Evaluation of Damage Equivalent Factor for Roadway Bridges

The Eurocodes provide a simplified fatigue design control through the use of fatigue load model 3 (FLM3) and damage equivalent factor, λ, which is now widely used. In applying the Eurocodes method, the first problem arises when designers try to determine the corresponding fatigue span length, especially for bridge static systems not listed. Second problem is that in case of long bridges, the probability of having several trucks simultaneously over bridge exists (in single lane traffic as well as in multi-lane traffic); it results in larger cycles and, accordingly, higher contributions to total damage. This paper first evaluates the damage equivalent factors and then provides an all-inclusive method for determining the fatigue critical length for any bridge static system and the

corresponding damage equivalent factor. It proposes modifications for improving the fatigue design method using damage equivalent factors.