강교의 프리스트레스 도입에 따른 피로손상부에서의 보강 효과 평가

Abstract

Fatigue damage of bridge occurs through increase of traffic and weightness of common load. Fatigue damage occurs in locations of stress concentration such as weld zone of secondary member. This fatigue damage not only shortens life of bridge but also can be cause of bridge collapse. Therefore, bridge should be retrofitted through regular checking.

General retrofitting methods of bridge is continuation of simple bridge, joining steel sheet, addition of secondary member, and prestress method of construction. Prestress method can be divided into direct prestress method to introduce tendon and indirect prestress method to introduce tensible force through Up and Down of girder support. Direct prestress method suppresses deflection of bridge, and can reduce stress of girder that occurs through load. Indirect prestress method by Up and Down of support controls negative moment in internal support, so can improve behavior of continuous bridge.

However, a study on a retrofitting effect in fatigue damage part according to introduction of prestress was not proceeded. Therefore, this study evaluated a retrofitting effect in fatigue damage part according to introduction of direct prestress and indirect prestress through structural analysis.

Target bridgeⅠ is three-span continuous steel box girder bridge completed in 1981, so introduces tensible force by installing prestress strand in the side-span bottom that receives positive moment. Fatigue damage in target bridgeⅠ occurred in longitudinal rib and diaphragm weld zone. As a result to evaluate the effect according to direct prestress retrofitting, a retrofitting effect occurred in general deflection and stress of axis direction, but there was no reduction effect of sectional stress in part with fatigue damage.

Target bridgeⅡ is four-span continuous steel plate girder bridge retrofitted by indirect prestress method, so introduces prestress through Up and Down method in process to change one-span simple bridge into four-span continuation bridge. Fatigue damage in target bridgeⅡ occurred in weld connection of transverse stiffener and top flange. As a result to evaluate the effect according to indirect prestress retrofitting, a general retrofitting effect occurred, but there is no reduction effect of sectional stress in part with fatigue damage.

Therefore, there is no effect according to general retrofitting in part with fatigue damage, so direct retrofitting of fatigue damage part is needed.