The degradation mechanisms of bonded joints between CFRP laminates and steel substrates under severe environmental conditions require more durability data and studies to increase the database and better understand their causes. Studies on bond properties of double-strap CFRP-to-steel bonded joints with two different composite materials as well as adhesive coupons subjected to freeze-thaw cycles for 10,000 h were conducted to reduce that gap. In addition, the equivalent to the number of thermal cycles and their slips induced in the CFRP laminates was replicated by an equivalent (mechanical) loading-unloading history condition imposed by a static tensile machine. The mechanical properties of the adhesive coupons and the strength capacity of the bonded joints were only slightly changed by the artificial aging. It was confirmed that the interfacial bond strength between CFRP and adhesive is critically related to the maximum shear stress and failure mode. The interfacial bond strength between adhesive and steel degraded with the aging. However, the equivalent thermal cyclic bond stress caused no detectable damage on the bond because only the interfacial elastic regime was actually mobilized, which confirmed that pure thermal cycles aging, per se, at the level imposed, have a low impact on the degradation of CFRP-to-steel bonded joints.

The estimation of the long-term durability of adhesively bonded interfaces between Fiber Reinforced Polymers (FRP) and concrete substrates is crucial because degradation potentiates FRP premature debonding. One of the main reasons for mistrusting the use of FRP composites is the premature debonding phenomenon, which, associated to degradation, has been preventing their widespread use. In this research work, an analytical model is proposed that introduces ageing to estimate the effects of degradation of Glass (G) FRP externally bonded to concrete. Cycles were used to experimentally accelerate ageing of beam specimens, namely, (i) salt fog cycles; (ii) wet-dry cycles with salted water; (iii) temperature cycles between −10 °C and +30 °C; and (iv) temperature cycles between +7.5 °C and +47.5 °C. Based on the experimental results obtained and a corresponding bond-slip curve, the analytical model predicts the complete debonding process between FRP composites and a substrate. Consequently, the temporal evolution of the degradation of the bonded interfaces can be calculated and compared with the initial situation prior to exposure. The effects of the environmental conditions are reported and compared.

The aim of the present study was to proceed to a numerical analysis of the gravity load effects on the behaviour of reinforced concrete beam critical zones when subjected to cyclic loads. A parametric study to assess the influence of different levels of gravity load on RC beam critical zones subjected to cyclic loading was carried out. For this purpose, assuming the level of gravity load as a variable parameter, a nonlinear numerical model of a beam-column connection, previously calibrated with experimental data, was used. In order to evaluate the gravity load effects in the global response, a numerical study of a RC frame system is also presented. The numerical results are analysed in terms of global hysteretic response, accumulated energy dissipation and equivalent viscous damping ratio. In this numerical study, it was observed that the hysteretic response depends on the load path. In the presence of higher gravity load levels, the structure hysteretic behaviour exhibits higher damage levels, associated to a failure mechanism corresponding to the formation of four span plastic hinges. Thus, the proper test procedure should involve the imposition of a reverse cyclic displacement history starting each cycle from the gravity load effects.

Warm mix asphalt (WMA) is produced by a variety of technologies at lower temperatures that enable to gain important environmental and social benefits and, in consequence, to contribute to a more sustainable transportation infrastructure. The producer usually defines the temperatures used in WMA production. However, some references suggest the increase of temperature in order to allow a longer time to transport or to compact in cases of unfavourable weather conditions, mainly under low temperatures. The objective of this paper is to analyse the feasibility of producing WMA at the same temperatures of hot mix asphalt (HMA) guaranteeing an adequate compaction, and final performance in service. The paper describes a laboratory study to investigate the properties of a WMA using different additives and varying the mixing and compaction temperatures. The effect of production temperatures on the performance of the WMA was evaluated through binder drainage (production phase), volumetric properties (compaction phase), and resistance to permanent deformation (service phase). The paper also presents a numerical study on the time available for paving WMA under unfavourable climatic conditions. Results demonstrated that it is possible to produce WMA at high temperatures without problems of binder drainage, during transport, and of performance in service if adequate compaction is achieved. In fact, the production temperatures influenced the compaction phase. However, it is possible to increase the temperature without negatively affecting the required volumetric properties. The rut depth of the permanent deformation test was mostly influenced by the air-voids of the compacted WMA and the binder. From the numerical study, it was concluded that the time available for in situ compaction increased substantially when WMA was paved at higher temperature. However, in cases of low air temperature and thin layer, the increase of temperature may not be sufficient to obtain the desired level of density or air-voids.

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Ao longo da sua vida útil os edifícios históricos estão sujeitos a alterações de uso, a agentes ambientais e a diferentes ações como assentamentos do solo, incêndios, inundações ou sismos, para os quais podem não estar preparados. Além disso, a falta de manutenção contínua ajuda a colocar grande parte desse património em risco devido a problemas estruturais que reduzem sua própria segurança e a dos seus utilizadores. A preservação e mitigação de riscos do património cultural construído requer o uso de ferramentas confiáveis, a fim de avaliar o seu estado de conservação e identificar e prevenir potenciais vulnerabilidades. Os testes destrutivos tradicionais não são possíveis de realizar na maioria dos edifícios históricos, por isso é necessário selecionar testes não destrutivos (NDT) que permitam a caracterização física e mecânica dos materiais e do comportamento da estrutura. Neste artigo apresenta-se uma visão geral de diferentes equipamentos e testes NDT que permitem o levantamento geométrico e o mapeamento dos danos do edifício, a análise petrográfica da pedra de alvenaria, a caracterização das propriedades físicas e mecânicas dos materiais e o comportamento estrutural do edifício.

Os sistemas de reforço por colagem exterior têm sido alvo de várias abordagens, não só do ponto de vista do tipo de material a utilizar, como também sob o ponto de vista da técnica mais eficiente a seguir. As fibras reforçadas com polímeros (FRP) têm sido, no último par de décadas, alvo de investigação exaustiva, tendo-se verificado que esses sistemas nutrem de ductilidade algo reduzida devido ao descolamento prematuro do material de reforço da superfície de betão. Por conseguinte, o aço inox devidos às suas boas características anticorrosivas e ductilidade apresenta-se como uma alternativa viável aos compósitos de FRP. Assim, com vista a melhorar a ductilidade dos elementos estruturais reforçados, em vez de se recorrer a técnicas de reforço não tradicionais (e.g., Externally Bonded Reinforcement (EBR) ou Near Surface Mounted (NSM)) que estão sempre associadas a roturas prematuras por colagem do elemento de reforço quando a extensão nele instalada está muito aquém do seu valor de rotura, dever-se-á seguir outras técnicas de reforço por colagem. Com vista a interpretar e perceber o desempenho da ligação aço-inox, desenvolveu-se uma campanha experimental em que os ensaios visam em testar e comparar a técnica EBR com uma técnica inovadora e desenvolvida pelos autores (CREatE – Continuous Reinforcement Embedded at Ends) através da realização de ensaios de arrancamento de ligações aço inox/betão. Estes ensaios consistem em aplicar uma força à barra de aço inox segundo uma direção que permite induzir uma rotura da ligação consistente com o Modo II de fratura. A técnica de correlação de imagem digital (DIC) foi utilizada na monitorização de todos estes ensaios tendo-se desenvolvido ainda diferentes modelos, analíticos e numéricos com recurso a um programa de cálculo automático não linear, que permitiram simular os processos de descolamento da ligação aço inox/betão segundo as técnicas EBR e CREatE.

Os edifícios históricos como os palácios, castelos, igrejas e templos, são exemplos do património construído e constituem uma parte importante do nosso património cultural. Estas construções históricas incluem normalmente paredes de alvenaria maciça e pedra natural. A salvaguarda do património construído em pedra é de importância inquestionável, pelo que devem ser desenvolvidas e estudadas técnicas de intervenção adequadas em materiais e estruturas. Neste artigo, é apresentada uma metodologia de ensaios não destrutivos para avaliar a conservação de edifícios históricos de pedra e, com base nesta metodologia, é mostrado um caso de estudo na Igreja de São Leonardo, monumento português construído na Atouguia da Baleia no século XIII.

This 1st Report of the project CrowdWork21 presents a summary of the information collected about workers in digital platforms by country (German, Hungary, Portugal and Spain). Each national report describes first the scientific debates about workers of digital platforms. After, the reports present the information collected about the national public debates and identifies the angles normally covered by the media in relation to the organisation of digital workers. Lastly, the reports present initial conclusions about the information collected in each country.

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The cyclic shift graph of a monoid is the graph whose vertices are elements of the monoid and whose edges link elements that differ by a cyclic shift. This paper examines the cyclic shift graphs of `plactic-like' monoids, whose elements can be viewed as combinatorial objects of some type: aside from the plactic monoid itself (the monoid of Young tableaux), examples include the hypoplactic monoid (quasi-ribbon tableaux), the sylvester monoid (binary search trees), the stalactic monoid (stalactic tableaux), the taiga monoid (binary search trees with multiplicities), and the Baxter monoid (pairs of twin binary search trees). It was already known that for many of these monoids, connected components of the cyclic shift graph consist of elements that have the same
evaluation (that is, contain the same number of each generating symbol). This paper focusses on the maximum diameter of a connected component of the cyclic shift graph of these monoids in the rank-$n$ case. For the hypoplactic monoid, this is $n-1$; for the sylvester and taiga monoids, at least $n-1$ and at most $n$; for the stalactic monoid, $3$ (except for ranks $1$ and $2$, when it is respectively $0$ and $1$); for the plactic monoid, at least $n-1$ and at most $2n-3$. The current state of knowledge, including new and previously-known results, is summarized in a table.

This paper makes a combinatorial study of the two monoids and the two types of tableaux that arise from the two possible generalizations of the Patience Sorting algorithm from permutations (or standard words) to words. For both types of tableaux, we present Robinson--Schensted--Knuth-type correspondences (that is, bijective correspondences between word arrays and certain pairs of semistandard tableaux of the same shape), generalizing two known correspondences: a bijective correspondence between standard words and certain pairs of standard tableaux, and an injective correspondence between words and pairs of tableaux.

We also exhibit formulas to count both the number of each type of tableaux with given evaluations (that is, containing a given number of each symbol). Observing that for any natural number $n$, the $n$-th Bell number is given by the number of standard tableaux containing $n$ symbols, we restrict the previous formulas to standard words and extract a formula for the Bell numbers. Finally, we present a `hook length formula' that gives the number of standard tableaux of a given shape and deduce some consequences.

This paper constructs presentations via finite complete rewriting systems for plactic monoids of types $A_n$, $B_n$, $C_n$, $D_n$, and $G_2$, using a unified proof strategy that depends on Kashiwara's crystal bases and analogies of Young tableaux, and on Lecouvey's presentations for these monoids. As corollaries, we deduce that plactic monoids of these types have finite derivation type and satisfy the homological finiteness properties left and right $\mathrm{FP}_\infty$. These rewriting systems are then applied to show that plactic monoids of these types are biautomatic.