Publication: An element dependent multiple lag rational function approximation for aeroelastic analysis of cable bridge

Date
2022-05-01
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Abstract
Modeling of self-excited aerodynamic forces using the rational function approximation (RFA) is studied. The Scanlan and Tomko model of self-excited forces contain flutter derivatives (FDs) that are function of reduced frequency. Various form of RFAs have so far been proposed to approximate the FDs of flat plate and bluff body deck sections. Herein an element dependent multiple lag (EDML) RFA is considered as an extension of Rogers RFA. This uses different lag coefficients for each element of the aerodynamic force coefficients. The state-space formulation in modal coordinates, using EDML RFA, is developed and applied to a long span cable-stayed bridge for flutter analysis. The formulation uses the basic idea that aerodynamic states involve convolutions arising from partial fractions of the RFA. The finite element model of the bridge is developed, and a geometrically nonlinear static analysis is performed, and mass and stiffness matrices extracted. EDML RFA yields the best fit for all FDs, although certain spikes and fluctuations are observed for some FDs. A marginal decrease in flutter speed is obtained. However, as the proposed EDML RFA based state-space formulation accurately predict FDs, it can be used for bluff body bridge decks with added features like crash barriers that may result in significant change in flutter speed.
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Keywords
Cable-stayed bridge | Flutter | Rational function approximation