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Wind and Structures
  Volume 16, Number 6, June 2013 , pages 561-577
DOI: https://doi.org/10.12989/was.2013.16.6.561
 


Extraction of rational functions by forced vibration method for time-domain analysis of long-span bridges
Bochao Cao and Partha P. Sarkar

 
Abstract
    Rational Functions are used to express the self-excited aerodynamic forces acting on a flexible structure for use in time-domain flutter analysis. The Rational Function Approximation (RFA) approach involves obtaining of these Rational Functions from the frequency-dependent flutter derivatives by using an approximation. In the past, an algorithm was developed to directly extract these Rational Functions from wind tunnel section model tests in free vibration. In this paper, an algorithm is presented for direct extraction of these Rational Functions from section model tests in forced vibration. The motivation for using forced-vibration method came from the potential use of these Rational Functions to predict aerodynamic loads and response of flexible structures at high wind speeds and in turbulent wind environment. Numerical tests were performed to verify the robustness and performance of the algorithm under different noise levels that are expected in wind tunnel data. Wind tunnel tests in one degree-of-freedom (vertical/torsional) forced vibration were performed on a streamlined bridge deck section model whose Rational Functions were compared with those obtained by free vibration for the same model.
 
Key Words
    flutter analysis; time-domain method; rational function approximation; forced vibration; long-span bridges
 
Address
Bochao Cao : 2271 Howe Hall, Department of Aerospace Engineering, Iowa State University, Ames, IA, 50011-2271, USA ; Department of Mechanics and Engineering Science, Fudan University, PR China
Partha P. Sarkar: 2271 Howe Hall, Department of Aerospace Engineering, Iowa State University, Ames, IA, 50011-2271, USA
 

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