Indicial Aerodynamic Functions for Bridge Decks

With certain classical results for airfoils as a guide, lift and moment functions of the indicial type are derived for suspension bridge deck sections of either the open truss or streamlined variety. Bluff deck sections susceptible to coherent vortex shedding are not treated. The indicial functions are obtained analytically from the experimentally-derived linear-theory flutter derivatives of the bridge deck sections in question. The method used is nonlinear least squares, wherein a prescribed exponential form with unknown coefficients for the indicial function is determined by fitting transformed counterparts of it to the corresponding experimental flutter derivative curves. Several examples of indicial moment functions of bridge deck sections are presented. These offer rather conclusive proof that Wagner or thin airfoil theory alone is inadequate for application to bridge buffeting flutter and buffering analyses.