Methodology for Impact Factor of Horizontally Curved Box Bridges

Abstract

This paper presents a method for determining the dynamic impact factor of horizontally curved steel box‐girder bridges under vehicle loadings. The two‐dimensional planar grid analogy is used to model box bridges. The vehicle is idealized as a pair of concentrated forces, with no mass, traveling, on circumferential paths with constant velocity. Analysis of multigirder and continuous span bridges indicates a tendency for frequency clustering. Static solutions for these bridges are compared against mode superposition and direct integration. The bridge behavior was studied under several truck loading paths. Static and dynamic bridge behavior was observed under these loadings. A rational methodology for determining the impact factor is developed, and alternate impact‐factor criteria are proposed to replace the current American Association of State Highway and Transportation Officials guide specification.