Research on the variability of the properties of recycled aggregate concrete is lacking and is necessary for the development of reliability analyses and code calibration procedures. This paper presents an experimental programme on the within-batch variability of the compressive strength, Young’s modulus, and splitting tensile strength of several recycled and natural aggregate concrete mixes. The influence of the recycled concrete aggregates on the mechanical properties and variability of concrete is analysed and discussed and benchmarks with standard predictions for the variability of natural aggregate concrete are made. It was found that full recycled aggregate concrete incorporation did not increase the variability of any of the properties tested, but intermediate ratios of recycled aggregate incorporation did. The properties of high-strength concrete mixes were more variable than that of all other mixes, irrespective of recycled aggregate incorporation. All properties of all compositions were suitably modelled by normal distributions. The coarse recycled aggregates were sourced from concrete waste.

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.

This preliminary report presents the outcomes of desk research, which was oriented to obtain a clear picture of the ‘state of the art’ in the involved countries and sectors. The report first reviews the main concepts and categories used to approach the topic and provides a definition of virtual work. Second, it describes the incidence and features of virtual work based on both European and national surveys. Third, it reviews previous research outcomes on the effects of virtual work on working conditions at national and sectoral level. Fourth, it analyses national approach to regulate virtual work. Fifth, the report addresses main institutional features of industrial relations in the three sectors and five countries; and the role played by social dialogue and collective bargaining at sectoral and company level to regulate working conditions of virtual workers.

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.