Artigos de Revista

Reducing the cement content of concrete is of paramount importance towards sustainability, since its production process is highly energy-consuming and delivers massive CO2 emissions to the atmosphere. In this paper, the bond behaviour between steel and stainless-steel reinforcing bars and Low Binder Concrete (LBC), produced with approximately one half and almost one fourth of the minimum cement content prescribed in the standards, is experimentally investigated. Results show the compactness of the mixture to be the main parameter controlling bond development, more than the mixture compressive strength as suggested in published results and standards. A more compact and denser mixture increases the contact surface between the reinforcing bars and concrete, improving friction between both. LBC mixtures with lowered cement content, up to almost one fourth of the minimum recommended, can be used without jeopardizing the bond strength of reinforcing bars. LBC mixtures promise to be a fitting approach towards greater sustainability in the concrete production sector.

Partial safety factors present in codes are defined for the design of broad populations of structures. As a consequence, they do not always reflect correctly the uncertainties for specific existing structures. The possibility of adjusting them has therefore great interest when assessing an existing structure. The concept of design point connected to FORM offers a simple method to calibrate partial safety factors for individualvariables. This paper discusses the overall methodology and develops a set of analytical expressions for the probabilistic models more common in structural reliability.As it will be seen the partial factor for a particular variable can be adjusted once defined: (1) probabilistic model used to describe the uncertainty in that variable; (2) coefficient of variation of the variable; (3) fractileimplicit on the characteristic value used to quantify the design value; (4) importance of the variable in the limit state under consideration (measured by the respective sensitivity factor), and (5) target reliabilityindex.The choice of the probabilistic model influences significantly the partial factors and this influence rises as the coefficient of variation increases. As a consequence, more attention must be paid when choosing a probabilistic model for a variable with high coefficient of variation.

O artigo inicia-se com uma reflexão sobre o que se julga ser o atual interesse de uma adequada inovação no desenvolvimento das garagens comuns habitacionais. Sequencialmente apresentam-se alguns exemplos de caminhos para a humanização e residencialização das garagens comuns, discutem-se alguns hábitos e problemas considerados mais correntes neste tipo de espaços, e conclui-se o artigo com uma abordagem de atuais tendências formais e funcionais em garagens comuns habitacionais.

The characterization of the dynamic behavior of an arch dam, and its evolutionthroughout the structure's lifetime, provides important data for the safetycontrol process. Forced vibration tests remain a reliable technique for this purpose.The Baixo Sabor dam is a 123 m high arch dam recently built in Portugal.Forced vibration tests were performed before and after the reservoir filling.Two techniques for forced vibration test are compared, discrete frequencyscanning, the standard methodology, and continuous frequency scanning (sinesweep), a new proposed methodology, which allowed faster results withoutloss of precision. For the interpretation of test results two numerical models ofthe dam-reservoir-foundation system were built, and calibrated with the experimentaldata. A good match of numerical and experimental results wasobtained for the six lowest frequencies and corresponding mode shapes.

Among biological agents, insect attacks may cause severe degradation of timber structuresin the service life of buildings which leads to lower mechanical performance and, thus, maintenanceproblems over time. Additionally, compression perpendicular to the grain always features a weak spotwith respect to the long-term mechanical performance of timber members and joints. In the presentwork, the respective strength and elastic modulus were thus investigated for insect deterioratedwood. Following a standardized geometry, small samples degraded by anobiids were extractedfrom beams made of sweet chestnut wood (Castanea sativa Mill.) that were removed from service.Visual assessment of the external wood surfaces was then performed to identify areas infested byinsects. Afterwards, destructive monotonic compression tests were carried out perpendicularly tothe grain on the damaged area to determine the loss of compressive strength and elastic modulus.The experimental results showed that the loss of compressive strength and elastic modulus mightbe linearly correlated to the wood density loss for small samples infested by insects. Nonetheless,future work should focus on determining accurately the density loss in the insect-deteriorated partthrough non- or semi-destructive tests, in order to establish stronger relationships with the mechanicalproperties loss investigated.

To upgrade the response capability to coastal flood events, hazard predictions need to be improved throughintegrating the effect of the coastal morphological variability in the nearshore-foreshore-backshorehydromorphological processes induced by waves-tide-wind-atmospheric pressure. In order to evaluate the short-termmorphological response of different coastal typologies to potential flood conditions (spring high tide level, stormsurge, high wave height), field data acquired in 2019 in three sites in the West coast of Portugal with past floodingepisodes are presented and discussed. The preliminary results point out that under the same forcing conditions theshort-term response of the cross-shore beach profile that controls the flooding levels is dependent on the beachtypology, namely: the nature of the lower and upper limits of the beach face, profile gradient and its alongshorecontext. This knowledge can be used to develop robust and validated flood prediction tools contributing to improvemitigation and adaptation management strategies.

O presente artigo tem como objectivo apresentar custos de reabilitação de reservatórios apoiados incluindo custos unitários de intervenções de renovação não estrutural e funções de custo de construção civil e de equipamento electromecânico e instalações eléctricas. A metodologia para obter os custos de intervenções de reabilitação foi adaptada de trabalhos anteriores e e constituída por quatro etapas: 1) recolha, análise e processamento de dados; 2) actualização de custos a data de referência; 3) estabelecimento das rubricas de custo e identificação dos parâmetros característicos; 4) cálculo e validação dos custos de reabilitação. Os dados utilizados relativos a custos de reabilitação e a características das infra-estruturas são provenientes de mapas orçamentais de obras recentes efectuadas por várias entidades gestoras em Portugal. Descrevem-se as principais intervenções de reabilitação efectuadas em reservatórios em Portugal, incluindo a identificação dos parâmetros característicos. As funções de custo de reabilitação obtidas são comparadas com as funções de custo de construção de Reservatórios. Verifica-se que o custo de reabilitação de construção civil varia entre 5 % e 50 % do custo de construção e que o custo de reabilitação de equipamento electromecânico e instalações eléctricas varia entre 10 % e 200 % do custo de construção.

Métodos simplificados são alternativas úteis para análise prévia dos efeitos da ruptura de barragens, podendo orientar a tomada de decisão da realização de estudos mais completos. Nesse contexto, propõe-se uma nova abordagem simplificada para análise de aspectos da ruptura de barragens de terra, cuja falha ocorre por galgamento, a partir da altura da barragem e do volume do reservatório como dados de entrada. Casos hipotéticos de ruptura foram analisados por meio de simulações hidrodinâmicas, cujos resultados permitiramdesenvolver equações capazes de estimar o amortecimento da vazão de pico e o tempo de chegada da vazão máxima no vale a jusante. A abordagem proposta foi aplicada em estudo de caso hipotético (em uma barragem com 15 m de altura e 17 hm3 de volume no reservatório), obtendo-se resultados próximos dos alcançados por meio de outros metodos, especialmente na estimativa da vazão máxima no vale a jusante, onde as diferenças médias entre os resultados dos métodos considerados foram da ordem de 15%.

O artigo centra-se na temática da importância e do interessante protagonismo que pode ter o exterior privado, numa perspetiva de construção de uma

The success of experimental studies to investigate hydraulics of dam breaching requires an adequate specification of geotechnical parameters and control over its realization in field or in laboratory conditions. Although this is known, there are few studies specifically addressed to formulate and discuss the requirements for comparable laboratory hydraulic tests to study embankment failure by overtopping. This study addresses this research gap specifically for homogeneous earthfill dams. It is aimed at proposing and discussing a set of core procedures and monitoring techniques to be observed in studies of dam breaching by overtopping. A first procedural step involves the theoretical discussion of similarities between model and prototype erodibility. Further steps involve observations of breached model dams under controlled hydraulic and geotechnical conditions. Requirements for comparability of hydraulic laboratory practice are described and discussed, and it is argued that the key geotechnical parameters of control are the soil composition (more specifically, the fraction of fine material) and the compaction conditions (relative compaction and water content). To attain similarity conditions in what concerns model dam erodibility, whose failure modes should include headcuts and undercutting, a range of reference values for the geotechnical control parameters is suggested and construction/compaction methods are discussed.