26 research outputs found

    Determination by analytical approach of the characteristics in free vibration of a complex asymmetric structure

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    In this paper, a new analytical calculation method is presented to study the free vibration behavior of a tall building structure with constant properties over its entire height. The proposed calculation method is based on Alembert's principle, and the continuum approach of a structure composed of walls, frames, and structural cores arranged asymmetrically according to the plane of the floor. The main idea of the present model is to associate both the coupling effect of the flexural stiffness and the shear stiffness in the differential equations governing the free vibration behavior of the structure. The analysis focuses on the determination of the free coupled vibration characteristics. According to the two orthogonal directions, the lateral bending-shear vibrations are coupled to the torsional vibrations of St-Venant. A generalized solution method is proposed using the Galerkin approach to determine the frequencies and associated mode shapes of coupled free vibration structures. The obtained results were in good agreement with those found in the literature

    Determination by analytical approach of the characteristics in free vibration of a complex asymmetric structure

    Get PDF
    In this paper, a new analytical calculation method is presented to study the free vibration behavior of a tall building structure with constant properties over its entire height. The proposed calculation method is based on Alembert's principle, and the continuum approach of a structure composed of walls, frames, and structural cores arranged asymmetrically according to the plane of the floor. The main idea of the present model is to associate both the coupling effect of the flexural stiffness and the shear stiffness in the differential equations governing the free vibration behavior of the structure. The analysis focuses on the determination of the free coupled vibration characteristics. According to the two orthogonal directions, the lateral bending-shear vibrations are coupled to the torsional vibrations of St-Venant. A generalized solution method is proposed using the Galerkin approach to determine the frequencies and associated mode shapes of coupled free vibration structures. The obtained results were in good agreement with those found in the literature

    Influence of the lamination on the redundancy of a horizontally layered glass element and analysis of the debonding of the adhesive interlayer

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    International audienceIt is now recognized that lamination enables to increase the redundancy of glass elements. This paper aims to quantify the possibilities of delamination between panes as well as the increase of redundancy for a horizontally layered glass element thanks to an analytical approach combined with a numerical modeling. From an analytical point of view, new procedures have been defined, taking into account the shear-lag effect as well as the mean curvature of the various adherents. The equilibrium of an infinitesimal element of the laminated structure has enabled to evaluate the interfacial stresses responsible for debonding phenomena. Based on this first approach and on the values of the interfacial stresses, a FE numerical simulation has been calibrated. This calibration is extended in two ways. First, the nonlinear behavior of the material is considered. A smeared crack approach is used to take into account the glass mechanical behavior. Then, a local debonding model involving the use of normal and shear springs is proposed at the interface between two glass panes. The mechanical behaviors of the springs are calibrated by simulating existing tension adhesion tests. Finally, by considering various structural cases, this work concludes that the debonding of the interface is a possibility and discusses its influence on the redundancy of the considered laminated structure

    Buckling of composite non local or gradient connected beams

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    International audienceThe buckling of an axially loaded elastic composite beam with a nonlocal core or a nonlocal connection system is studied in this paper. The composite beam or the sandwich beam is composed of two Euler–Bernoulli beams with a nonlocal elastic interaction. This nonlocal interaction is physically based on the Reissner's model based on three-parameters' interaction function. The energy equations are first presented, and the differential equations are rigorously obtained from a variational principle. We show that the connection model can be expressed in an integral format, therefore, inducing the nonlocal character of this beam elastic interaction model. Furthermore, the variational format of this nonlocal composite model is given, leading to meaningful natural and higher-order boundary conditions. The system of these differential equations can be reduced to a single 10th-order differential equation. We present an exact method to solve this stability problem, based on Ferrari or Cardano's method. The solution can be fully simplified in case of specific boundary conditions with symmetrical considerations. The stability domain is analytically characterized in the loading space for the pinned–pinned boundary conditions. The correspondence between the buckling of the nonlocal composite column and the shear composite column is discussed. Finally, it is shown that the Timoshenko beam model is a nonlocal integral model

    Thermomechanical Analysis of Glass Powder Based Eco-concrete Panels: Limitations and Performance Evaluation

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    This article presents a comprehensive investigation into the thermomechanical analysis of glass powder as an additive in concrete. The efficient Eshelby's model is utilized to determine the relevant composite properties, considering the spherical shape of the glass powder. A higher-order shear deformation plate theory is employed to theoretically simulate the reinforced concrete panel, ensuring accuracy and simplicity. Equilibrium equations are derived using the virtual work concept, and energy equations are derived using Hamilton's principle. Navier's analytical techniques are applied to obtain closed-form solutions for simply supported plates. A comprehensive parametric study is conducted, analyzing the impact of factors such as glass powder volume, geometric parameters, and thermal loading on the thermomechanical behavior of the panel. The findings highlight the challenges associated with using glass powder in concrete for thermomechanical applications and suggest the need for alternative approaches to optimize its effectiveness in such scenarios, also the study provides first-time numerical results that serve as guidelines for further research on reinforced concrete

    Recyclage du ciment dans le ciment : incorporation des déchets de construction et de démolition dans le cru cimentier

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    The European "SeRaMCo" project aims to manufacture precast concrete elements containing recycled aggregates and "recycled" cement. This cement is obtained by incorporating construction and demolition waste into its raw material, in particular the fine fraction which is the richest in hardened cement paste. This PhD thesis provided a better understanding of the impact of the chemical and mineralogical variability of recycled aggregates on the incorporation rate and on the proportion of other raw materials. Laboratory syntheses and associated characterizations allowed to follow the evolution of the mineralogy during the rise in temperature and for several types and rates of recycled aggregates. Tests, including transmission electron microscopy, have also shown that for a high rate of incorporation, the presence of quartz, feldspar and ceramic can affect the burnability of the cement raw meal and the reaction mechanisms. In partnership with the cement manufacturer VICAT, the work has shown that it is possible to produce an industrial "recycled" cement with usual properties by adjusting the manufacturing process as needed or by reducing the rate of incorporation. Even a limited incorporation rate allows to recover easily the waste available on a regional scale from a cement plant while preserving its natural resources. This work also offers new perspectives for the recovery of other materials in cement works and the study of their reactivity.Le projet Européen « SeRaMCo » vise à la fabrication d’éléments préfabriqués en béton contenant des granulats recyclés et du ciment « recyclé ». Ce ciment est fabriqué en incorporant des déchets de construction et de démolition dans le cru cimentier, notamment la fraction fine qui est la plus riche en pâte de ciment durci. Cette thèse de doctorat a permis de mieux comprendre l’impact de la variabilité chimique et minéralogique des granulats recyclés sur le taux d’incorporation et sur la proportion des autres constituants du cru. Les synthèses en laboratoire et caractérisations associées ont permis de suivre l’évolution de la minéralogie au cours de l’élévation de la température et pour plusieurs types et taux de granulats recyclés. Les essais ont aussi montré, notamment par microscopie électronique en transmission, que pour un taux élevé d’incorporation, la présence de quartz, de feldspath et de céramique peut altérer l’aptitude à la cuisson du cru et les mécanismes réactionnels. En partenariat avec le cimentier VICAT, les travaux ont prouvé qu’il est possible de produire un ciment « recyclé » industriel aux propriétés usuelles en ajustant au besoin le procédé de fabrication ou en réduisant le taux d’incorporation. Un taux d’incorporation même limité permet de valoriser sans difficultés les déchets disponibles à l’échelle régionale d’une cimenterie en préservant ses ressources naturelles. Ces travaux offrent également de nouvelles perspectives quant à la valorisation d’autres matériaux en cimenterie et l’étude de leur réactivité

    Recycling of cement in cement : Incorporation of Construction and Demolition Waste in cement raw meal

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    Le projet Européen « SeRaMCo » vise à la fabrication d’éléments préfabriqués en béton contenant des granulats recyclés et du ciment « recyclé ». Ce ciment est fabriqué en incorporant des déchets de construction et de démolition dans le cru cimentier, notamment la fraction fine qui est la plus riche en pâte de ciment durci. Cette thèse de doctorat a permis de mieux comprendre l’impact de la variabilité chimique et minéralogique des granulats recyclés sur le taux d’incorporation et sur la proportion des autres constituants du cru. Les synthèses en laboratoire et caractérisations associées ont permis de suivre l’évolution de la minéralogie au cours de l’élévation de la température et pour plusieurs types et taux de granulats recyclés. Les essais ont aussi montré, notamment par microscopie électronique en transmission, que pour un taux élevé d’incorporation, la présence de quartz, de feldspath et de céramique peut altérer l’aptitude à la cuisson du cru et les mécanismes réactionnels. En partenariat avec le cimentier VICAT, les travaux ont prouvé qu’il est possible de produire un ciment « recyclé » industriel aux propriétés usuelles en ajustant au besoin le procédé de fabrication ou en réduisant le taux d’incorporation. Un taux d’incorporation même limité permet de valoriser sans difficultés les déchets disponibles à l’échelle régionale d’une cimenterie en préservant ses ressources naturelles. Ces travaux offrent également de nouvelles perspectives quant à la valorisation d’autres matériaux en cimenterie et l’étude de leur réactivité.The European "SeRaMCo" project aims to manufacture precast concrete elements containing recycled aggregates and "recycled" cement. This cement is obtained by incorporating construction and demolition waste into its raw material, in particular the fine fraction which is the richest in hardened cement paste. This PhD thesis provided a better understanding of the impact of the chemical and mineralogical variability of recycled aggregates on the incorporation rate and on the proportion of other raw materials. Laboratory syntheses and associated characterizations allowed to follow the evolution of the mineralogy during the rise in temperature and for several types and rates of recycled aggregates. Tests, including transmission electron microscopy, have also shown that for a high rate of incorporation, the presence of quartz, feldspar and ceramic can affect the burnability of the cement raw meal and the reaction mechanisms. In partnership with the cement manufacturer VICAT, the work has shown that it is possible to produce an industrial "recycled" cement with usual properties by adjusting the manufacturing process as needed or by reducing the rate of incorporation. Even a limited incorporation rate allows to recover easily the waste available on a regional scale from a cement plant while preserving its natural resources. This work also offers new perspectives for the recovery of other materials in cement works and the study of their reactivity

    FIBERS ORIENTATION OPTIMIZATION FOR CONCRETE BEAM STRENGTHENED WITH A CFRP BONDED PLATE: A COUPLED ANALYTICAL-NUMERICAL INVESTIGATION

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    Important failure mode of such plated beams is the debonding of the FRP plates from the concrete due to high level of stress concentration in the adhesive at the ends of the FRP plate. This paper presents a new method for reducing interfacial stresses in a concrete beam bonded with the FRP plate by including the effect of the fiber orientation in the FRP plate. This work is divided into two parts; the first one is based on the laminates theory for the analytical solution where a minimization method is used to directly determine the fiber orientation reducing the interfacial stresses. The second part consists into a Finite Element modeling where the analytical solution and different fibers orientation combinations are tested for improving strengthening quality. Numerical results from the present analysis are presented in order to show the advantages of the present solution over existing ones and to reconcile debonding stresses with strengthening quality
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