Abstract
Due to the increase of the amount of traffic and the weight of trucks, the fatigue cracks are occurring at the welding joints of steel bridges. This report shows the properties on the surface and depth direction of residual stress of welded joint specimens which were treated by hummer peening in order to study the effect of the hummer peening to the high-strength (HT780) and the conventional (SM490) steel. It was also clarified that the fatigue life of the high-strength steel welded joint specimens which were treated by hummer peening were more than twice as long as the untreated them.
