References of "Denoël, Vincent"
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See detailAdjusted Equivalent Static Wind Loads for non-Gaussian linear static analysis
Blaise, Nicolas ULg; Denoël, Vincent ULg

Conference (2015, June)

In this paper, we propose a parametric bi-cubic model for the joint probability distribution of wind aerodynamic pressures and structural responses. This non-Gaussian model is a bivariate extension of the ... [more ▼]

In this paper, we propose a parametric bi-cubic model for the joint probability distribution of wind aerodynamic pressures and structural responses. This non-Gaussian model is a bivariate extension of the well-known Hermite polynomial transformation. It offers a new way to determine Equivalent Static Wind Loads, with the embedded feature to –at least partly– capture the non-Gaussianity of the aerodynamic pressures and responses. In a second step, based on the observation that this model as well as the usual LRC method or the conditional sampling technique, fail in reproducing structural responses that do not overestimate the extreme values resulting from a complete structural analysis, we propose a two-step adjustment procedure that restores the non-overestimation condition and the recovery of the considered structural response. With the example of a boundary layer flow around a duo-pitched roof, it is demonstrated that the Equivalent Static Wind Loads, adjusted or not, obtained with the proposed model of non-Gaussian joint probability density function reconstruct the envelope of structural response more efficiently than with the other two techniques. [less ▲]

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See detailRocking behaviour of simple unreinforced load-bearing masonry walls including soundproofing rubber layers
Mordant, Christophe ULg; Denoël, Vincent ULg; Degée, Hervé

in Proceedings of 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (2015, May)

This paper compares experimental measurements with predictions of different rocking models. These comparisons are carried out on the base of recent experimental results obtained by shake-table tests of ... [more ▼]

This paper compares experimental measurements with predictions of different rocking models. These comparisons are carried out on the base of recent experimental results obtained by shake-table tests of four simple unreinforced load-bearing clay masonry walls that have exhibited a significant rocking behaviour for the highest acceleration inputs. In a first stage, the simple model proposed by Housner is used after slight modifications needed to properly consider the actual mass distribution. Two parameters are identified as governing the model response, namely the criterion defining the initiation of motion and the restitution coefficient. Then, a two stacked blocks model is developed and solved by an event-driven strategy. This two-block model is intended to allow a better description of the behaviour of tested specimens through a more precise modelling of the additional mass. Finally, the pres-ence of rubber layers positioned at the top and bottom of two of the tested walls with the pur-pose of improving their acoustic behaviour required the development of an updated rocking model with viscous and flexible interfaces at the base of the wall and between the two stacked blocks. The properties of these interfaces are deduced from experimental data and their sig-nificant influence on the response is evidenced. [less ▲]

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See detailResearch Self-Evaluation Report of the Department ArGEnCo
Collin, Frédéric ULg; Dewals, Benjamin ULg; Elsen, Catherine ULg et al

Report (2015)

Evaluation is nowadays a general trend in the European Universities. At the University of Liège, the evaluation process is threefold: fist there is the evaluation of the bachelor and master degrees, then ... [more ▼]

Evaluation is nowadays a general trend in the European Universities. At the University of Liège, the evaluation process is threefold: fist there is the evaluation of the bachelor and master degrees, then the second evaluation concerns the internal administrations and finally Research activities are being evaluated. This quality policy at the different levels of the Institution is organized by the Vice-Rector for Quality, Pr. Freddy Coignoul and the SMAQ service (Service de Management et d’Accompagnement à la Qualité), which aims to promote, coordinate and disseminate within the University of Liège a culture of the Quality, founded on the values of the Institution. The Research assessment is a procedure undertaken by the University in order to promote the quality of the research in the Departments or research centres. Within the Faculty of Applied Sciences, the evaluation of the Bachelor and Master degrees in Engineering was carried out in 2013 by the AEQES (Agence pour l’Evaluation de la Qualité de l’Enseignement) and CTI (Commission des Titres d’Ingénieur - France). The present report is dedicated to the evaluation of research led in the Education and Research Department (DER) ArGEnCo. The present evaluation report proposes a global presentation of all our research activities. At the Department level, one of the elected members of the Executive Bureau is in charge of the Research, covering both evaluation and quality policy. In October 2013, the Executive bureau appointed a research steering committee, whose fist task was to coordinate the present evaluation report, following the guidelines of the SMAQ service. The draft of such a document arises from the work of the steering committee but also from the contributions of all Department members, who were asked to contribute to the report or to complete databases. The progress of this evaluation report was presented by the Steering committee to the Department Council and during the General Assembly of the Department. Moreover, two Focus groups were organized by the SMAQ service, in order to get the feedback of technician and administrative members on one hand and scientific members on the other hand, on the general organization of the research in the ArGEnCo Department. The reports of these two Focus groups (Appendix 4 in French) underpinned our thinking about our research management. This report is therefore the fist evaluation of the research led in the Department, the present effort should be pursued, and deepened, within the coming years. Some of the databases necessary for the evaluation have been developed in the frame of this procedure. This has resulted in a huge amount of work for every Department members to collect all the data. New procedures in the management of the Department will help establishing the next research evaluation reports systematically, in particular for the collection of the complete dataset. Following the guidelines of the SMAQ service, this evaluation report is divided into two main parts: the fist one focuses on a self-evaluation report of the research activities and the second part presents the Action Plan of the Department for the next five years to come. The self-evaluation report is composed of four Sections: Section one presents the Research organization and topics of the Department, Section two focuses on the Research activities, Section three gives an overview of the mobility (in and out), the attractiveness and the scientific recognition of the Department and finally Section four is dedicated to the resources available in ArGEnCo Department. Each Section ends up with a SWOT analysis. The Action Plan proposed by the Steering Committee results from the analysis of the self-evaluation report, insofar as it synthesizes and prioritizes the actions of the Department for the next fie years. These priorities are formulated as proposals following a contractual approach between research entities and Institution authorities, to whom the report will be presented. [less ▲]

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See detailAnalytical procedure to derive P-I diagram of a beam under explosion
Hamra, Lotfi ULg; Demonceau, Jean-François ULg; Denoël, Vincent ULg

in Proceeding of the IABSE Workshop - Safety, Robustness and Condition Assessments of Structures (2015, February)

The aim of this paper is to study a beam extracted from a frame and subjected to blast loading. The demand of ductility depends on six dimensionless parameters: two related to the blast loading, two ... [more ▼]

The aim of this paper is to study a beam extracted from a frame and subjected to blast loading. The demand of ductility depends on six dimensionless parameters: two related to the blast loading, two referring to the bending behaviour of the beam and two corresponding to the dynamic behaviour of the rest of the structure. We develop a full analytical procedure that provides the ductility demand as a function of these six dimensionless parameters. [less ▲]

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See detailDevelopment and validation of an accelerometer-based method for quantifying gait events
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Stamatakis, Julien et al

in Medical Engineering & Physics (2015)

An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO ... [more ▼]

An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO), and toe-off (TO), from wireless accelerometers applied to the right and left foot. First, the signals recorded from heel and toe three-axis accelerometers are segmented providing heel and toe flat phases. Then, the four gait events are defined from these flat phases. The accelerometer-based event identification was validated in seven healthy volunteers and a total of 247 trials against reference data provided by a force plate, a kinematic 3D analysis system, and video camera. HS, TS, HO, and TO were detected with a temporal accuracy ± precision of 1.3 ms ± 7.2 ms, ‒4.2 ms ± 10.9 ms, ‒3.7 ms ± 14.5 ms, and ‒1.8 ms ± 11.8 ms, respectively, with the associated 95% confidence intervals ranging from ‒6.3 ms to 2.2 ms. It is concluded that the developed accelerometer-based method can accurately and precisely detect HS, TS, HO, and TO, and could thus be used for the ambulatory monitoring of gait features computed from these events when measured concurrently in both feet. [less ▲]

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See detailConstrained Buckling of a Plane Elastica Inside a Frictional Conduit
Liakou, Anna; Denoël, Vincent ULg; Detournay, Emmanuel

Conference (2015)

Detailed reference viewed: 11 (1 ULg)
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See detailSegmentation of gait cycles using foot-mounted 3D accelerometers
Boutaayamou, Mohamed ULg; Bruls, Olivier ULg; Denoël, Vincent ULg et al

in Proceedings of the IEEE International Conference on 3D Imaging 2015 (2015)

We describe a new gait segmentation method based on the continuous wavelet transform to identify stride-by-stride gait cycles from measurements of foot-mounted three-dimensional (3D) accelerometers. The ... [more ▼]

We describe a new gait segmentation method based on the continuous wavelet transform to identify stride-by-stride gait cycles from measurements of foot-mounted three-dimensional (3D) accelerometers. The detection of such gait cycles is indeed a crucial step for an accurate extraction of relevant gait events such as heel strike, toe strike, heel-off, and toe-off. We demonstrate the ability of this segmentation method, used in conjunction with a validated extraction algorithm, to calculate the following gait (duration) parameters for each gait cycle during the gait of a healthy young subject and of an elderly subject with Parkinson’s disease (PD) in OFF and ON states: durations of (1) loading response, (2) mid-stance, (3) push-off, (4) stance, (5) swing, (6) stride, (7) step, and (8) double support phases. The experimental results show that the proposed method can extract relevant refined gait parameters to quantify subtle gait disturbances in subjects with PD. [less ▲]

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See detailDE3: Yet another high-order integration scheme for linear structural dynamics
Depouhon, Alexandre; Detournay, Emmanuel; Denoël, Vincent ULg

in Proceedings of the 5th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering. (2015)

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See detailResponse of an oscillator to a random quadratic velocity-feedback loading
Denoël, Vincent ULg; Carassale, Luigi

in Journal of Wind Engineering and Industrial Aerodynamics (2015), 147

Abstract The aerodynamic force acting on compact structures is often modeled as a quadratic function of the wind velocity, which fluctuates randomly due to the atmospheric turbulence. When a flexible ... [more ▼]

Abstract The aerodynamic force acting on compact structures is often modeled as a quadratic function of the wind velocity, which fluctuates randomly due to the atmospheric turbulence. When a flexible structure is considered and the quasi-steady assumption is applied, the wind velocity is substituted by the wind-structure relative velocity and, even in case of linear structures, the composite aerodynamic-mechanical system is governed by a nonlinear differential equation characterized by a quadratic feedback term. This class of dynamical systems has been deeply investigated (with different levels of simplifications) applying several alternative mathematical approaches. In this paper we define a system approximation based on a 2nd-order Volterra series and obtain its statistical response in terms of cumulants. The response cumulants are calculated applying the Multiple Timescale Spectral Analysis leading to analytic or semi-analytic expressions. All the approximations are validated through Monte Carlo simulation within a wide parameter space. Then, the analytical structure of the obtained expressions is used to discuss, from a qualitative point of view, the behavior of the considered dynamical system. [less ▲]

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See detailNumerical simulation of percussive drilling
Depouhon, Alexandre; Denoël, Vincent ULg; Detournay, Emmanuel

in International Journal for Numerical and Analytical Methods in Geomechanics (2015), 39(8), 889-912

This paper presents a novel dynamical model to analyze the long-term response of a percussive drilling system. This departs from existing approaches that usually consider a single activation and bit/rock ... [more ▼]

This paper presents a novel dynamical model to analyze the long-term response of a percussive drilling system. This departs from existing approaches that usually consider a single activation and bit/rock interaction cycle for the analysis of the process performance. The proposed model integrates the axial dynamics of an elastic piston and an elastic drill bit, a motion-dependent pressure law to drive the piston, and a generalized bit/rock interaction law representative of the dynamic indentation taking place at the bit/rock interface. It applies to down-the-hole percussive drilling as well as top-hole, with minor modifications. The model does not account for the angular motion or the hole cleaning, however. The model is first formulated mathematically; then, a finite-dimensional approximation is proposed for computations. Numerical analyses of the model response, for a low-size down-the-hole percussive system, follow. The period-1 stationary response for the reference configuration is studied in detail, and parametric analyses assessing the influence on the rate of penetration of the bit/rock interaction parameters, the feed force, and the percussive activation parameters are conducted. These analyses reveal that the multiscale nature of the process is well captured by the model and recover expected trends for the influence of the parameters. They also suggest that a significant increase of the penetration rate can be achieved by increasing the percussive frequency. Copyright © 2015 John Wiley & Sons, Ltd [less ▲]

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See detailAmbulatory system using wearable accelerometers for gait analysis in Parkinson’s disease
Boutaayamou, Mohamed ULg; Demonceau, Marie ULg; Schwartz, Cédric ULg et al

in Proceedings of the 14th Belgian Day on Biomedical Engineering (2015)

We describe a signal-processing algorithm for gait analysis in Parkinson’s disease (PD) using an ambulatory system with wearable accelerometers. This algorithm is versatile enough to detect, on a stride ... [more ▼]

We describe a signal-processing algorithm for gait analysis in Parkinson’s disease (PD) using an ambulatory system with wearable accelerometers. This algorithm is versatile enough to detect, on a stride-by-stride basis, refined gait parameters that quantify subtle gait disturbances in PD in a rater-independent way. [less ▲]

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See detailStabilité des Constructions
Denoël, Vincent ULg; Franssen, Jean-Marc ULg

Learning material (2015)

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See detailMultiple timescale spectral analysis
Denoël, Vincent ULg

in Probabilistic Engineering Mechanics (2015), 39(0), 69--86

Abstract Spectral analysis is a classical tool for the structural analysis of structures subjected to random excitations. The most common application of spectral analysis is the determination of the ... [more ▼]

Abstract Spectral analysis is a classical tool for the structural analysis of structures subjected to random excitations. The most common application of spectral analysis is the determination of the steady-state second order cumulant of a linear oscillator, under the action of a stationary loading prescribed by means of its power spectral density. There exists however a broad variety of such similar problems, extending the concept to multi degree-of-freedom systems, non Gaussian excitation, slightly nonlinear oscillators or even transient excitations. In this wide class of problems, the cumulants of the response are obtained as the result of the integral of corresponding spectra over the frequency space, which is possibly multidimensional. Application of standard numerical integration techniques may be prohibitive, a reason why the spectral approach is often left aside. Besides, many engineering problems involve a clear timescale separation, usually of those pertaining to the loading and to the mechanical behavior of the system. In these problems, a proper consideration of the timescale separation results in dropping the order of integration by one, at least. This offers the possibility to derive analytical solutions, whenever the order of integration drops to zero, or to make numerical integration competitive. The paper presents this general method, together with some applications in wind and marine engineering. [less ▲]

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See detailMonte Carlo Simulations of Autorotative Dynamics of a Simple Tower Crane Model
Vanvinckenroye, Hélène ULg; Denoël, Vincent ULg

in Proceedings of the 14th International Conference on Wind Engineering (2015)

The increasing number of crane accidents recorded over the last years might be understood as a need for progress on crane modeling. The induced risk of self-excited vibrations has already been ... [more ▼]

The increasing number of crane accidents recorded over the last years might be understood as a need for progress on crane modeling. The induced risk of self-excited vibrations has already been investigated through numerous experiments. This work presents a simple numerical model of a crane in a turbulent wind field, in order to support the available experimental approaches. First, the problem is defined with the necessary assumptions of the model. Second, the equation of motion is developed and wind characteristics are detailed. This equation presents several specificities requiring dedicated resolution methods. In a first analysis, the crane model is simplified in order to approach the behavior of the parametric pendulum and enable a general comparison of both responses. Indeed, the parametric pendulum is a well-known problem that is already widely described in the literature. In a second step, the response of the crane is studied under a realistic stochastic wind load with the full model. [less ▲]

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See detailApplication of random eigenvalue analysis to assess bridge flutter probability
Canor, Thomas; Caracoglia, Luca; Denoël, Vincent ULg

in Journal of Wind Engineering and Industrial Aerodynamics (2015), 140(0), 79--86

Abstract This study examines the well-known issue of evaluating the flutter probability for a long-span bridge, necessary for assessing structural integrity and reliability. The motivation stems from the ... [more ▼]

Abstract This study examines the well-known issue of evaluating the flutter probability for a long-span bridge, necessary for assessing structural integrity and reliability. The motivation stems from the need for critically reviewing and investigating a number of existing numerical approaches (e.g., random perturbation analysis, collocation methods, Galerkin approach) for the modeling and the solution of stochastic dynamic problems, by adapting them to the specific problem. The study proposes a generalized formulation for stochastic bridge flutter in terms of random eigenvalue analysis. A 1200 m suspension bridge model is used in the numerical simulations to compare the various methods and to provide indications on advantages and limitations of each method. Moreover, the link between the proposed formulation and existing studies on the propagation of uncertainty in aeroelastic systems, for example associated with measurement errors in wind tunnel, is examined. [less ▲]

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See detailMerging multi-camera data to reduce motion analysis instrumental errors using Kalman filters
Schwartz, Cédric ULg; Denoël, Vincent ULg; Forthomme, Bénédicte ULg et al

in Computer Methods in Biomechanics and Biomedical Engineering (2015), 18(9), 952-960

In motion capture systems, markers are often seen by multiple cameras. All cameras do not measure the position of the markers with the same reliability because of environmental factors such as the ... [more ▼]

In motion capture systems, markers are often seen by multiple cameras. All cameras do not measure the position of the markers with the same reliability because of environmental factors such as the position of the marker in the field of view or the light intensity received by the cameras. Kalman filters offer a general framework to take the reliability of the various cameras into account and consequently improve the estimation of the marker position. The proposed process can be applied to both passive and active systems. Several reliability models of the cameras are compared for the Codamotion active system, which is considered as a specific illustration. The proposed method significantly reduces the noise in the signal, especially at long range distances. Therefore, it improves the confidence of the positions at the limits of the field of view. [less ▲]

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See detailDevelopment and validation of a 3D kinematic-based method for determining gait events during overground walking
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Denoël, Vincent ULg et al

in IEEE International Conference on 3D Imaging (IC3D) (2014, December 09)

A new signal processing algorithm is developed for quantifying heel strike (HS) and toe-off (TO) event times solely from measured heel and toe coordinates during overground walking. It is based on a rough ... [more ▼]

A new signal processing algorithm is developed for quantifying heel strike (HS) and toe-off (TO) event times solely from measured heel and toe coordinates during overground walking. It is based on a rough estimation of relevant local 3D position signals. An original piecewise linear fitting method is applied to these local signals to accurately identify HS and TO times without the need of using arbitrary experimental coefficients. We validated the proposed method with nine healthy subjects and a total of 322 trials. The extracted temporal gait events were compared to reference data obtained from a force plate. HS and TO times were identified with a temporal accuracy ± precision of 0.3 ms ± 7.1 ms, and –2.8 ms ± 7.2 ms in comparison with reference data defined with a force threshold of 10 N. This algorithm improves the accuracy of the HS and TO detection. Furthermore, it can be used to perform stride-by-stride analysis during overground walking with only recorded heel and toe coordinates. [less ▲]

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See detailAn asymptotic expansion-based method for a spectral approach in equivalent statistical linearization
Canor, Thomas ULg; Blaise, Nicolas ULg; Denoël, Vincent ULg

in Probabilistic Engineering Mechanics (2014), 38

Equivalent linearization consists in replacing a nonlinear system with an equivalent linear one whose parameters are tuned with regard to the minimization of a suitable function. In particular, the ... [more ▼]

Equivalent linearization consists in replacing a nonlinear system with an equivalent linear one whose parameters are tuned with regard to the minimization of a suitable function. In particular, the Gaussian equivalent linearization expresses the properties of an equivalent linear system in terms of the mean vector and the covariance matrix of the responses, which are the unknowns of the optimization problem in a spectral approach. Even though the system has been linearized, the resulting set of equations is nonlinear. The computational effort in this method pertains to the solution of a possibly large set of nonlinear algebraic equations involving integrals and inversions of full matrices. This work proposes to develop and apply an asymptotic expansion-based method to facilitate and to improve the statistical linearization for large nonlinear structures. The proposed developments demonstrate that for slightly to moderately coupled nonlinear systems, the equivalent linearization can be applied with an appropriate modal approach and eventually seen as a convergent series initiated with the stochastic response of a main decoupled linear system. With this method, the computational effort is attractively reduced, the conditioning of the set of nonlinear algebraic equations is improved and inversion of full transfer matrices and repeated integrations are avoided. The paper gives a formal description of the method and illustrates its implementation and performances with the computation of stationary responses of nonlinear structures subject to coherent random excitation fields. [less ▲]

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See detailPressure-impulse diagram of a beam under explosion - Influence of the indirectly affected part
Hamra, Lotfi ULg; Demonceau, Jean-François ULg; Denoël, Vincent ULg

in Landolfo, Raffaele; Mazzolani, Frederico (Eds.) Proceeding of the 7th European conference on steel and composite structures (Eurosteel 2014) (2014, September 10)

The paper studies the structural response of a beam subjected to a close-field local internal blast loading. In the literature, the pressure-impulse (p-I) diagram is commonly used to design elements or ... [more ▼]

The paper studies the structural response of a beam subjected to a close-field local internal blast loading. In the literature, the pressure-impulse (p-I) diagram is commonly used to design elements or structures for a given blast loading. The p-I diagram is a spectrum representing the level sets of damage or required ductility for a given structural system, nonlinear beam in this paper. This representation is much appreciated because a simple reading for the actual pressure p and impulse I of the considered load indicates the ductility demand of the structural system. Recent works of quasi-static behaviour have indicated the crucial need to account for the membrane effects taking place in the extreme loading of frame beams. This paper will thus extend the state-of-art features, establishing thus the p-I diagram for a beam including the lateral restraints offered by the rest of the structure, the development of non-linear membrane action and also, the M-N interaction that develops in the plastic hinges. [less ▲]

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