Deflection control for reinforced recycled aggregate concrete beams: Experimental database and extension of the fib Model Code 2010 model

Recycled aggregate concrete (RAC) has emerged as a viable solution for solving some of the environmental problems of concrete production. However, design guidelines for deflection control of reinforced RAC members have not yet been proposed. This study presents a comprehensive analysis of the applicability of the fib Model Code 2010 (MC2010) deflection control model to reinforced RAC beams. Three databases of long-term studies on natural aggregate concrete (NAC) and RAC beams were compiled and meta-analyses of deflection predictions by MC2010 were performed. First, the MC2010 deflection control model was tested against a large database of long-term tests on NAC beams. Second, a database of RAC and companion NAC beams was compiled and initial and long-term deflections were calculated using the MC2010 model. It was shown that deflections of RAC beams are significantly underestimated relative to NAC beams. Previously proposed modifications for MC2010 equations for shrinkage strain and creep coefficient were used, and new modifications for the modulus of elasticity and empirical coefficient β were proposed. The improved MC2010 deflection control model on RAC beams was shown to have equal performance to that on companion NAC beams. The proposals presented in this paper can help engineers to more reliably perform deflection control of reinforced RAC members.This is the peer-reviewed version of the article: N. Tošić, S. Marinković, and J. de Brito, ‘Deflection control for reinforced recycled aggregate concrete beams: Experimental database and extension of the fib Model Code 2010 model’, Structural Concrete, vol. 20, no. 6, pp. 2015–2029, 2019 [https://doi.org/10.1002/suco.201900035

Assessment of damage localization based on spatial filters using numerical crack propagation models

This paper is concerned with vibration based structural health monitoring with a focus on non-model based damage localization. The type of damage investigated is cracking of concrete structures due to the loss of prestress. In previous works, an automated method based on spatial filtering techniques applied to large dynamic strain sensor networks has been proposed and tested using data from numerical simulations. In the simulations, simplified representations of cracks (such as a reduced Young's modulus) have been used. While this gives the general trend for global properties such as eigen frequencies, the change of more local features, such as strains, is not adequately represented. Instead, crack propagation models should be used. In this study, a first attempt is made in this direction for concrete structures (quasi brittle material with softening laws) using crack-band models implemented in the commercial software DIANA. The strategy consists in performing a non-linear computation which leads to cracking of the concrete, followed by a dynamic analysis. The dynamic response is then used as the input to the previously designed damage localization system in order to assess its performances. The approach is illustrated on a simply supported beam modeled with 2D plane stress elements. © 2011 Published under licence by IOP Publishing Ltd.info:eu-repo/semantics/publishe

The foundations of the Nieuwe Kerk Tower in Amsterdam (1645-52)

In 1645, the Amsterdam mayors planned to build a tower onto the Nieuwe Kerk (New Church), which was to become the tallest in the Dutch Republic. Although this structure was never completed, construction started in 1646. The urban location forced the builders to dam the water of the canal, into which the new tower was to be partly built. Thanks to the discovery of detailed data, such as written sources, drawings and wooden models, it is possible to analyze how the tower was planned. Combined with information about foundation technology, materials used, the number of people involved in construction, etc., a detailed insight into the construction process has been obtained and the foundation technique—a combination between old fashioned and modern practices—can be analyzed

De l'utilisation de fibres métalliques comme armature complémentaire de poutres en béton armé soumises à flexion

SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Rigidité d'une zone tendue de béton armé

Non linear methods for computing deflections of reinforced concrete linear structures in cracked stage are now spreading rapidly. In some latest reinforced concrete codes and manuals, the basic assumption regarding such calculations lies in the relationship between the mean steel (or concrete) strain and the steel strain in a fully cracked section. The authors have established a state-of-the-art for such relationships. All proposed formulas can practically be written in the following form: {Mathematical expression} where ε m stands for the mean steel and concrete strain, ε s the steel strain in a cracked section and where Δθ represents the tension stiffening effect of concrete lying between the cracks. Various propositions have been made for the relationship between Δθ and the steel stress (e.g. constant, linear, hyperbolic,); other important factors too are the strength of concrete in tension and the reinforcement ratio. Considering that little experimental evidence supports the various propositions, an experimental program on thirteen reinforced concrete prisms (ties) subjected to uniaxial tension was carried out. The influence of the reinforcement ratio is especially studied. Careful assessment of the validity of previous formulas is made. A new bilinear relationship between the tension stiffening effect and the steel stress is proposed for analytical calculations. © 1985 Bordas-Gauthier-Villars.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Experimental assessment of the pull-out strength of single rods bonded in glulam parallel to the grain

IF (ISI) = 0,885info:eu-repo/semantics/publishe