Multi-mode Aerodynamic Analysis of Long-Span Bridges

Multi-mode responses to wind excitation have been estimated in the past by considering the response of each mode and then taking the root-sum-square for the total response. Other procedures, mainly in the time domain also exist but they have certain simplifying assumptions and limitations which disable the complete analysis of the systems as well as the estimation of the certain important criteria, e.g., flutter speed. A more comprehensive procedure is under development which will aim to capture the full bridge aerodynamics by considering simultaneously the effect of more than one mode. Frequency-domain functions (flutter derivatives) are preferred by most bridge dynamicists because they are easier to obtain experimentally. In this paper, the fundamental single-mode frequency-domain formulation is extended into the multi-modal domain.