Artigos de Revista

Several cases of alkali-silica reaction involving granitic aggregates have been diagnosed in damaged concrete structures in Portugal. Nonetheless, this kind of rock is usually regarded as slow/late reactive or even non-reactive to alkalis. Granitic rocks are widely exploited in Northern and Central Portugal, representing almost half of the produced aggregates in this country. Project IMPROVE rose from the need to accurately diagnose the potential reactivity of granites to alkalis. The study involved about forty granites collected from different regions in Portugal, from which the results of eight samples are being presented in this paper. The tests carried out include the petrographic analyses of the aggregates and mortar and concrete expansion tests. It was concluded that the content of microcrystalline quartz correlates better with the results of AAR-4.1 than with the other expansion tests.

Using waste as a civil engineering construction material represents an important environmental and economic advantage. In this context, it was studied the durability and permeability of a crushed concrete recycled aggregate (CCCDW), processed from construction and demolition waste (CDW), and an inert steel aggregate for construction (ISAC), processed from electric arc furnace (EAF) steel slag, with the aim to evaluate the technical feasibility of their recycling in the drainage layers of transport infrastructures. The durability of recycled materials was studied using the slake-durability test (SDT) proposed by International Society for Rock Mechanics (ISRM). In order to test the behaviour of the material in mechanical conditions more adverse than those specified in the ISRM method, more 600 rotation cycles than those foreseen in the original method were applied. As a complement to SDT tests, macro- and micropetrographic observations as well as physical characterizations of two recycledmaterials, both before and after SDT tests, were performed. Regarding the hydraulic behaviour of the recycled materials, constant-head permeability tests were carried out on specimens prepared from grain-size fractions in the ranges 0.25-2.0 mm and 2.0-20.0 mm. In the study was compared the behaviour of two recycled materials with two reference natural materials, a basalt and a limestone. The results obtained show, for the conditions tested, the technical feasibility of their recycling in the mentioned applications.

The role of environmental forcings on the fecal contamination dynamics in small coastal streams was investigated, using the Aljezur coastal stream (Portugal) as a test case. An integrated modeling approach, combining hydrological and coupled hydrodynamic-fecal indicator bacteria models, was applied to selected scenarios of relevant forcings, on the basis of previously calibrated and validated model applications. The forcings investigated included: tides, winds, waves, atmospheric pressure, bathymetry, river flow, and upstream fecal bacteria concentrations; this study targeted the characterization of the relative importance of these factors on the fecal contamination dynamics, to enhance our understanding of small coastal streams water quality dynamics. Results highlight distinct patterns for dry and wet periods. Fecal bacteria transport is mainly forced by tidal propagation, in dry periods; and by freshwater flows, during wet periods. The analysis reveals a complex hydraulic and water quality dynamic resulting from the interactions between the environmental forcings and strongly dependent on their relative strength. This analysis can be extrapolated for systems with a similar balance between the environmental factors.Read More: http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29EE.1943-7870.0001075

Smoke flow inside buildings is a major cause of death in the event of fire. Presently, fire or smoke doors areused, together with smoke control systems, to avoid smoke flowing beyond the boundaries of the firecompartment. In this research, it is proposed the use of downward air curtains to stop smoke flow, whichwill not impair visibility in escape routes. The methodology followed in this research includes: (i) thedevelopment of an analytical model that relates the relevant characteristic quantities of a plane jet with thecharacteristics of the environment in which the fire develops, (ii) small scale experiments with saltwatermodelling to assess the convective parameters that control the smoke tightness of the curtain, (iii) CFDsimulations to assess the performance of a full scale air curtain near a fire source and (iv) fire experiments with afull-scale test specimen. In this paper both the analytical model and the saltwater experiments are presented.Test results confirm that vertical downward air curtains are able to avoid smoke flow through openings andshow a good agreement with the theoretical model for predicting the minimum exhaust rate from the firecompartment. It has been shown that the exhaust flow rate depends on the air curtain flow rate and on the fluidheat expansion due to fire. Test results also make it possible to assess the minimum nozzle velocity to avoidsmoke leakage.

Much research in recent years has focused on the seismic analysis of concrete and earthfill dams,and few works have addressed the case of masonry dams. The structural behavior of masonrydams is controlled essentially by its discontinuous nature, which may induce significant nonlinearresponse during an intense earthquake. In this article, a numerical tool based on the Discrete ElementMethod is presented, aimed at the static, dynamic, and hydromechanical analysis of masonry gravitydams. The use of discontinuous models is mandatory for the study of failure mechanisms involvingthe masonry discontinuities, the dam-rock interface or the rock mass joints. The Discrete ElementMethod is able to assemble continuous and discontinuous meshes simultaneously in the same model,providing a versatile tool to consider various assumptions and levels of analysis, ranging from simplifiedto detailed structural representations. A comprehensive study of the seismic behavior of LagoaComprida Dam, located in Portugal, is presented. Both continuous and discontinuous models weredeveloped to assess the main failure mechanisms, including overstress, partial and global sliding,and overturning.

Wastewater services are fundamental for the protection of public health and environment, population wellbeing and sustainable development of communities. The value of urban water assets represents a major part of all public infrastructures. These assets must be managed rationally and efficiently, justifying investment priorities in a clear and straightforward way. Effective decision-making requires a comprehensive approach allowing the incorporation of desired performance at acceptable risk levels, considering investment and operational costs. Advanced sewer infrastructure asset management (IAM) is key to achieve and ensure adequate future levels of service, in issues such as flooding of urban areas, pollution prevention, balancing performance, risk and cost. The paper illustrates the integration of different support tools and methods by implementation of the AWARE-P procedure for planning IAM, demonstrated by the experience of fourteen wastewater utilities.

Several factors influence the behaviour of infilled frames, which have been a subject of research in the past with moderate success. The new generation of European design standards imposes the need to prevent brittle collapse of the infills and makes the structural engineer accountable for this requirement, yet it fails to provide sufficient information for masonry infills design. Therefore, the present work aims at understanding the seismic behaviour of masonry infill walls within reinforced concrete frames, using both unreinforced and reinforced solutions (bed joint reinforcement and reinforced plaster). For this purpose, three reinforced concrete buildings with different infill solutions were constructed at a scale of 1:1.5, all with the same geometry, and were tested on the shaking table of the National Laboratory for Civil Engineering, Portugal. All solutions performed adequately for the design earthquake, with no visible damage. Still, the experimental tests show that the double-leaf-unreinforced infill walls underperformed during a large earthquake, collapsing out of plane by rotating as rigid bodies with multiple configurations. Also the reinforced concrete buildings collapsed, because of the adverse interaction with the infill walls. The infill walls with bed joint reinforcement and reinforced plaster did not collapse out of plane, because of their connection to the concrete frame, which is an essential requirement.

A ventilação natural é uma eficiente estratégia projetual para ocondicionamento térmico passivo de edificações, ocorrendo por açãodos ventos, efeito chaminé ou pela combinação de ambos. Dentre asestratégias de ventilação, destacam-se os sheds, aberturas no telhado,que funcionam como captadores ou extratores de ar, dependendo de sualocalização em relação aos ventos dominantes. O objetivo desse artigo é avaliar ainfluência da variação na geometria dos sheds e na dimensão das aberturas deentrada e saída de ar no desempenho da ventilação natural. O sistema foi avaliadopara os ângulos de incidência dos ventos externos de 0° e 45° (extração) e 135° e180° (captação). A metodologia adotada foi a simulação por Dinâmica dos FluídosComputacional (CFD), utilizando como ferramenta o software CFX. Foramrealizadas análises quantitativas (taxas de renovação de ar/hora e coeficiente depressão nas aberturas) e qualitativas (planos de contorno e vetores de direção eintensidade do fluxo de ar). Os resultados indicam que sheds com geometriasaerodinâmicas e o aumento das aberturas de saída de ar incrementam o fluxo de arinterno. Para os sheds captadores o aumento isolado das aberturas de entrada de arnão proporciona uma melhora significativa na captação dos ventos pela cobertura.

Self-compacting concrete (SCC) is a concrete type that does not require vibration for placing and compacting. SCC possesses special technical features and properties that recommend its application in many jobs. Nevertheless, in some situations, it has been observed an inadequate behavior of the material at early ages due to shrinkage. The existing shrinkage prediction models were developed for standard concrete. In this paper three SCC mixtures, with different compressive strength, are studied in terms of autogenous and total shrinkage. The results are compared with the Eurocode 2 model. For the studied mixtures it was found that this model underestimates the autogenous shrinkage, while the total shrinkage is generally overestimated.