References of "Denoël, Vincent"
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See detailEfficient uncoupled stochastic analysis with non-proportional damping
Canor, Thomas ULg; Blaise, Nicolas ULg; Denoël, Vincent ULg

in Journal of Sound & Vibration (2012), 331(2012), 52835291

The use of normal modes of vibration in the analysis of structures with nonproportional damping reduces the size of the resulting set of governing equations, but does not decouple them. A common practice ... [more ▼]

The use of normal modes of vibration in the analysis of structures with nonproportional damping reduces the size of the resulting set of governing equations, but does not decouple them. A common practice consists in decoupling the equations by disregarding the o -diagonal elements in the modal damping matrix. Recently, an approximation based on an asymptotic expansion of the modal transfer matrix has been proposed in a deterministic framework to partially account for o -diagonal terms, but still with a set of uncoupled equations. This paper aims at extending this method in a stochastic context. First the mathematical background is introduced and the method is illustrated with a simple example. Then its relevance is demonstrated within the context of the structural analysis of a large and realistic structure. [less ▲]

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See detailApplication of deterministic and stochastic analysis to calculate a stadium with pressure measurements in wind tunnel
Blaise, Nicolas ULg; Denoël, Vincent ULg; De Ville De Goyet, Vincent ULg et al

in Proceedings of the 8th International Conference on Structural Dynamics EURODYN 2011 (2011, July)

This paper aims at comparing different analysis methods in the design of a roof subjected to buffeting wind forces. The specificity of this study is that pressures acting on the stadium roof are measured ... [more ▼]

This paper aims at comparing different analysis methods in the design of a roof subjected to buffeting wind forces. The specificity of this study is that pressures acting on the stadium roof are measured in a wind tunnel. The key idea is to fit a probabilistic model onto the measured data and to perform the stochastic analysis as a usual buffeting analysis. [less ▲]

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See detailReproducibility and repeatability of upper limb landmarks palpation for junior operators
Schwartz, Cédric ULg; Fedrigo, Tatiana ULg; Bruls, Olivier ULg et al

Poster (2011, July)

In human motion analysis, bone motions are usually expressed relatively to anatomical reference frames. The anatomical reference frames are constructed thanks to the localization of bony landmarks during ... [more ▼]

In human motion analysis, bone motions are usually expressed relatively to anatomical reference frames. The anatomical reference frames are constructed thanks to the localization of bony landmarks during a static phase prior to the acquisitions. These landmarks are identified by means of palpation. Accurate comparison between subjects and studies implies good reproducibility and repeatability of the palpation process. However, all investigators don’t have a long experience in palpation. In this paper, the reproducibility and repeatability of palpation for junior investigators were measured. Results show worse reproducibility and repeatability than what is usually expected. These errors have particularly an influence on the definition of the reference frames of the arm. This study therefore emphasizes on the need of a specific training of operators working in a motion lab. [less ▲]

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See detailImproving 3D measurements accuracy with camera information redundancy
Schwartz, Cédric ULg; Fringuellini, Anthony ULg; Bruls, Olivier ULg et al

Conference (2011, July)

The accuracy of the Codamotion system for 3D measurement depends mainly on the signal level of the sensors and the resolution of the system at the marker localization. When using several units to cover a ... [more ▼]

The accuracy of the Codamotion system for 3D measurement depends mainly on the signal level of the sensors and the resolution of the system at the marker localization. When using several units to cover a large field of view, the estimated position of the different units might differ. We propose a method taking both resolution and signal level in to account, instead of only the signal level as in the built-in weighting process. This new method offers improved accuracy. [less ▲]

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See detailEvaluation of the use of VEGF111 for the treatment of tendon lesions.
Janssen, Lauriane ULg; Kaux, Jean-François ULg; Drion, Pierre ULg et al

Poster (2011, May 20)

Alterations of tendons are common pathologies resulting from repetitive or abnormal mechanical sollicitations. Very frequently lesions become chronic and may even lead to rupture. As there is no current ... [more ▼]

Alterations of tendons are common pathologies resulting from repetitive or abnormal mechanical sollicitations. Very frequently lesions become chronic and may even lead to rupture. As there is no current efficient treatment for curing this type of diseases, new therapeutic approaches are being tested and developed. Injection of platelet-rich plasma (PRP) seems to be a promising treatment by local release of growth factors. Among these factors, VEGF-A is known to induce positive effects on vascular functions and angiogenesis, and could be implicated in the healing process of tendons. Several isoforms of VEGF-A have been described in literature, including VEGF165 and 121. VEGF111 is encoded by exons 1-4 and 8a. The lack of exon 5 enables VEGF111 to resist to proteolytic degradation and the absence of exons 6 and 7 reduces its affinity for several macromolecules present on the cell surface and in the extracellular matrix. In vivo, it has been shown to be highly proangiogenic and diffusible. A 5mm defect was surgically performed in the Achilles tendon of 60 rats. Two hours after closure of the fascia and the skin, an injection within the wound was performed with PBS alone (n=30) or with PBS containing 100 ng of VEGF111 (n=30). 10 rats of each group were sacrificed at days 5, 15 and 30. The operated tendon was then carefully removed and collected for either immunohistochemical analyses or mechanical testing. At each time point, the section and the overall appearance of the repairing tendons were similar for PBS and VEGF111-injected tendon. As compared to controls, injection of VEGF111 seemed to promote a faster angiogenesis, although the number of samples was at this stage too low for performing reliable statistical analysis. Mechanical resistance to rupture of the repairing tendons was also measured. No difference between the two groups was observed after 5 or 15 days. By contrast, increased tensile strength was clearly evidenced in the VEGF-treated group after 30 days. These preliminary data seem to indicate a positive effect of a single VEGF111 injection for restoring the mechanical properties of tendons after their section. Additional experiments are planned for confirmation purposes and for further characterizing the model. It includes a “dose- response” analysis, the use of VEGF165 as an additional control and a study evaluating the effect of several injections. [less ▲]

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See detailSensitivity of Structural Response to Wind Turbulence Characteristics
Denoël, Vincent ULg

in Marcuso, Russell J. (Ed.) Turbulence: Theory, Types and Simulation - Series: Physics Research and Technology (2011)

Civil engineering structures that are built in the atmospheric boundary layer have to be designed according to the gusty winds they are likely to withstand during their lifetime. Traditionally statistical ... [more ▼]

Civil engineering structures that are built in the atmospheric boundary layer have to be designed according to the gusty winds they are likely to withstand during their lifetime. Traditionally statistical characteristics of the wind turbulence -as standard deviation of and correlation between turbulence components, frequency content, etc. - are provided to structural engineers by meteorologists. The first dialogue between these two communities dates back to 1960's when they agreed on a list of necessary statistical characteristics of turbulence that need to be observed and measured to feed the structural models available at that time. In the framework of advanced wind loading models developed recently, it turns out that this basic list of statistical characteristics of turbulence is no longer sufficient. In this chapter, we point out some quantities that would need to be measured and others that are already measured but require a more precise estimation. This need is justified by analyzing the sensitivity, to these quantities, of the structural response to an advanced Wind loading model. After having introduced the need for advanced modeling of the wind loading, and eventually thus of the wind turbulence, a nonlinear non-Gaussian quasi-steady loading model is presented. Then the model is rigorously analyzed with cumbersome mathematics and statistics, with the permanent background aim at estimation of the influence of the turbulence properties. Final results are however presented in a concise way in order to pave the way for the future dialogue between engineers and meteorologists, and so build up the advanced design procedures that will presumably be used during the coming decades. [less ▲]

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See detailOptimal processing of wind tunnel measurements in view of stochastic structural design of large flexible structures
Blaise, Nicolas ULg; Denoël, Vincent ULg

in Lerner, J. C.; Boldes, U. (Eds.) Wind Tunnels and Experimental Fluid Dynamics Research (2011)

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See detailTransient Fokker-Planck Equation solved with SPH
Canor, Thomas ULg; Denoël, Vincent ULg

in Proceedings of the 5th International Conference on Advanced Computational Methods in Engineering (2011)

In many engineering matters, systems are submitted to random excitations. Probabilistic theories aim at describing the properties of a system by means of statistical properties such as probability density ... [more ▼]

In many engineering matters, systems are submitted to random excitations. Probabilistic theories aim at describing the properties of a system by means of statistical properties such as probability density function (pdf). For a deterministic system randomly excited, the evolution of its pdf is commonly described with Fokker-Planck-Kolmogorov equation (FPK). The FPK equation is a conservation equation of a hypothetical fluid, which represents physically the transport of probability. To solve this equation, Smoothed Particle Hydrodynamics (SPH) are used: the system is modelled with a conservation equation for the system and a transport equation for each particle. Numerical implementation shows the superiority of this method over many other mesh-based methods: (i) the conservation of total probability in the state space is explicitly written, (ii) no specific boundary conditions must be imposed if an adaptive smoothing length is chosen and if particles are initially regularly spread out, (iii) the positivity of the pdf is ensured. Furthermore, thanks to the moving particles, this method is adapted for a large kind of initial conditions (quasi-deterministic or even discontinuous). The FPK equation can be solved without any a priori knowledge of the stationary distribution; just a precise representation of the initial distribution is required. [less ▲]

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See detailEulerian Formulation of a Drillstring Constrained inside a Curved Borehole
Denoël, Vincent ULg; Detournay, Emmanuel

Conference (2011)

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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 ▲]

Detailed reference viewed: 28 (7 ULg)