Development of improved natural frequency equations for continuous span steel I-girder bridges

Field testing and analytical studies to predict natural frequencies of steel stringer bridges are reviewed in this paper. A three-dimensional (3D) finite element analysis (FEA) procedure using the commercial software ABAQUS, which efficiently captures the vibration characteristics of such bridges, is proposed. Two continuous-span composite steel bridges dynamically (field) tested by others were used to validate the proposed FEA model, which indicates excellent agreement between the analytical and field data. A natural frequency parametric study has been conducted by utilizing the FEA procedure. Based on the regression analysis of the parametric study results, practical equations are proposed to predict the natural frequencies of continuous-span composite steel bridges. The parametric study results are also compared with existing prediction methods, showing that the proposed equations represent a significant improvement over the existing prediction methods.