Frequency-Domain Approach for Calculating Wind-Induced Vibration...

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Frequency-Domain Approach for Calculating
Wind-Induced Vibration and Aeroelastic Stability Characteristics
of Long-Span Bridges

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Risto Kiviluoma: Frequency-Domain Approach for Calculating Wind-Induced Vibration and Aeroelastic Stability Characteristics of Long-Span Bridges

Doctoral dissertation at Helsinki University of Technology

The frequency-domain approach is applied to the aerodynamic and aeroelastic analysis of long-span bridges. Numerical models are deduced for the simultaneous buffeting and flutter analysis and for the vortex and signature turbulence induced response calculation.
The goal, considered to be achieved, is to develop numerical models capable to reliable parametric studies of detailed three-dimensional structural models of bridges. For the models, semi-empirical approach based on aerodynamic data obtained through section model tests in a wind tunnel, is employed. The data consists of the steady aerodynamic coefficients and flutter derivatives of a deck
segment to be used in the buffeting and flutter analysis. A complemental data is suggested to be extracted for the
vortex and signature turbulence induced response calculation.
The simultaneous analysis model for buffeting and flutter uses theoretically complete coupled-mode approach in which most of the unintentional simplifications of earlier models are removed. It has merits for the non-iterative calculation of flutter characteristics and feasibility to efficient computer implementation. The vortex-induced response calculation is based on the band-limited white-noise excitation model while the signature-turbulence model employs approach typical in simplified buffeting analysis of bridge girders. The
vortex-induced vibration calculation model facilitates imperfect spanwise correlation and turbulence reduction effects through mutually simple mathematical formulation. To obtain aerodynamic input parameters for the verification study, wind tunnel tests for the spring supported section model are carried out in a smooth flow. The Instrumental variable method is formulated for acceleration signals and used on evaluating flutter derivatives through coupled-motion experiments. To verify the numerical models, the calculated responses of the Raippaluoto and Kärkinen Bridges, two cable-stayed bridges in Finland involving double I-girder steel-concrete composite deck, are compared with the on-site measurements. Here, the responses and the wind turbulence data are measured on three occasions during storm and strong winds in 1999-2000.

Keywords:
aeroelasticity, vibration, cable-stayed bridges, buffeting, flutter, vortex shedding, turbulence, wind tunnel





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