Flexural and shear behaviour of precast sandwich slabs comprising thin walled steel fibre reinforced self-compacting concrete

Publicado em "Rheology and processing of construction materials", ISBN 978-2-35158-137-7Insulated sandwich panels are often composed of external concrete layers, mechanically connected through metallic elements, such as trusses. Due to their high thermal conductivity, metallic connectors tend to cause thermal bridges on the building envelope. In view of this problem, an innovative solution for sandwich slabs is proposed within the framework of a pre-fabricated modular housing system. The referred slabs are based on a sandwich solution composed by two thin layers of Steel Fibre Reinforced Self-Compacting Concrete (SFRSCC) that are connected by thin perforated plates of Glass Fibre Reinforced Polymer (GFRP), used together with a thermal insulation core-layer. The bottom concrete layer is reinforced with conventional steel rebars and steel fibres, whereas the upper one does not have conventional reinforcement. This paper presents a preliminary experimental program aiming to assess the flexural and shear behaviour of this type of sandwich panel solution. The obtained results confirm the feasibility of the proposed sandwich slab system, revealing its capacity in terms of load carrying capacity and ductility performance. In addition, the flexural behaviour of the tested specimens was numerically analysed for the serviceability limit states using the finite element method with consideration of the material non-linearity.Fundação para a Ciência e a Tecnologia (FCT

Integrated model for predicting the flexural capacity of concrete elements reinforced with non-corrodible discrete reinforcements

The present work describes an integrated approach that leads to the development of a new model capable of describing the tensile behavior (mode I) of fiber reinforced concrete (FRC), considering the orientation of the fibers, the fibers segregation along the cross-section of the FRC members and the pullout constitutive model of each fiber bridging the two faces of a crack. The possibility of the numerical model to capture the flexural behavior of nonmetallic fiber reinforced concrete members is explored by simulating the response of polypropylene fiber reinforced concrete notched beams submitted to 3-point bending tests.This work is supported by the European Regional Development Fund (FEDER) through the Competitiveness and Internationalization Operational Program – COMPETE under the NG_TPfib project POCI-01-0247-FEDER-033719

Development of sandwich panels for multi-functional strengthening of RC buildings: characterization of constituent materials and shear interaction of panel assemblies

This paper presents an experimental and numerical study aiming at the development of a sustainable and multifunctional composite sandwich panel for the rehabilitation of reinforced concrete (RC) buildings from the 1960s to the mid-1980s. The sandwich panel, which was designed for the structural, thermal and acoustic refurbishment of building facades, comprises three main components: (i) thin outer layers of Recycled Steel Fibre Reinforced micro–Concrete (RSFRC) that fulfil the strength, ductility and durability requirements of the panel; (ii) a lightweight core made of polystyrene that provides thermal insulation; and (iii) internally distributed glass fibre reinforced polymer (GFRP) connectors that join the different layers of the panel, providing an adequate structural behaviour to the composite system. The mechanical characterization tests highlighted the viability of using RSFRC for the production of structural sandwich facade panels, as relatively high post-cracking tensile capacity was obtained for thin RSFRC layers. Pushout and pullout tests were carried out on intermediate-scale specimens representative of the sandwich panel solution for assessing the overall composite behaviour of the sandwich panels and analysing the influence of the type of core insulation layer (expanded/extruded polystyrene cores, with different surface finishing), of the anchoring conditions (25 and 35 mm of embedment depth) and diameter of the GFRP connectors (8 and 12 mm). These tests showed that the structural GFRP connectors with diameters of 8 and 12 mm are able to ensure shear load transfer between RSFRC layers, exhibiting better composite behaviour when combined with anchorage depths of 25 and 35 mm, respectively. The numerical part of this study aimed at modelling the failure mechanisms observed at the interface between RSFRC and polystyrene, showing good agreement between experimental and numerical results, with important conclusions being drawn regarding cohesion and friction angle between these materials.The first author wishes to acknowledge the financial support provided by the Portuguese Foundation for Science and Technology (FCT) and the Eco-Construction and Rehabilitation (EcoCoRe) Doctoral Program through the research grant PD/BD/52657/2014. The second author acknowledges the support provided by the project ICoSyTec, POCI-01-0145-FEDER-027990, financed by the FCT (Portuguese Foundation for Science and Technology) and co-funded by FEDER through Operational Competitiveness and Internationalization Programme (POCI)

Creep behavior of RC slabs strengthened NSM CFRP laminate strips under different environmental conditions

With the aim of analyzing the long-term deformational performance of concrete elements flexurally strengthened with the near-surface mounted (NSM) technique, an experimental program has been launched using slab specimens submitted to sustained loads under the following environmental conditions: (i) 20ºC temperature and 55% relative humidity; (ii) immersed in water tank at 20ºC with 0% of chlorides; (iii) immersed in water tank at 20ºC with 2.5% of chlorides; (iv) submitted to wet/dry cycles at 20ºC with 2.5% of chlorides. The slabs are continuously monitored in terms of mid-span vertical deflection and strains (in concrete, CFRP laminate strip and steel reinforcements). The present paper summarizes the preliminary results obtained in this ongoing project

Creep behavior of concrete elements strengthened with NSM CFRP laminate strips under different environmental conditions

The present work intends to contribute for the knowledge on the long-term deformational performance of concrete structures strengthened with the near-surface mounted (NSM) technique. For that purpose a wide experimental program has been initiated using beam pullout and slab specimens submitted to sustained loads under the following environmental conditions: (i) 20ºC temperature and 55% relative humidity; (ii) immersed in water tank at 20ºC with 0% of chlorides; (iii) immersed in water tank at 20ºC with 2.5% of chlorides; (iv) submitted to wet/dry cycles at 20ºC with 2.5% of chlorides. The slabs are continuously monitored in terms of mid-span vertical deflection and strains (in concrete, CFRP laminate strip and steel reinforcements), whereas for the case of the beam pullout specimens monitoring includes the free and loaded end slips and strain in CFRP laminate strip. The present paper summarizes the preliminary results

Abordagem multi-física ao comportamento em serviço das estruturas de betão: monitorização dos campos intermos de humidade

No âmbito do projeto de investigação denominado SeLCo – “Comportamento em serviço de estruturas de betão: uma abordagem multi-física das tensões autoinduzidas” – está a ser realizado um conjunto de trabalhos conducentes ao estabelecimento de abordagens de simulação higro-mecânica para estudo do carácter não uniforme das tensões associadas à retração de secagem em estruturas de betão armado. De facto, a secagem do betão ocorre de forma progressiva da superfície para o interior, originando deformações impostas. Para que possam ser simuladas as tensões decorrentes destes processos é primeiramente necessário dispor de modelos capazes de simular os campos de humidade, devidamente fundamentados em resultados obtidos através de medições experimentais. O presente artigo dedica atenção ao último aspeto, apresentando um conjunto de trabalhos realizados com o intuito de melhor compreender os desafios envolvidos na monitorização da humidade interna no betão. Apesar de haver vários trabalhos na bibliografia relativamente a este assunto, são escassos os que comparam o desempenho de metodologias e sensores para medição da humidade interna no betão. Neste trabalho são apresentados vários conjuntos de experiências que comparam o desempenho de sensores e de procedimentos de monitorização, explanando-se as principais ilações e estratégias a adotar no contexto do programa experimental a conduzir no âmbito da investigação sobre tensões autoinduzidas no betão

Desenvolvimento de painel sanduíche multifuncional para reabilitação sustentável de edifícios porticados de betão armado: caracterização de componentes

Esta comunicação apresenta um trabalho de investigação dedicado ao desenvolvimento de um painel sanduíche compósito multifuncional concebido para a reabilitação estrutural e térmica de edifícios porticados de betão armado construídos em Portugal a partir da década de 1960 e até meados da década de 1980. Este painel é composto essencialmente por três componentes que visam assegurar a multifuncionalidade pretendida, nomeadamente: (i) finas camadas exteriores, de cariz estrutural, em microbetão reforçado com fibras de aço recicladas resultantes do processo de reciclagem de pneus (MBRFR); (ii) núcleo em poliestireno, para assegurar isolamento térmico contínuo ao painel; e (iii) conetores poliméricos reforçados com fibras de vidro (GFRP), para conferir uma adequada conexão entre as diferentes camadas. O presente artigo aborda primeiramente a caraterização mecânica efetuada ao MBRFR (comportamento em compressão e tração) e aos conetores GFRP (ensaios de tração direta), sendo ainda apresentados os testes efetuados para seleção do material de isolamento térmico a adotar na conceção do painel sanduíche em desenvolvimento. Estes testes abrangem a realização de ensaios de corte em elementos compósitos representativos do referido painel, nos quais se fez variar a tipologia de poliestireno adotada para a camada de isolamento, com o objetivo de avaliar a influência que esta camada pode ter nas condições de ligação dos constituintes do painel sanduíche. Os resultados obtidos permitiram tirar conclusões importantes acerca desta influência, revelando que o material e especialmente a superfície de acabamento podem contribuir de forma não-negligenciável para o comportamento estrutural da solução compósita.O primeiro autor deste trabalho agradece à Fundação para a Ciência e Tecnologia (FCT) o apoio financeiro concedido através da bolsa de doutoramento PD/BD/52657/2014, atribuída no âmbito do Programa Doutoral em Construção e Reabilitação Eco-eficientes (EcoCoRe). Agradece-se ainda à FCT o apoio financeiro prestado, nomeadamente no âmbito do projeto PTDC/ECM-EST/2635/2014, e toda a colaboração e apoio prestado pelas empresas Twincon, BVT-Rausch, PreConTech, Danosa/Eurofoam e IberFibran, através do fornecimento do material necessário para a realização da atividade experimental descrita neste artigo

Desenvolvimento de painel sanduíche multifuncional para a reabilitação sustentável de edifícios porticados de betão armado: caracterização de componentes

Esta comunicação apresenta um trabalho de investigação dedicado ao desenvolvimento de um painel sanduíche compósito multifuncional concebido para a reabilitação estrutural e térmica de edifícios porticados de betão armado construídos em Portugal a partir da década de 1960 e até meados da década de 1980. Este painel é composto essencialmente por três componentes que visam assegurar a multifuncionalidade pretendida, nomeadamente: (i) finas camadas exteriores, de cariz estrutural, em microbetão reforçado com fibras de aço recicladas resultantes do processo de reciclagem de pneus (MBRFR); (ii) núcleo em poliestireno, para assegurar isolamento térmico contínuo ao painel; e (iii) conetores poliméricos reforçados com fibras de vidro (GFRP), para conferir uma adequada conexão entre as diferentes camadas. O presente artigo aborda primeiramente a caraterização mecânica efetuada ao MBRFR (comportamento em compressão e tração) e aos conetores GFRP (ensaios de tração direta), sendo ainda apresentados os testes efetuados para seleção do material de isolamento térmico a adotar na conceção do painel sanduíche em desenvolvimento. Estes testes abrangem a realização de ensaios de corte em elementos compósitos representativos do referido painel, nos quais se fez variar a tipologia de poliestireno adotada para a camada de isolamento, com o objetivo de avaliar a influência que esta camada pode ter nas condições de ligação dos constituintes do painel sanduíche. Os resultados obtidos permitiram tirar conclusões importantes acerca desta influência, revelando que o material e especialmente a superfície de acabamento podem contribuir de forma não-negligenciável para o comportamento estrutural da solução compósitaFundação para a Ciência e Tecnologia (FCT) o apoio financeiro concedido através da bolsa de doutoramento PD/BD/52657/2014, atribuída no âmbito do Programa Doutoral em Construção e Reabilitação Eco-eficientes (EcoCoRe). Agradece-se ainda à FCT o apoio financeiro prestado, nomeadamente no âmbito do projeto PTDC/ECM-EST/2635/2014, e toda a colaboração e apoio prestado pelas empresas Twincon, BVT-Rausch, PreConTech, Danosa/Eurofoam e IberFibra

An investigation of the interactions between an E. coli bacterial quorum sensing biosensor and chitosan-based nanocapsules

We examined the interaction between chitosan-based nanocapsules (NC), with average hydrodynamic diameter ∼114–155 nm, polydispersity ∼0.127, and ζ-potential ∼+50 mV, and an E. coli bacterial quorum sensing reporter strain. Dynamic light scattering (DLS) and nanoparticle tracking analysis (NTA) allowed full characterization and assessment of the absolute concentration of NC per unit volume in suspension. By centrifugation, DLS, and NTA, we determined experimentally a “stoichiometric” ratio of ∼80 NC/bacterium. By SEM it was possible to image the aggregation between NC and bacteria. Moreover, we developed a custom in silico platform to simulate the behavior of particles with diameters of 150 nm and ζ-potential of +50 mV on the bacterial surface. We computed the detailed force interactions between NC-NC and NC-bacteria and found that a maximum number of 145 particles might interact at the bacterial surface. Additionally, we found that the “stoichiometric” ratio of NC and bacteria has a strong influence on the bacterial behavior and influences the quorum sensing response, particularly due to the aggregation driven by NC

The European Reference Genome Atlas: piloting a decentralised approach to equitable biodiversity genomics.

ABSTRACT: A global genome database of all of Earth’s species diversity could be a treasure trove of scientific discoveries. However, regardless of the major advances in genome sequencing technologies, only a tiny fraction of species have genomic information available. To contribute to a more complete planetary genomic database, scientists and institutions across the world have united under the Earth BioGenome Project (EBP), which plans to sequence and assemble high-quality reference genomes for all ∼1.5 million recognized eukaryotic species through a stepwise phased approach. As the initiative transitions into Phase II, where 150,000 species are to be sequenced in just four years, worldwide participation in the project will be fundamental to success. As the European node of the EBP, the European Reference Genome Atlas (ERGA) seeks to implement a new decentralised, accessible, equitable and inclusive model for producing high-quality reference genomes, which will inform EBP as it scales. To embark on this mission, ERGA launched a Pilot Project to establish a network across Europe to develop and test the first infrastructure of its kind for the coordinated and distributed reference genome production on 98 European eukaryotic species from sample providers across 33 European countries. Here we outline the process and challenges faced during the development of a pilot infrastructure for the production of reference genome resources, and explore the effectiveness of this approach in terms of high-quality reference genome production, considering also equity and inclusion. The outcomes and lessons learned during this pilot provide a solid foundation for ERGA while offering key learnings to other transnational and national genomic resource projects.info:eu-repo/semantics/publishedVersio