rumo W e com dois níveis de maré, que correspondem ao nível médio e a preia-mar com uma sobrelevação representativa dos efeitos das alterações climáticas e da sua influência na agitação marítima. Foi medida a agitação em 30 pontos localizados na entrada do porto e no interior da bacia portuária e analisou-se o abrigo da bacia portuária com a ampliação do quebra-mar norte e as diferenças entre o abrigo para os dois níveis de maré ensaiados.As principais conclusões dos ensaios realizados foram que os maiores valores de alturas de onda ocorreram na zona exterior e de entrada do porto, diminuindo para o seu interior. Ao longo do canal de navegação, as alturas de onda vão diminuindo e no interior do porto obtiveram-se valores da altura de onda pequenos. A subida do nível do mar, para as condições ensaiadas, não afeta significativamente a agitação no interior da bacia portuária. No entanto, no exterior e zona de entrada do porto contribui para alterações da agitação que diferem consoante o período de pico e a altura de onda significativa incidente.

A modos de introdução, o artigo arranca com uma reflexão sobre o que se julga ser a essencial temática do

No artigo que se segue e depois de uma reflexão global e, de certa forma, introdutória, sobre o que se considera ser, ainda, a insuspeitada, mas grande importância da opção de se viver em afirmada relação com o exterior de uso público, aborda-se o que pode ser uma expressiva vitalização do espaço urbano pelas habitações térreas e com acessos diretos ao exterior e, também, a importância desta solução para uma forte e diversificada adequação da habitação a modos de vida e gostos habitacionais específicos, variados e mutantes. Passa-se, depois, para uma pequena reflexão sobre os cuidados de concepção específicos de habitações térreas e para a interessante e estimulante semelhança entre habitações térreas e moradias. Conclui-se o artigo com alguns desenvolvimentos, mais específicos, dedicados aos pátios e quintais privados, à variedade formal e funcional que carateriza toda a grande família de espaços exteriores privativos e, finalmente, ao que se julga ser o importante conjunto de vantagens que carateriza os exteriores privativos e bem relacionados com o nível térreo.

Este artigo foca a comparação da aplicação de carvão ativado em pó (PAC) nos tratamentos secundário e terciário para controlo de fármacos (PhC) em estações de tratamento de águas residuais (ETAR) urbanas. Foram realizados ensaios de adsorção à escala de laboratório, com um PAC selecionado, três PhC alvo, em licor misto e efluente secundário de uma ETAR. Através de modelação matemática, prevê-se que, para assegurar 80% de remoção do total dos três PhC, será necessária uma dose de PAC de 16 mg/L se utilizada a opção de tratamento secundário, ou de 7,5 mg/L se a opção for o tratamento terciário. A análise de custos aponta para custos anualizados, incluindo CAPEX e OPEX, de 0,05

This article presents an overview of the current European practices with regards to protecting surface water and groundwater bodies, in what concerns the application of legislation to protect water resources and to evaluate the vulnerability of water bodies to traffic related activities. This is achieved through the application of the EU Water Framework Directive and all Directives containing procedures to identify pressures affecting the state of water and environment, and the establishment of measures to ensure that all surface water and groundwater bodies achieve good status. A flowchart has been constructed to assist the assessment of the environmental legal constraints related to a road project. A combination of layers was integrated in GIS environment to address legislative needs and constraints, as well as the need to implement a risk assessment analysis of road runoff impact to surface and groundwater bodies.