Complex flutter-mode analysis for coupled gust response of the Akashi Kaikyo Bridge model

An analytical approach for the coupled gust response of long-span bridges is presented. The calculation scheme is based on the direct complex eigen-analysis of the integrated system of the three-dimensional FEM model of a long-span bridge and the aeroelastic forces. Actual vibration modes of the bridge in wind flow, which were so-called Complex-flutter Modes, are appropriately determined at each mean wind speed. A complex modal analysis scheme is then formulated for the gust response analysis in either time or frequency domains. By using the complex flutter-modes, the aeroelastic coupled gust responses are effectively captured and interpreted. A numerical example is made for the Akashi Kaikyo Bridge model. The calculated results agree very well with the experimental ones. Effects by the uses of spatial coherence, turbulent spectra, and some other factors on the gust response are then addressed.