The common approach for the prediction of bridge aeroelastic behaviour, and of flutter instability as its extreme consequence, consists in identifying sets of frequency dependent coefficients (aeroelastic derivatives) through wind tunnel tests on scaled-down cross-sectional models of the bridge deck. In order to allow the prediction of full-bridge behaviour, suitable numerical models are developed, which combine the aeroelastic properties of the cross-section with the dynamic properties of the full bridge obtained through finite element modelling. The most sophisticated methods in the frequency domain are the so-called multimodal approach [1], where some selected modes of the structures can contribute to the bridge response and to the flutter instability mode (which results then from a complex eigenvalue problem). An alternative approach is based on indicial functions [2, 3], i.e. the time-domain counterparts of aeroelastic derivatives. Indicial functions can be identified through experimental tests or by means of a numerical nonlinear optimization that uses experimental aeroelastic derivatives as input parameters. Time-domain simulations at increasing mean wind velocity can be performed and the critical condition is easily identified as the onset of diverging motion [4]. When the indicial functions are extracted from aeroelastic derivatives, the multimodal approach and the time-domain simulations are theoretically equivalent. Nevertheless, the numerical identification of indicial function introduces some approximation. Moreover, the apparently more complicate procedure throws some scepticism on the time-domain models, if compared with the well-established frequency-domain models. In this work, the equivalence of the frequency- and time- domain methods is verified through fullbridge study cases. Moreover, advantages and disadvantages of the two techniques are discussed.
Frequency- versus Time- Domain Methods for the Numerical Modelling of Bridge Aeroelasticity / C. Borri; L. Salvatori. - STAMPA. - (2007), pp. 1-1. (Intervento presentato al convegno 4th MIT Conference on Computational Mechanics tenutosi a Cambridge, MA, USA nel 13-15 giugno 2007).
Frequency- versus Time- Domain Methods for the Numerical Modelling of Bridge Aeroelasticity
BORRI, CLAUDIO;SALVATORI, LUCA
2007
Abstract
The common approach for the prediction of bridge aeroelastic behaviour, and of flutter instability as its extreme consequence, consists in identifying sets of frequency dependent coefficients (aeroelastic derivatives) through wind tunnel tests on scaled-down cross-sectional models of the bridge deck. In order to allow the prediction of full-bridge behaviour, suitable numerical models are developed, which combine the aeroelastic properties of the cross-section with the dynamic properties of the full bridge obtained through finite element modelling. The most sophisticated methods in the frequency domain are the so-called multimodal approach [1], where some selected modes of the structures can contribute to the bridge response and to the flutter instability mode (which results then from a complex eigenvalue problem). An alternative approach is based on indicial functions [2, 3], i.e. the time-domain counterparts of aeroelastic derivatives. Indicial functions can be identified through experimental tests or by means of a numerical nonlinear optimization that uses experimental aeroelastic derivatives as input parameters. Time-domain simulations at increasing mean wind velocity can be performed and the critical condition is easily identified as the onset of diverging motion [4]. When the indicial functions are extracted from aeroelastic derivatives, the multimodal approach and the time-domain simulations are theoretically equivalent. Nevertheless, the numerical identification of indicial function introduces some approximation. Moreover, the apparently more complicate procedure throws some scepticism on the time-domain models, if compared with the well-established frequency-domain models. In this work, the equivalence of the frequency- and time- domain methods is verified through fullbridge study cases. Moreover, advantages and disadvantages of the two techniques are discussed.File | Dimensione | Formato | |
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