Fatigue Evaluation of a Strengthened Steel Truss Bridge

Many existing steel bridges in China were strengthened or retrofitted recently to improve the load-carrying capacity or to extend the service life span. The effectiveness of these measures is investigated by evaluation of fatigue life of a strengthened highway continuous steel truss bridge in order to ensure continued safe use and to gain knowledge on repair or replacement. Three-dimensional finite element models of the structure before and after strengthening are established through calibration with in situ measured stresses and displacement. The traffic condition of the bridge is investigated, and the stress histogram and stress spectrum are simulated by the Monte Carlo method. The fatigue life and damage of all fracture-critical tension members before and after strengthening of the structure is calculated using S-N curves and by adopting a fracture mechanics model. Finally, the effectiveness of the strengthening is evaluated and a maintenance strategy evolved on the basis of the results of evaluation.