용접결함을 가진 강교량의 피로수명 평가

Abstract

Recently, it has been reported that fatigue damage of steel bridge are occurred due to vehicles and traffic volumes. There may be attributed to the defets at the welded joints. In general, the fatigue crack in welded joints initiates from welded defects. In order to prevent fatigue damage, the estimation of fatigue life for the welded joints should be performed. The objective of this study is to investigate the effect of proportion vehicles on the fatigue crack propagation life according to vehicle speed. The basic theory for fatigue crack propagation based on the fracture mechanics is described and the estimation of fatigue crack propagation life is performed on welded defects occurred at the butt welded joints of diaphragm in a three span continuous steel box girder bridge. The stress variation analysis has been performed based on the Monte-Carlo simulation load. Equivalence stress range were determined to calculate a stress intensity factor range , then the fatigue crack propagation analysis has been carried out by applying the strength level to fillet welded joint of bottom flange . The edge cracks, though thickness crack and semi-elliptical surface crack were used for fatigue crack types. Based on the result, the fatigue crack propagation life depends on the proportion of vehicle and the vehicle speed. It is shown that fatigue crack propagation life decreased as the proportion of heavy vehicle increase and the vehicle speed in reduced. In case of a semi-elliptical surface crack occurred on the base metal