References of "Denoël, Vincent"
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See detailOn the influence of background component in resonance of cables
Canor, Thomas ULg; Denoël, Vincent ULg

in 9th International Symposium on Cable Dynamics: ISCD 2011, Proceedings (2011)

This work deals with nonlinear dynamical behaviour of cables in the context of random excitations of one of its anchors. Different studies have already been realized, that highlight different cable ... [more ▼]

This work deals with nonlinear dynamical behaviour of cables in the context of random excitations of one of its anchors. Different studies have already been realized, that highlight different cable responses under random excitations such as white noise or narrow band processes. This work can be seen as an extension of these former works. It aims at modeling a more realistic random excitation by associating a background component to a resonant excitation. The background component models the effects of turbulence on the structure and the resonant component results from structural vibrations of the primary system. Any direct excitation on the cable is disregarded in this work. The first part of this paper describes the model and the random excitation generators. The second part deals with the influence of the background component on the possible resonance of a cable. Results are presented for a given level of energy in the excitation, and as a function of its dispatching between the background and resonant components. This work shows that the background component reduces the vibration in the out-of-plane mode and can avoid resonance from taking place. The on-off intermittency phenomenon is also observed for the out-of-plane mode and it depends also on the background component. [less ▲]

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See detailVandalism Prevention of a Footbridge with Cable Vibrations
Canor, Thomas ULg; Kerschen, Gaëtan ULg; Denoël, Vincent ULg

in Biliszczuk, Jan; Bien, Jan; Hawryszkow, Pawel (Eds.) et al 4th International Conference Footbridge : Attractive structures at reasonable costs, Wroclaw 6-8 July 2011 (2011)

This work studies an unusual way to improve comfort of a footbridge with cables. Cables can be seen as a means of dissipating energy in a structure. This complementary source of dissipation does not ... [more ▼]

This work studies an unusual way to improve comfort of a footbridge with cables. Cables can be seen as a means of dissipating energy in a structure. This complementary source of dissipation does not prohibit resonance from taking place, but it is a way to limit vibrations and to impede vandals’ actions. This study is illustrated with measurements realized on a specific footbridge. This structure is a metallic arch characterized by a first natural frequency of 3.2Hz and a corresponding damping ratio of 0.55%. Intolerable accelerations (around 6m/s²) are easily reached when an ill-intentioned person is bouncing at an appropriate frequency. After installation of a single cable at a suitable location in the structure, the measured damping ratios are almost doubled and the maximum accelerations at resonance are reduced by 30%. With three cables on the footbridge, the damping ratio becomes significantly nonlinear: it reaches up to 3% for low amplitude oscillations, but drops down to 1% for moderate to high amplitudes. For higher accelerations, it does not seem to depend on the number of cables. According to these observations, a notable effect of cables is to reduce the maximum acceleration, but the main effect is to prolong the transient phase and to make the resonance frequency hardly identifiable by vandals. [less ▲]

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See detailInfluence of bridge deck shape on extreme buffeting forces
Flamand, Olivier; Denoël, Vincent ULg

in Proceedigs of 13th International Conference on Wind Engineering (2011)

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See detailBackground/BiResonant decomposition of the non Gaussian buffeting response
Denoël, Vincent ULg

in Proceedigs of 13th International Conference on Wind Engineering (2011)

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See detailEulerian Formulation of Constrained Elastica
Denoël, Vincent ULg; Detournay, Emmanuel

in International Journal of Solids and Structures (2011), 136

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See detailUsing 3D to understand human motion
Schwartz, Cédric ULg; Forthomme, Bénédicte ULg; Bruls, Olivier ULg et al

Poster (2010, December)

The understanding and tracking of human motion has been a subject of interest in the scientific community for more than one century. The long history of human motion analysis comes from the large scope of ... [more ▼]

The understanding and tracking of human motion has been a subject of interest in the scientific community for more than one century. The long history of human motion analysis comes from the large scope of applications of such measurement that can be found in medicine, biomechanics, sport, ergonomics, and even civil engineering. More recently, those technologies have also been widely exploited for the development of animation movies and games. Needless to say, the techniques used one century ago significantly differ from those used today. This paper describes in a first part the evolution of the technological capabilities for motion analysis and the actual limitations. From this analysis and in a second part, we describe the experience related to the creation of a motion analysis laboratory at the University of Liège and show how such a platform could be the center of a multidisciplinary research and provide valuable information to various communities. [less ▲]

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See detailPatching asymptotic solution of a cable with a small bending stiffness
Canor, Thomas ULg; Denoël, Vincent ULg

in Proceedings of the IVth European Conference on Computational Mechanics (2010)

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See detailStochastic analysis of a stadium roof from deterministic wind tunnel measurements
Blaise, Nicolas ULg; Denoël, Vincent ULg

in 13th International Conference on Wind Engineering (2010)

Dynamic analyses of structures under buffeting wind loads can be performed in a deterministic (Clough and Penzien, 1997) or stochastic (Preumont, 1994) context, both with a modal approach for ... [more ▼]

Dynamic analyses of structures under buffeting wind loads can be performed in a deterministic (Clough and Penzien, 1997) or stochastic (Preumont, 1994) context, both with a modal approach for computational efficiency reasons. In the first option, the forces are deterministically given, and the uncoupled modal equations of motion are solved either in the time domain with a stepby- step method, either in the frequency domain, with Fourier transformation. In the second option, the analysis relies on the determination of the Power Spectral Density (PSD) matrix of the structural response given that of the loading. The choice of one or another method usually depends on whether the loading is provided in the time or frequency domain and as a deterministic (a single time history) or stochastic manner. From a designer’s point of view, the wind loading can be defined using design codes (e.g. Eurocode, 2005) where analytical expressions of (i) the PSD of wind velocities (Davenport, Von Karman, etc) (ii) the coherence functions and (iii) the pressure coefficients are given to compute, finally, (iv) the PSD of the aerodynamic pressures. Design engineers are usually familiar with this probabilistic approach. Alternatively, the design may be conducted from aerodynamic pressures measured in a wind tunnel. This approach is more realistic than the aforementioned codified procedure since a number of phenomena as (a) the aerodynamic instabilities, (b) aerodynamic admittance (Scanlan and Jones, 1999), (c) site effects are taken into account. Pressures are thus given as unique (deterministic) time histories at each sensor. In a Finite Element context and a modal analysis, the generalized forces are computed from the measured pressures. With the firm wish to perform the analysis in a stochastic manner (for a number of good reasons mentioned next), we suggest to fit a probabilistic model to the measured data. Such a model could be fitted to the measured pressures right away, or any other subsequent quantity such as the generalized forces. The following discussion is about the most favorable quantity that has to be fitted and how to do it appropriately in view of typical measurement imperfections. [less ▲]

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See detailMultiple scales solution for a beam with a small bending stiffness
Denoël, Vincent ULg; Detournay, Emmanuel

in Journal of Engineering Mechanics (2010), 136(1), 69-77

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See detailThe problem of a drillstring inside a curved borehole: a perturbed Eulerian approach
Denoël, Vincent ULg; Detournay, Emmanuel

(2009, February)

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See detailAsymptotic expansion of slightly coupled modal dynamic transfer functions
Denoël, Vincent ULg; Degée, Hervé ULg

in Journal of Sound & Vibration (2009), 328

In case of non-diagonal modal damping, normal modes of vibration do not decouple modal equations. The usual way to handle such a non-diagonal modal damping matrix is to neglect its off-diagonal elements ... [more ▼]

In case of non-diagonal modal damping, normal modes of vibration do not decouple modal equations. The usual way to handle such a non-diagonal modal damping matrix is to neglect its off-diagonal elements. In this paper, we propose an approximatemethod based on an asymptotic expansion of the transfer function. It is intermediate between the classical decoupling approximation and the formal solution requiring a full matrix inversion. Indeed, on the one hand, it allows to partially account for modal coupling and, on the other hand, still allows the modal equations to be solved independently from each other. We first provide the mathematical background necessary to canvass the proposed method, then consider a benchmark against which the benefits of the method are measured. [less ▲]

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See detailPolynomial approximation of aerodynamic coefficients based on the statistical description of the wind incidence
Denoël, Vincent ULg

in Probabilistic Engineering Mechanics (2009), 24(2), 179-189

In civil engineering applications, the aerodynamic coefficients are usually measured in wind tunnels for several wind incidences. The measurement results need to be linearized in order to perform the ... [more ▼]

In civil engineering applications, the aerodynamic coefficients are usually measured in wind tunnels for several wind incidences. The measurement results need to be linearized in order to perform the design of the structure. This paper justifies the use of different linearization techniques for different assessments as divergence or buffeting analysis. In this latter context, it is proposed to linearize the aerodynamic coefficient by the least-square method, using the probability density function of the wind incidence as a weighting function. First this probability density function is computed for a 2-D wind flow, as a function of the wind intensities and their correlation. Then, the comparison of results from different linearization techniques provides surprising results indicating that what is usually performed should be considered with care. [less ▲]

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See detailMultiple mode analysis of the self-excited vibrations of rotary drilling systems
Germay, Christophe; Denoël, Vincent ULg; Detournay, Emmanuel

in Journal of Sound & Vibration (2009), 325(1-2), 362-381

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See detailLimit analysis of the statistics of quasi-steady non-linear aerodynamic forces for small turbulence intensities
Denoël, Vincent ULg

in Probabilistic Engineering Mechanics (2009), 24(4), 552-564

This paper focuses on the estimation of statistical characteristics of a specific quasi-steady wind loading used in buffeting analyses. In this loading, the intrinsic non-linearity of aerodynamic ... [more ▼]

This paper focuses on the estimation of statistical characteristics of a specific quasi-steady wind loading used in buffeting analyses. In this loading, the intrinsic non-linearity of aerodynamic coefficients is considered and approached by a polynomial expression of any a priori chosen degree. As rigorous developments of the statistical moments would result in impractical formulations, we suggest to consider the smallness of the turbulence intensities to construct, by means of a limit analysis, approximate expressions of the raw moments of aerodynamic forces. From these expressions, approximate cumulants and associated dimensionless characteristics, such as skewness and excess coefficients, are derived. The accuracy of the proposed analytical relations is assessed by comparison with Monte Carlo simulations, and the relevance of the sophisticated non-linear loading under consideration is compared to more traditional models. [less ▲]

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See detailEstimation of modal correlation coefficients from background and resonant responses
Denoël, Vincent ULg

in Structural Engineering and Mechanics: an International Journal (2009), 32(6), 725-740

A new simple relation for the estimation of modal correlation coefficients is presented. It is obtained from the decomposition of covariances of modal responses into background and resonant contributions ... [more ▼]

A new simple relation for the estimation of modal correlation coefficients is presented. It is obtained from the decomposition of covariances of modal responses into background and resonant contributions, as it is commonly done for the variances. Thanks to appropriate assumptions, the modal correlation coefficients are estimated as weighted sums of two limit values, corresponding to the background and resonant responses respectively. The weighting coefficients are expressed as functions of the background-to-resonant ratios, which makes the proposed formulation convenient and easily accessible. The simplicity of the mathematical formulation facilitates the physical interpretation. It is for example proved that modal correlation coefficients can be non negligable even in case of well separated natural frequencies, which is sometimes unclear in the litterature. The new relation is mainly efficient in case of large finite element models. It is applied and validated on a finite element buffeting analysis of the Viaduct of Millau, the highest bridge deck ever built so far. [less ▲]

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See detailDynamic interaction between merchandizes and supporting structure in steel storage racking systems
Degée, Hervé ULg; Denoël, Vincent ULg

in Proceedings of the COMPDYN 2009 Conference (2009)

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See detailTornades, vents exceptionnels et constructions
Denoël, Vincent ULg

Learning material (2008)

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See detailAdvantages of a semi-analytical approach for the analysis of an evolving structure with contacts
Denoël, Vincent ULg

in Communications in Numerical Methods in Engineering (2008), 24(12), 1667-1683

This paper presents a semi-analytical approach for the evolution analysis of a beam into given boundaries. The analytical description of contact locations, contact forces and beam deflections results in ... [more ▼]

This paper presents a semi-analytical approach for the evolution analysis of a beam into given boundaries. The analytical description of contact locations, contact forces and beam deflections results in an exact modelling of the phenomenon (no penetration allowed). Despite the apparent complexity of the problem, the analytical relations leading to two-point boundary and integro-restrained differential equations are formally written. An iterative resolution of these equations is adopted by converting the problem into a single-point boundary value one. Due to a proper selection of the global unknowns, namely the contact forces and their locations, the proposed method is particularly efficient in the context of evolving structures. The resolution is illustrated on a simple example, and comparisons with the finite element method are given as persuasive arguments. Copyright © 2007 John Wiley & Sons, Ltd. [less ▲]

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