RETROFIT EFFECT OF SFRC OVERLAY ON FATIGUE DURABILITY OF ORTHOTROPIC STEEL DECKS WITH CRACKS EXTENDING TO DECK PLATE

Abstract

 Since around 2000, a lot of fatigue cracks propagating into deck plate have been detected in existing orthotropic steel deck (OSD) bridges. The cause of the cracks is mainly due to out-of-plane bending of 12mm thickness deck plate. As an effective measure against those cracks, steel-fiber reinforced concrete (SFRC) overlays have been used for many existing damaged OSDs. It has been confirmed that they can drastically decrease the out-of-plane deformation of the deck plate and greatly reduce the local stress of the weld route portion where the cracks initiate. However, the effect of the SFRC overlay under the existence of deck crack inside the deck plate has not been clarified. In this paper, for the purpose of evaluating the retrofit performance under existing deck cracks, fatigue tests of the OSD specimens with pre-cracking inside the deck plates were carried out under SFRC overlay. Also, local stresses and stress intensity factors were analyzed by FEA, and effectiveness of SFRC overlay was assessed from the viewpoint of preventing the deck cracks from progressing.