Abstract
The fatigue phenomenon, which is caused from accumulation of live load stress, is one of the main factors controlling thelife of the steel bridge. In recent, increasing of the serviced year of the steel bridge and that of vehicle weight make thephenomenon as a primary concern to them. Korean code on the highway bridge design does not specify the detailed items suchas design load, loading method and impact factor for fatigue. Therefore, fatigue design of the steel bridge is done as the samemanner as the ordinary static design. By the way, if we think about design impact factor, the factor had been decided underwe use the same impact factor for fatigue design, it can lead to over-design in terms of fatigue. In this paper, appropriate impactfactor for fatigue design wil be discussed from the parametric study on the dynamic behavior of the steel girder bridge. Theparameters considered in this paper are bridge stifness, vehicle model, traffic flow, and road surface roughness of bridge etc.