Etienne Balmes

Merging Sensor Data from Multiple Temperature Scenarios for Vibration Monitoring of Civil Structures

The ambient temperature effect may result in limitations of vibration-based SHM approaches for civil engineering structures. This paper addresses the issue of discriminating changes in modal parameters due to damages and changes in modal parameters due to temperature effects. A nonparametric damage detection algorithm is proposed, which only assumes that several data sets are recorded on the safe structure at different and unknown temperatures, and smoothes out the temperature effect using an averaging operation.

Iterative Computation of Modal Sensitivities

The computation of frequency and mode shape sensitivities with respect to design parameters is essential to many, structural optimization and finite element updating algorithms. Approximating the gradients may lead to poor estimates and loss of convergence, but on the other hand the cost of exact methods, such as Nelsons (Nelson, R.,, Simplified Calculations of Eigenvector Derivatives, A1AA Journal, Vol. 14, No. 9,1976, pp. 1201-1205), is often not acceptable for industrial-size models. The present study thus analyses existing approximation methods, suggests a first-order improvement of Fox and Kapoors modal basis (Fox, R., and Kapoor, M., Rate of Change of Eigenvalues and Eigenvectors A1AA Journal, Vol. 6, No. 12, 1968, pp. 2426-242, 9) and proposes a residual iteration technique allowing accurate computations of modeshape sensitivities. An engine cover model and a model of the Ariane 5 main cryogenic stage are used to analyze, for models of realistic sizes, the accuracy and computational costs of the proposed methods.

Handling the Temperature Effect in Vibration Monitoring of Civil Structures: A Combined Subspace-Based and Nuisance Rejection Approach

Abstract: : Monitoring the vibrations of a structure has been recognized as a useful monitoring approach. However, the temperature and other environmental factors are known to affect the way a civil structure vibrates. A vibration monitoring method based on a subspace residual and χ2-type global and sensitivity tests has been proposed by some of the authors. In this paper, an extended detection algorithm is presented, which rejects the temperature effect viewed as a nuisance parameter. Its relevance when applied to a simulated bridge deck example is investigated.

Expansion par minimisation du résidu dynamique

Lexpansion par minimisation du résidu dynamique (MDRE) cherche à estimer la réponse de modes propres expérimentaux sur tous les Degrés De Liberté (DDLs) dun modèle éléments Finis (EF) en minimisant la somme pondérée dune erreur de modèle et dune erreur sur les mesures. On présente ici une méthode de résolution itérative de ce problème dexpansion, qui permet son application à des modèles de taille industrielle. La capacité des résidus dynamiques issus de lexpansion à localiser des erreurs est ensuite évaluée pour des expériences simulées avec des défauts connus, sur un modèle de couvre-culasse Renault comportant 16,840 DDLs.

Test/analysis comparison of piezoelectric patch local behavior for vibroacoustic active control application

To predict the effect of active control on aircraft or helicopter trim panels, made with honeycomb sandwich composite, one approach consists in modeling the panel by Finite Element Method. FEM with shell elements for the laminate and volume elements for the core is classically used in industry; in a previous study the homogenized modeling approach has been validated. The aim of the present paper is to make a test/analysis comparison of the dynamic behavior of a honeycomb core sandwich beam actuated by a piezoelectric patch. More precisely, the behavior in the vicinity of the piezoelectric actuator is characterized, in order to validate the modeling approach of honeycomb sandwich composite equipped with piezoelectric patches.

HANDLING THE TEMPERATURE EFFECT IN VIBRATION MONITORING OF CIVIL STRUCTURES: A COMBINED SUBSPACE-BASED AND NUISANCE REJECTION APPROACH 1

Abstract Monitoring the vibrations of a structure has been recognized as a useful monitoring approach. However, the temperature and other environmental factors are known to affect the way a civil structure vibrates. A vibration monitoring method based on a subspace residual and X 2 -type global and sensitivity tests has been proposed by some of the authors. In this paper, an extended detection algorithm is presented, which rejects the temperature effect viewed as a nuisance parameter. Its relevance when applied to a simulated bridge deck example is investigated.