A parametric study and rating of steel I-girder bridges subjected to military load classification trucks

This paper presents the flexural behavior and corresponding load rating of simply-supported steel I-girder bridges subjected to military truck loads. The military trucks are categorized by the Military Load Classification (MLC) system according to the North Atlantic Treaty Organization (NATO). A total of 144 load cases are studied for 6 different bridge models based on validated 3-dimensional finite element analysis (FEA) models to examine the deflection, lateral load distribution, and load rating of the bridges. The parameters examined include bridge characteristics (span length, girder spacing, and girder stiffness) and vehicular properties (wheel-line spacing, number of axles, and weight). The response of the bridges under the MLC trucks is compared with that under the standard HS20 trucks of the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO LRFD) specifications. Existing predictive models for load distribution factors are evaluated, including the applicability of bridge code provisions for the MLC trucks. The load rating methods based on the Load Factor Rating (LFR) and the Load and Resistance Factor Rating (LRFR) are studied.