This report is the second of a two-volume final report presenting the findings of the research work that was undertaken to evaluate the fatigue behavior of steel highway bridges on the extra heavy weight corridor in Northwest Indiana. The purpose of the study was to evaluate the type and magnitude of the loads that travel along the corridor and then assess the effect of those loads on the fatigue strength of the steel bridges on the corridor. This volume presents the results of an evaluation of the fatigue strength of steel bridge structures along the extra heavy weight corridor. A fatigue load model was developed based on a three-axle and four-axle fatigue truck to accurately represent the fatigue damage caused by the actual truck load history. A fatigue damage model was also developed using a statistical database of resistance parameters to assess the fatigue strength for a level of safety selected by the user. The utility of the model was evaluated through a field investigation of two different bridge structures. Strain data were collected for more than three weeks at both sites. The behavior predicted by two-dimensional and three-dimensional analytical bridge models were compared with measured strain data. It was found that both the 1D and 3D models provided conservative fatigue life estimates, although the 3D model was considerably closer to the measured strain behavior. The fatigue truck along with the fatigue damage model was then used to assess thirteen steel bridge structures along the corridor. A remaining fatigue life of more than 25 years was found for the critical details for all bridges using the most conservative 1D model. Most remaining fatigue lives, however, were considerably longer than 25 years.

Report Number



fatigue, bridge, steel, girder, heavy truck, Michigan train truck, weigh-in-motion, strain measurements, remaining life, SPR-2385

SPR Number


Publisher Place

West Lafayette, IN

Date of this Version