Generalized framework for identification of indicial response functions from flutter derivatives of long-span bridges

The hypothesis that the Wagner and Kussner functions, conventionally used in the thin-airfoil aerodynamics, can also be used in the bridge aerodynamics, is often suggested in the literature. However, this assumption may lead to an inaccurate prediction of the buffeting response of bridges with increasing spans, which calls into question the validity of this assumption. This paper presents a generalized framework for the identification of bridgerelated aerodynamic and aeroelastic indicial response functions (IndRFs) to simulate the buffeting response of long-span bridges under turbulent winds. For that, the direct relationships between IndRFs and experimental data of flutter derivatives are developed with the help of the Fourier transform, followed by the extraction of IndRFs through an optimization technique. Compared with the conventional Wagner and Kussner functions, the identified IndRFs exhibit the overshooting behavior, which can change the bridge aerodynamics significantly. To check the efficacy of the proposed framework, the numerical example of a suspension bridge is presented, and buffeting analysis is performed for two cases considering (1) the identified aeroelastic and aerodynamic IndRFs, and (2) the Wagner and Kussner functions. The simulation results are also compared with the field measurements, showing that the identified IndRFs are adequately reliable and unique functions for a bridge deck to simulate its buffeting response accurately.