O uso de laminados de CFRP pré-esforçados no reforço de estruturas de betão armado

Este trabalho foi suportado por fundos FEDER através do Programa Operacional Fatores de Competitividade - COMPETE e fundos nacionais, através da FCT - Fundação Português de Ciência e Tecnologia no âmbito do projeto FRPreDur - PTDC/ECM-EST/2424/2012.info:eu-repo/semantics/publishedVersio

Bond between glulam and NSM CFRP laminates

With the aim of evaluating the bond behaviour between glulam and carbon fibre reinforced polymer laminates strips, an experimental program using pull-out tests was carried, when the near-surface strengthening technique is applied. Two main variables were studied: the bond length and the type of pull-out test configuration. The instrumentation included the loaded and free-end slips, as well as the pull-out force. Based on the obtained experimental results, and applying an analytical-numerical strategy, the local bond stress-slip relationship was determined. In this work the tests are described, the obtained results are presented and analysed, and the applicability of an inverse analysis to obtain the local bond law is demonstrated.This work is supported by FEDER funds through the Operational Programme for Competitiveness Factors - COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the project PTDC/ECM/74337/2006. The authors also like to thank all the companies that have been involved supporting and contributing for the development of this study, mainly: S&P Clever Reinforcement Iberica Lda., Portilame, MAPEI and Rothoblaas

Flexão simples : análise comparativa REBAP vs. EC2

O Eurocódigo 2 recomenda a utilização de relações tensões-extensões de cálculo quer para o betão quer para o aço, diferentes das propostas pelo REBAP. Com o objectivo de analisar a influência desta alteração normativa no dimensionamento à flexão simples de secções rectangulares, efectuou-se um estudo comparativo em termos de grandezas adimensionais. Na comunicação descreve-se o estudo efectuado, assim como, as principais conclusões obtidas

Modelação estrutural da ala norte do edifício neoclássico do Hospital Geral de Santo António

Presentemente a Ala Norte do edifício neoclássico do Hospital Geral de Santo António (HGSA) encontra-se em remodelação. Com o objectivo de avaliar o seu nível de segurança, procedeu-se à realização de modelações tridimensionais do objecto para as condições actuais de carregamento, em regime linear e não linear material com recurso ao programa de elementos finitos FEMIX. Neste trabalho é apresentada a sinopse dos estudos efectuados

Assessment of GFRP bond behaviour for the design of sustainable reinforced seawater concrete structures

Freshwater is an increasingly scarce resource. Its use in the production of concrete is one important contributor to its fast depletion. Alternatively, the use of seawater for reinforced concrete production, combined with the use of glass fibre reinforced polymers (GFRP) as reinforcement, may represent an interesting solution to increase concrete sustainability. The objective of this paper is to explore this promising solution through the development of concrete compositions with seawater. Additionally, it is also an objective to assess the bond behaviour between GFRP rods and concrete, in a design perspective. The influence of concrete age, rod diameter and anchorage length were also investigated. An analytical model capable of determining the local bond stress-slip laws was used. Results demonstrated that the use of seawater had no relevant effects on neither concrete mechanical properties nor bond behaviour.The study presented in this paper is a part of the research project “NEXT-SEA: Next Generation Monitoring of Coastal Systems in a Scenario of Global Change”, financed by CCDRN and FEDER funds in the scope of the Next-sea project (NORTE-01-0145-FEDER-000032). The authors acknowledge all the companies that have been involved supporting and contributing for the development of this study, mainly: S&P Clever Reinforcement Ibérica Lda., Burgoparaíso – Unipessoal Lda., Secil, Sika Portugal – Produtos Construção e Indústria S.A. The first and the last authors wishes also to acknowledge the grants SFRH/BD/131913/2017 and SFRH/BSAB/150266/2019, respectively, provided by FCT, financed by European Social Fund and by national funds through the FCT/MCTES

Fracture energy of steel fiber-reinforced concrete

Steel fiber-reinforced concrete (SFRC) is a cementitious material reinforced with discrete fibers. The energy absorption capacity is the main material property benefited by fiber reinforcement. Closed-loop servo-controlled equipment should be used to evaluate this property. The tests should be carried out using displacement control in order to obtain the postpeak force-displacement relationship (tensile strain-softening branch).To assess the fracture energy of SFRC, three-point bending tests were carried out using displacement control. Series of notched beams reinforced with 30, 60, and 90 kg/m(3) of hooked-end steel fibers were tested. Besides the energy dissipated in fracturing the concrete, the energy determined from the force-displacement relationship can also include the energy absorbed during nonlinear behavior of concrete in compression. Ductile materials, such as concrete reinforced with a high content of fibers, develop large deflections before exhausting their energy absorption capacity. In these cases, the "fixed" points of the bar supporting the displacement transducer may not remain fixed, adding an extra deflection into the control displacement transducer and thus leading to incorrect evaluation of the fracture energy. These factors are analyzed in the present work in order to assess the suitability of the specimen dimensions and the test procedures for evaluating the fracture energy of SFRC

Comportamento da ligação de laminados de CFRP inseridos no betão

Com o objectivo de avaliar a influência da classe do betão e do comprimento de ancoragem do laminado de fibras de carbono (CFRP), no comportamento da ligação, com adesivo epoxídico, entre laminado e betão, foram efectuadas campanhas de ensaios com três classes de betão e três comprimentos de amarração. No presente trabalho, os ensaios de arranque em flexão efectuados são descritos e os resultados obtidos são apresentados e analisados

Flexão composta : análise comparativa REBAP vs. EC2

No contexto actual nacional, o dimensionamento de estruturas de betão armado tem sido maioritariamente efectuado em conformidade com a norma nacional, o Regulamento de Estruturas de Betão Armado e Pré Esforçado (REBAP). Com a aprovação, no passado recente, do Eurocódigo 2 (EC2) a nível europeu, antevê-se que em breve lhe seja atribuído o estatuto de norma nacional, através da publicação de um texto idêntico. Em termos gerais o EC2, quando comparado com o REBAP, apresenta diferenças consideráveis na forma e no conteúdo que se repercutem no dimensionamento das estruturas de betão armado. Perante este cenário torna se imperioso efectuar estudos comparativos entre as duas normas aos mais diferentes níveis. O caso particular do dimensionamento à flexão ao nível da secção transversal em elementos estruturais lineares, que tem por base a hipótese de Navier Bernoulli (secções planas antes e após a deformação), recorre a leis tensões extensões de cálculo dos materiais intervenientes: o betão e o aço. As propostas do REBAP e do EC2 para definir estas leis são ligeiramente diferentes. Em trabalhos anteriores demonstrou se que as diferenças obtidas no dimensionamento de secções rectangulares à flexão simples adoptando as duas regulamentações (REBAP e EC2) são marginais. No presente trabalho pretende se avaliar a mesma diferença, mas desta feita para o caso em que o elemento estrutural se encontra sujeito a flexão composta. Deste modo, o objectivo é o de analisar a influência das diferenças que existem entre o REBAP e o EC2 ao nível dos diagramas tensões extensões de cálculo para os materiais betão e aço, no dimensionamento de secções rectangulares à flexão composta. No presente trabalho descreve se o estudo comparativo efectuado, assim como as principais conclusões obtidas

Caracterização experimental da ligação de laminados de CFRP inseridos no betão de recobrimento

Relatório 02 DEC/E-1

Bond between near-surface mounted CFRP laminates and the concrete in structural strengthening

Near Surface Mounted (NSM) Laminate Strips of Carbon Fiber Reinforced Polymer (LSCFRP) is a promising technique for increasing the flexural and shear strength of deficient reinforced concrete members. When compared to externally bonded reinforcing (EBR) technique, NSM LS-CFRP technique shows several advantages, namely: higher prevention to the peeling phenomenon; extra protection against fire, mechanical and environmental damaging effects; easier and faster installation. To evaluate the concrete/ LS-CFRP bond behavior, an experimental campaign of pullout-bending tests was carried out, where the influence of the concrete strength and the LS-CFRP bond length was considered. Taking the experimental results and using a numerical method developed for this purpose, an analytical bond stress-slip relationship was evaluated. The present paper describes the numerical strategy developed, its applicability to the tests carried out and its usefulness for predicting the anchorage length