Reliability analysis of shear strengthening EBR FRP models

This work presents a statistically oriented study aiming to assess the reliability of some of the most well known design models available for the prediction of the contribution of fiber reinforced polymer (FRP) systems applied according to the externally bonded reinforcing (EBR) technique for the shear strengthening of reinforced concrete (RC) beams. Relevant data was collected from experimental programs carried out in recent years in the context of the shear strengthening with FRP, and an extended database was obtained. Using this data, the performance of fib, ACI, Italian and Australian design guidelines was appraised by means of comparing the contribution of the FRP shear systems predicted by the analytical formulations with those registered experimentally. In general, the obtained results were not very promising, since a large scatter of the design safety factor was observed and, for some cases, the contribution of the FRP systems predicted by the design models was highly unconservative, which may be a serious concern as these formulations may be currently being used in design practice.The study reported in this paper forms a part of the research programme Cutinemo, supported by FCT, PTDC/ECM/73099/2006

Desempenho de modelos analíticos de previsão da contribuição de materiais compósitos no reforço ao corte de vigas de betão armado

Na presente comunicação são apresentados alguns modelos analíticos para previsão da contribuição de materiais compósitos no reforço ao corte de vigas de betão armado recentemente introduzidos nos códigos de dimensionamento, sendo o seu desempenho aferido por comparação entre os valores estimados pelas formulações analíticas com os registados numa base de dados contendo informação referente a mais de 200 programas experimentais.Os autores manifestam os seus agradecimentos ao apoio prestado pela Fundação para a Ciência e Tecnologia (FCT) no projecto POCI/ECM/59033/2004. O primeiro autor agradece a bolsa UMINHO/POCI-59033/BI/05 concedida ao abrigo deste projecto

Novas perspectivas para o desenvolvimento de modelos de dimensionamento ao corte de vigas de betão armado reforçadas com FRP colado externamente

Com o presente artigo pretende-se apresentar uma base de dados (BD) contendo os registos relativos a mais de 250 vigas reforçadas ao corte com materiais poliméricos reforçados com fibras (FRP) e ensaiadas em diversos programas experimentais conduzidos por diferentes autores. O desempenho dos modelos de dimensionamento propostos pelo fib, ACI, e pelas Norma Italiana CNR-DT200 e Norma Australiana CIDAR é aferido comparando o comportamento observado experimentalmente com as previsões obtidas por via analítica. Tendo por base os resultados registados na BD, foi efectuado um estudo paramétrico com o objectivo de avaliar a influência no desempenho dos modelos de dimensionamento de diversos factores não explicitamente considerados nas formulações analíticas que os suportam. Os resultados são analisados, interpretados e apontadas as limitações encontradas nos modelos de dimensionamento em estud

Design models for shear strengthening of reinforced concrete beams with externally bonded FRP composites : a statistical vs reliability approach

Fundação para a Ciência e a Tecnologia (FCT) - POCTI/ECM/59033/200

Development of a proposed single-phase series active power filter without external power sources

The quality of electric power is receiving more and more attention from part of consumers, Distribution System Operators (DSO), Transmission System Operators (TSO) and other competent entities related to the electrical power system. Once the electrical Power Quality (PQ) problems have direct implications for business productivity, causing high economic losses, it is mandatory to develop solutions that mitigate these problems. Active Power Filters (APFs) are power electronic equipment capable of compensating PQ problems that have the ability to dynamically adjust their modes of operation in response to changes in load or in the power system. Among these solutions, the Series Active Power Filter (SeAPF) is specially conceived to deal with problems related to the power system voltage amplitude and waveform. Despite the ability to compensate voltage sags, voltage swells, voltage harmonics, and voltage imbalances in three-phase systems, the SeAPF has not achieved much success neither has not been widely adopted. The lack of interest in this equipment can be largely justified by its high cost and also because of some limitations presented by the SeAPF conventional topology. In this paper is presented a novel topology, as well as the control algorithms of a single-phase SeAPF that is connected directly to the power grid without the use of coupling transformers and that does not require the use of external power sources. The topology and control algorithms of the SeAPF proposed in this paper were firstly evaluated by means of simulation results obtained with PSIM software and, once validated, a laboratory prototype was developed, being presented experimental results that support the correct operation of the proposed system.This work has been supported by FCT – Fundação para a Ciência e Tecnologia within the Project Scope: UID/CEC/00319/2019. This work is financed by the ERDF – COMPETE 2020 Programme, and by FCT within project SAICTPAC/0004/2015-POCI-01-0145-FEDER-016434 and by FCT within project PTDC/EEI-EEE/28813/2017. Mr. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018 granted by the Portuguese FCT agency

Analytical and numerical analysis of the behaviour of RC beams flexural strengthened with CFRP

Experimental research regarding the flexural strengthening of reinforced concrete (RC) structures with Carbon Fibre Reinforced (CFRP) systems using the Externally Bonded Reinforcing (EBR) and the Near Surface Mounted (NSM) techniques has been carried out at the University of Minho. Considering the experimental results of this research, the performance of the ACI and fib formulations for the EBR flexural strengthening was appraised in this paper. The same was done in terms of NSM technique adopting for the CFRP debonding strain a value that is 70% of the CFRP ultimate strain, according to the recommendations of the ACI Committee 440. However, the experimental results show that the CFRP debonding strain is dependent on the CFRP percentage and existing longitudinal steel reinforcement ratio. To estimate an equation for the prediction of the CFRP debonding strain, which takes into account these parameters, a numerical model was applied to the simulation of the tests carried out.(undefined

Study on the technological and economic viability of introducing energy storage systems with solar photovoltaic panels

Solar photovoltaic represent one of the most promising technologies for generating electrical energy from renewable sources. In fact, as a result of the technological advances in the field of microelectronics and power electronics, photovoltaic systems have reached historic lows in terms of costs, surpassing the other types of renewable energy sources. The potential of the solar photovoltaic systems is enormous, being capable of meeting the energy needs of today, without compromising future needs, and allowing a sustainable development. With this in mind, several incentives and, consequently, legislations have been implemented around the world. In the Portuguese case, depending on the type of contract, for photovoltaic solar installations with value of power up to 1500 Wp the production surplus is injected into the power grid without any financial compensation. Considering the high investment, particularly regarding the photovoltaic panels, the support structure and the power electronics converters, it could be interesting to implement a system capable of storing the surplus energy for later use by the owner of the photovoltaic installation. This paper presents a study on the viability of energy storage systems in photovoltaic installations up to 1500 Wp. For this study, different consumer profiles, types of installations and geographic locations were considered, in order to perceive the technological and economic viability of this solution.This work has been supported by FCT -Fundancao para a Ciencia e Tecnologia within the Project Scope: UID/CEC/00319/2019. This work is financed by the ERDF COMPETE 2020 Programme, and FCT within project SAICTPAC/0004/2015-POCI-01-0145-FEDER-016434 and FCT within project PTDC/EEI-EEE/28813/2017. Mr. Luis A. M. Barros is supported by the doctoral scholarship PD/BD/143006/2018 granted by the Portuguese FCT agency

Improving the antioxidant activity of medicinal and aromatic plants by applying electron beam irradiation

Irradiation techniques have been applied for decontamination of aromatic and medicinal herbs. Their popularity in the pharmaceutical and food industry requires specific criteria in terms of microbiological safety [1, 2]. In this study the objective was to evaluate the effects of different doses of electron beam (EB) irradiation (0 kGy – control, 1 kGy and 10 kGy) on the antioxidant activity of Aloysia citrodora P., Melissa officinalis L., Melittis melissophyllum L. and Mentha piperita L.. The antioxidant properties of their infusions and methanolic extracts were evaluated through free radicals scavenging activity, reducing power and inhibition of lipid peroxidation in brain homogenates (TBARS assay). By comparing the results obtained from control and irradiated samples, it was evident that EB induced an increase in the ability to scavenge DPPH radicals and in the reducing power, independently of plant species and extract type. Nevertheless, a similar conclusion could not be performed for TBARS assay. In this case, the infusions from EB irradiated samples have also showed a higher effectiveness as lipid peroxidation inhibitors; however, some of the methanolic extracts (particularly those obtained from A. citrodora and M. piperita) did not allow an activity as high as the one observed in control samples. Even so, an increase in TBARS formation inhibition was also achieved in the methanolic extracts of M. melissophyllum and M. officinalis (this latter, only when a 10 kGy dose was applied). According to the described effects, it might be concluded that the application of EB irradiation is an effective way of increasing the antioxidant activity of the methanolic and aqueous extracts prepared from the assayed aromatic and medicinal plants.The authors are grateful to project PRODER nº 53514, AROMAP, for financial support of the work and E. Pereira grant, and to Fundação para a Ciência e a Tecnologia (FCT, Portugal) for financial support to CIMO (strategic project PEst-OE/AGR/UI0690/2014), J.C.M. Barreira grant (BPD/72802/2010) and L. Barros “Compromisso para a Ciência 2008” contract. The authors are also grateful to “MaisErvas - Aromáticas e Medicinais” for samples providing and to Dr. A. Rafalski, for e-beam irradiations and Prof. A. Chmielewski, General Director of the Institute of Nuclear Chemistry and Technology, Warsaw, Poland, for allowing e-beam irradiations

Irradiação com feixe de eletrões como um método de preservação da composição química de plantas aromáticas e medicinais

Introdução: Desde os tempos mais antigos que as plantas aromáticas e medicinais têm sido utilizadas não só como alimento, mas também para aplicações terapêuticas. Essas plantas têm propriedades medicinais com grande potencial de utilização no tratamento de diversas doenças, uma vez que são uma fonte natural de compostos bioativos. A irradiação com feixe de etetrões é utilizada para vários fins, destacando-se como uma técnica de descontaminação mas também de preservação das matrizes onde é aplicada. Objetivos: Neste trabalho foram avaliados os efeitos de diferentes doses de irradiação com feixe de eletrões (O kGy - controlo, 1 kGy e 10 kGy) na composição química e nutricional de Aloysia citrodora P. (limonete), Melissa officinalis L. (cidreira), Melittis melissophyllum L. (bretónica) e Mentha piperita L. (hortelã-pimenta). Materiais e Métodos: O valor nutricional foi determinado através de metodologias oficiais de análise de alimentos, avaliando o teor em proteínas, tfpidos, glúcidos e cinzas. O perfil individual de açúcares foi determinado por HPLC-RI, os ácidos gordos por GC-FID, os ácidos orgânicos por HPLC-PDA e os tocoferóis por HPLC-fluorescência. Resultados e Discussão: De um modo geral, os parâmetros avaliados mantiveram-se praticamente inalterados, independentemente da espécie vegetal ou da dose de irradiação. Em relação ao perfil em açúcares, as principais modificações consistiram num decréscimo do conteúdo de dissacáridos. As variações mais notáveis em ácidos orgânicos foram observadas nas espécies de plantas com os maiores teores nessas moléculas, particularmente o decréscimo observado nas amostras de cidreira e bretónica. Entre os tocoferóis, as isoformas a e p foram as mais susceptíveis à irradiação, sendo que a aplicação de 1 kGy tendeu a aumentar os níveis de tocoferóis no limonete, enquanto que 10 kGy surtiu o mesmo efeito na bretónica. A amostra de hortelã-pimenta apresentou os níveis mais elevados de tocoferóis, independentemente da dose aplicada. Finalmente, tendo em conta o teor em ácidos gordos, as amostras irradiadas apresentaram maiores valores percentuais de ácidos gordos monoinsaturados do que as amostras controlo. Conclusão: Tendo em conta os efeitos descritos, pode concluir-se que, de um modo geral, a aplicação de irradiação com feixe de eletrões nas doses 1 e 10 kGy é uma forma eficaz de conservar as propriedades químicas e nutricionais das espécies estudada