Aerodynamic admittance and the `strip theory’ for horizontal buffeting forces on a bridge deck

Abstract

In wind tunnel tests of bridges for buffeting arising from fluctuating wind velocity, one of the items requiring attention is how to simulate the natural wind characteristics of the construction region. In wind tunnel tests of long-span cable-stayed bridges under construction, when two types of turbulent boundary layer with different wind characteristics were used, there was a tendency for the match between the wind tunnel test values and buffeting analysis values to vary with the type of turbulent boundary layer. Horizontal buffeting was considered for which there are fewer previous examples than for vertical buffeting. As a result of pursuing the cause of the lack of matching, it was found that the aerodynamic admittance used in the analysis and the measured aerodynamic admittance were quite different. This difference arose from the fact that the correlation of the fluctuating velocity spanwise was smaller than the value assumed in the analysis. Also, according to past research, there are many examples in which strip theory according to which the fluctuating wind velocity correlation and the fluctuating aerodynamic correlation are equivalent is not valid. Here, it is also considered whether or not the strip theory is valid for horizontal buffeting.