Fatigue due to Traffic Loads and Different Approaches of Stress Calculations: Case Study of a Steel-Concrete Composite Bridge

Composite road bridges are usually subjected to dynamic actions and depending on the intensity and cycles of these actions this may compromise the structural system response reliability that could also lead to a reduction of the expected bridge service life. The fatigue due to traffic loads and stress on the structural system of a steel-concrete composite bridge is studied in this paper. Firstly, a theoretical evaluation was made following Eurocode and AASHTO norms for nominal stress calculation. The bridge 3D model was then developed using CSi Bridge software by Finite Element Analysis for moment history evaluation and calibrated by hand calculations using influence lines. Furthermore, Wöhler’s curves were used to evaluate the fatigue resistance of critical details such as the butt weld, weld with cope hole and vertical stiffeners for demand-capacity evaluations following registered traffic (cycle loads) on the one span steel-concrete composite bridge. The damage accumulation method was used to calculate cumulated damage on critical details following Eurocodes. Following AASHTO, maximum stress was calculated from equivalent stress, the result of refined analysis using truck survey variable amplitude stress ranges at critical detail position. The maximum stress was compared to the constant amplitude fatigue threshold for infinite life evaluation. Finally, the remaining life of the bridge structural system was predicted following Eurocodes and AASHTO.