79 research outputs found
Time-dependent fibre pull-out behaviour in self-compacting concrete
In the present study, the effectiveness of a fibre as an element for transferring stresses across cracks under a sustained
load was assessed. Single fibre pull-out creep tests were performed, in which fibre slip was monitored as a function
of the time. The influence of the fibre orientation angle (0, 30 and 60 degrees), as well as pre-imposed fibre slip levels,
spr, 0.3 and 0.5 mm on the creep response was investigated. Additionally, instantaneous fibre pull-out tests were carried
out on undamaged-bond specimens in order to quantify the effects of the pull-out creep behaviour. The damage
introduced by the pre-slip levels in the bond of the fibre/matrix interface influenced the long-term fibre pull-out
behaviour and, consequently, accelerated the creep rate. However, the assembled pull-out creep behaviour did not
differ considerably from the instantaneous pull-out behaviour for the adopted pre-imposed fibre slip levels.This work is supported by the FEDER funds through the Operational Program for Competitiveness Factors -
COMPETE and National Funds through FCT - Portuguese Foundation for Science and Technology under the project 18 SlabSys-HFRC-PTDC/ECM/120394/2010. The authors would like to acknowledge the materials supplied by Radmix and Maccaferri (fibres), SECIL (cement), SIKA and BASF (superplasticizers), Omya Comital (limestone filler), and Pegop (Fly ash).info:eu-repo/semantics/publishedVersio
Relation between fibre distribution and post-cracking behaviour in steel fibre reinforced self-compacting concrete panels
In this research, the influence of the fibre distribution and orientation on the post-cracking behaviour of steel fibre
14 reinforced self-compacting concrete (SFRSCC) panels was studied. To perform this evaluation, SFRSCC panels
15 were cast from their centre point. For each SFRSCC panel, cylindrical specimens were extracted and notched either
16 parallel or perpendicular to the concrete flow direction, in order to evaluate the influence of fibre dispersion and
17 orientation on the tensile performance. The post-cracking behaviour was assessed by both splitting tensile tests and
18 uniaxial tensile tests. To assess the fibre density and orientation through the panels, an image analysis technique was
19 employed across cut planes on each tested specimen. It is found that the splitting tensile test overestimates the post20
cracking parameters. Specimens with notched plane parallel to the concrete flow direction show considerable higher
21 post-cracking strength than specimens with notched plane perpendicular to the flow direction.The studies reported in this paper are part of the research project LEGOUSE (QREN, project no 5387). This project is co-supported by FEDER through COMPETE programme ("Programa Operacional Factores de Competitividade"). The materials were supplied by Radmix and Maccaferri (fibres), SECIL (cement), SIKA and BASF (superplasticizers), Omya Comital (limestone filler), and Pegop (Fly ash)
Quantificação do carbono das substâncias húmicas em diferentes sistemas de uso do solo e épocas de avaliação.
A quantificação do carbono nas diferentes frações da matéria orgânica do solo (MOS) torna-se necessária devido ao interesse de se conhecer o potencial de captura e armazenamento do carbono nos diferentes sistemas de uso do solo. O objetivo deste trabalho foi quantificar o carbono das substâncias húmicas em diferentes sistemas de uso do solo e épocas de avaliação e correlacioná-lo com algumas propriedades quÃmicas e fÃsicas do solo. Os sistemas selecionados foram: preparo convencional (PC-milho/feijão), plantio direto (PD-berinjela/milho), consórcio maracujá/Desmodium sp, cultivo com figo e sistema agroflorestal. As amostras de solo foram coletadas em duas profundidades (0-5 e 5-10 cm) e épocas (17/11/2005–verão e 23/6/2006-inverno). Foi determinado o carbono orgânico total (COT) e realizado o fracionamento quÃmico da MOS, quantificando-se o carbono da fração humina (C-HUM), fração ácido húmico (C-FAH) e fração ácido fúlvico (C-FAF). O C-HUM constituiu a maior parte do COT, havendo correlação significativa com o COT em todos os sistemas avaliados e estações. Analisando o C-FAH foi possÃvel identificar alterações no solo relacionadas aos sistemas de uso, na profundidade de 0-5 cm e no verão, destacando-se o PD com os maiores teores. Com o C-FAF ocorreu este mesmo comportamento, mas na profundidade de 5-10 cm e no inverno, destacando-se o PC com maiores valores. Foram verificadas correlações significativas entre Valor S, Valor T e DMP em todos os sistemas, com exceção da área de PC. O PD aumenta os teores de C-FAH, nas duas profundidades e nas duas estações, quando comparado ao PC do solo
A model for the prediction of the punching resistance of steel fibre reinforced concrete slabs centrically loaded
With the aim of contributing for the development of design guidelines capable of predicting with high
accuracy the punching resistance of steel fibre reinforced concrete (SFRC) flat slabs, a proposal is presented
in the present paper and its predictive performance is assessed by using a database that collects the
experimental results from 154 punching tests. The theoretical fundaments of this proposal are based on the
critical shear crack theory proposed by Muttoni and his co-authors. The proposal is capable of predicting the
load versus rotation of the slab, and attends to the punching failure criterion of the slab. The proposal takes
into account the recommendations of the most recent CEB-FIP Model Code for modelling the post-cracking
behaviour of SFRC. By simulating the tests composing the collected database, the good predictive
performance of the developed proposal is demonstrated.Fundação para a Ciência e a Tecnologia (FCT
Assessment of different methods for characterization and simulation of post-cracking behavior of self-compacting steel fiber reinforced concrete
The post-cracking tensile properties of steel fiber reinforced concrete (SFRC) is one of the most important aspects that should be considered in design of SFRC structural members. The parameters that describe the post-cracking behavior of SFRC in tension are often derived using indirect methods combined with inverse analysis techniques applied to the results obtained from three- or four-point prism bending tests or from determinate round panel tests. However, there is still some uncertainty regarding the most reliable methodology for evaluating the post-cracking behavior of SFRC. In the present study a steel fiber reinforced self-compacting concrete (SFRSCC) was developed and its post-cracking behavior was investigated through an extensive experimental program composed of small determinate round panel and prism bending tests. Based on the results obtained from this experimental program, the constitutive tensile laws of the developed SFRSCC were obtained indirectly using two numerical approaches, as well as three available analytical approaches based on standards for estimating the stress versus crack width relationship (). The predictive performance of both the numerical and analytical approaches employed for estimating the relationship of the SFRSCC was assessed. The numerical simulations have provided a good prediction of the post-cracking behavior of the concrete. All the analytical formulations also demonstrated an acceptable accuracy for design purposes. Anyhow, among all the employed approaches, the one that considers the results of small determinate round panel tests (rather than that of prism bending tests) has predicted more accurately the constitutive tensile laws of the SFRSCCFEDER funds through the Operational Programme for
Competitiveness and Internationalization - COMPETE and by national funds through FCT (Portuguese Foundation for Science and Technology) within the scope of the project InOlicTower, POCI-01-0145-FEDER520 016905 (PTDC/ECM-EST/2635/2014)
Thimet oligopeptidase (EC 3.4.24.15) key functions suggested by knockout mice phenotype characterization
Thimet oligopeptidase (THOP1) is thought to be involved in neuropeptide metabolism, antigen presentation, neurodegeneration, and cancer. Herein, the generation of THOP1 C57BL/6 knockout mice (THOP1(-/-)) is described showing that they are viable, have estrus cycle, fertility, and a number of puppies per litter similar to C57BL/6 wild type mice (WT). In specific brain regions, THOP1(-/-) exhibit altered mRNA expression of proteasome beta5, serotonin 5HT2a receptor and dopamine D2 receptor, but not of neurolysin (NLN). Peptidomic analysis identifies differences in intracellular peptide ratios between THOP1(-/-) and WT mice, which may affect normal cellular functioning. In an experimental model of multiple sclerosis THOP1(-/-) mice present worse clinical behavior scores compared to WT mice, corroborating its possible involvement in neurodegenerative diseases. THOP1(-/-) mice also exhibit better survival and improved behavior in a sepsis model, but also a greater peripheral pain sensitivity measured in the hot plate test after bradykinin administration in the paw. THOP1(-/-) mice show depressive-like behavior, as well as attention and memory retention deficits. Altogether, these results reveal a role of THOP1 on specific behaviors, immune-stimulated neurodegeneration, and infection-induced inflammation
In situ estimation of indigestible compounds contents in cattle feed and feces using bags made from different textiles
Uso de malhas pigmentadas e mulching em túneis para cultivo de rúcula: efeito no ambiente e nas plantas modelo
Efeito da radiação gama na absorção de água e no tempo de cocção em cultivares de soja
Canine cutaneous leishmaniasis by Leishmania (Viannia) braziliensis in an agricultural settlement, endemic area for leishmaniasis
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