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- Aplicação dos eurocódigos 0 e 1 – análise comparativa com as congéneres SIA 260 e 261Publication . Ferreira, Débora; Moreno, Carlos; Branco, RicardoOs Eurocódigos 0 e 1 (EN 1990, EN 1991), que substituíram o Regulamento de Segurança e Ações para Estruturas de Edifícios e Pontes (RSAEEP) na quantificação das principais ações a que uma estrutura está sujeita, proporcionaram a uniformização das metodologias de verificação e dimensionamento estrutural a nível da União Europeia. A Suíça é um dos poucos países europeus que continua a seguir normas de dimensionamento internas: as SIA – Société Suisse des Ingénieurs et des Architectes. Para garantir a segurança estrutural há a necessidade de dotar as estruturas de capacidade resistente adequada. Uma das etapas iniciais do processo de dimensionamento consiste na quantificação e combinação das diferentes ações. São abordados, no presente trabalho, as principais ações a considerar no dimensionamento estrutural, bem como os diferentes modelos de combinação das ações.
- Estudo experimental e modelação numérica do punçoamento excêntrico em lajes fungiformesPublication . Moreno, Carlos; Bastos, Ana SarmentoA capacidade resistente das lajes fungiformes é, frequentemente, limitada pela carga de rotura ao punçoamento, habitualmente inferior à carga de rotura por flexão. A investigação do fenómeno do punçoamento tem incidido essencialmente sobre o punçoamento centrado, em relação ao qual se poderá reconhecer que existe, actualmente, um conhecimento razoável aferido pela boa concordância entre as teorias explicativas e os resultados experimentais. Ao invés, os estudos experimentais sobre a influência da excentricidade do carregamento em lajes fungiformes são, ainda, escassos. Por outro lado a análise da regulamentação existente [1-4] evidencia claras diferenças nas recomendações e disposições legais em relação ao punçoamento. O presente trabalho tem como objectivo o estudo por vias experimental e numérica do efeito da excentricidade do carregamento na capacidade resistente última de lajes fungiformes. É avaliada experimentalmente a contribuição da armadura de punçoamento, analisando comparativamente os comportamentos de lajes em betão corrente, com ou sem armadura específica de punçoamento. Descrevem-se os ensaios realizados em seis modelos à escala real de laje quadrada (2.5×2.5×0.18 m3), submetidos a carregamento centrado e com excentricidade de 0.8 da dimensão do pilar central, também quadrado (0.25×0.25 m2). São avaliadas as contribuições da armadura transversal na carga última e na definição do cone de rotura. A excentricidade da carga determina uma redução de 32 % e de 25 % da capacidade resistente ao punçoamento no caso das lajes sem e com armadura transversal, respectivamente. A presença da armadura transversal origina um aumento da carga última de 23 % ou de 34 % nos ensaios sem ou com excentricidade, respectivamente. Os ensaios experimentais são também reproduzidos por simulações numéricas com recurso ao método dos elementos finitos e ao código computacional DIANA [5].
- The use of ultrasonic echo pulse velocity as an NDT method to predict the concrete strength and uniformityPublication . Abreu Filho, Marco Antonio; Moreno, Carlos; Luso, EduardaThe ultrasonic approach is one of the non-destructive testing methods that most technologically progressed in past few years. This study aims to validate the accuracy and capabilities of this method in the mechanical characterization of concrete elements, by using an ultrasonic tomography equipment based in echo pulse velocity (S-waves). The elastic modulus and compressive strength of concrete are estimated from the echo pulse velocity. Furthermore, the uniformity of concrete elements is evaluated. The concrete compression strength prediction was performed on cubic specimens and the reached accuracy was over 91% using the analytical approach proposed on this study. The correlation coefficient between the pulse echo velocity and the uniaxial compression strength found in this study was over 97%. Thus, the use of the ultrasonic NDT to evaluate the uniformity of concrete elements proved to be efficient.
- Punching shear strengthening of flat slabs: CFRP and shear reinforcementPublication . Moreno, Carlos; Ferreira, Débora; Bennani, Abdelkrim; Sarmento, Ana; Noverraz, MichelPunching in slabs is usually associated to the application of concentrated loads or to the presence of columns. One of the main concerns related to flat slabs is its punching shear capacity at slabcolumn connection, which is subjected to a very complex three-dimensional stress state. Provided that bending capacity is installed, punching shear failure is hence characterized by the development of a truncated cone shaped surface at the slab-column connection. The experimental programme carried out by the authors includes four normal strength concrete slabs (1100×1100×100 mm3), with and without shear reinforcement, submitted to punching under a concentrated load. One of the specimens included typical bent-down bars as shear reinforcement. Frequently, there is the need to strengthen existing flat slabs against punching shear failure. Current paper intends to further investigate the structural response of such reinforcement techniques. One of the strengthening practices, which have been tested within current experimental programme, consists on gluing carbon fibre reinforced polymers on concrete surface. Moreover, the near surface mounted technique has also been tested within current experimental work. Finally, a fourth specimen served as reference. The effects of shear reinforcement and of the carbon fibre reinforced polymers enhancing punching shear capacity are observed.
- Punching shear strengthening of flat slabs: CFRP and shear reinforcementPublication . Moreno, Carlos; Ferreira, Débora; Bennani, Abdelkrim; Sarmento, Ana; Noverraz, MichelPunching in slabs is usually associated to the application of concentrated loads or to the presence of columns. One of the main concerns related to flat slabs is its punching shear capacity at slabcolumn connection, which is subjected to a very complex three-dimensional stress state. Provided that bending capacity is installed, punching shear failure is hence characterized by the development of a truncated cone shaped surface at the slab-column connection. The experimental programme carried out by the authors includes four normal strength concrete slabs (1100×1100×100 mm3), with and without shear reinforcement, submitted to punching under a concentrated load. One of the specimens included typical bent-down bars as shear reinforcement. Frequently, there is the need to strengthen existing flat slabs against punching shear failure. Current paper intends to further investigate the structural response of such reinforcement techniques. One of the strengthening practices, which have been tested within current experimental programme, consists on gluing carbon fibre reinforced polymers on concrete surface. Moreover, the near surface mounted technique has also been tested within current experimental work. Finally, a fourth specimen served as reference. The effects of shear reinforcement and of the carbon fibre reinforced polymers enhancing punching shear capacity are observed.
- Experimental and numerical evaluation of bond properties between reinforcement and concretePublication . Moreno, Carlos; Bastos, Ana SarmentoA study of the bond behaviour between steel reinforcement bars and four different types of surrounding concrete: normal strength concrete (NSC), steel fibber reinforced concrete (SFRC) and two structural lightweight aggregate concretes (SLWAC) is here presented. Five beam-tests according to Standard RILEM (1982) [5] were conducted on specimens under monotonously increased loading. Bond-slip response curves between concretes and reinforcement are obtained and discussed. The results obtained show that standard bond length of 10∅d is not adequate to determine bond characteristics of reinforcement in concretes with grades higher than C 25/30. Bond failure of the NSC beam did not occur but the bar itself failed. Bond failure was observed for NSC beam and for LWAC and SFRC beams when reduced bond length of 5∅d was used. A numerical simulation of the beam tests using the finite element method analysis, using bond-slip model of CEB-FIP Model Code 1990 [1] and real properties of test materials, was also carried out and the results are compared with the experimental values.
- Punching shear analysis of slab-column connectionsPublication . Moreno, Carlos; Sarmento, Ana MariaThe paper aims to present an experimental testing program regarding reinforced concrete slabs, with and without shear reinforcement, submitted to punching under both symmetric and eccentric loading. Comparisons between numerical simulations and experimental behaviour results are carried on. The capabilities and limitations of the numerical model to reproduce the brittle punching-shear failure are discussed. The paper opted for a performance assessment of a numerical model, comparing FEM results with known experimental tests properly instrumented. Capability of DIANA software to simulate the punching behaviour of slabs is discussed. The paper demonstrates that the mechanical properties assigned to the element layer containing the bending reinforcement impose the load deflection stiffness behaviour. Good agreement was found between the predicted and the observed deformation behaviour. Nevertheless, the reproduction of the punching ultimate capacity is strongly dependent on the adopted value for the shear retention factor, which appears to be the major decisive parameter. This paper demonstrates that the smeared crack model based on both the concept of strain decomposition (SD) and total strain with fixed orthogonal cracks approach (TSF) can correctly be used for the analysis of the behaviour of slabs submitted to punching shear.
- Punching shear in eccentrical loaded flat slabsPublication . Moreno, Carlos; Bastos, Ana SarmentoThe effect of the eccentricity of loading on the behaviour of slab-column connections without or with headed studs as shear reinforcement is experimentally investigated. Normal and fibre reinforced concrete slabs were experimentally tested. Test results are compared with code provisions and with numerical simulation analyses.
- Strengthening slabs for punching shear using fibre reinforced polymerPublication . Moreno, Carlos; Ferreira, Débora; Sarmento, AnaPunching is generally associated to the application of concentrated loads or to the presence of columns. One of the main concerns related to flat slabs is its punching shear capacity at slab‐column connection, which is subjected to a very complex three‐dimensional stress state. Provided that bending capacity is installed, punching shear failure is characterized by the development of a truncated cone shaped surface at the slab‐column connection. Recurrently, there is the need to strengthen existing flat slabs against punching shear failure. The use of fibre‐reinforced polymer (FRP) is an innovative technology to strengthen concrete structures. In this paper, punching shear strengthening of flat slabs using carbon fibre reinforced polymer (CFRP) is studied. The experimental programme carried out by the authors includes four normal strength concrete slabs (1100×1100×100 mm3), with and without shear reinforcement, submitted to punching under a concentrated load. One of the specimens included typical bent‐down bars as shear reinforcement. Among available strengthening practices, the technique that consists on gluing CFRP on concrete surface have been tested within current experimental programme. Moreover, the near surface mounted (NSM) technique has also been tested within current experiments. Finally, a fourth specimen served as reference. The effects of shear reinforcement and of CFRP enhancing punching shear capacity are observed.
- Application of eurocodes 0 and 1 - comparison with sia 260 and 261 swiss standardsPublication . Branco, Ricardo; Moreno, Carlos; Ferreira, DéboraThe structural safety is one of the most important issues in construction. In order to ensure this safety there is a need to provide the appropriate carrying capacity to the structure. One of the initial stages of the design process is the quantification and combination of the different actions. Eurocodes 0 and 1 (EN 1990, EN 1991) are concerned by defining the basis of structural design and the actions that should normally be considered in the design of buildings and civil engineering works such as imposed load, wind and snow loads, and have brought a consistency of methodologies for structural design across European Union. Switzerland is one of the few countries in Europe which is not included in European Union, and that continues to follow internal standards, the SIA - Swiss Society of Engineers and Architects. Current investigation involved the comparative study of the requirements for safety and serviceability limit states, load combination format, and partial safety factors as well as the main actions to be considered for the structural design and verification. Both codes of practice are analyzed and compared for the different actions. An automatic calculation computer program was also developed during this study in order to estimate the values of the different actions. Finally, a real building was modelled so as to validate the above mentioned program and to analyze the main differences between European and Swiss codes.