Dimensionless Free Vibration Analysis of Suspension Bridges Considering Hanger Extensibility and Various Girder Types

In this paper, free vibration analyses with an improved continuum model for three-span suspension bridges are performed to study the effects of hanger extensibility on free vertical vibrations. The improved model can consider extensible hangers as well as various girder types such as hinged, continuous, and floating girders. To derive the equations of motion for this model, the coupled differential equations for the vertical deflections of the main cable and girder are presented. The Galerkin’s method with the shape functions for the main cable and girder is introduced into the differential equations, and it leads the equations to a matrix form. The natural frequencies of a three-span suspension bridge are evaluated from the equations with the six dimensionless parameters. In the parametric analyses, the effect of the hanger extensibility is observed.