강교의 고장력볼트 파단 원인 분석 및 안전관리 방안에 관한 연구

Abstract

High-strength bolts, which are widely used for connecting and joining members of steel bridges, can cause structural safety degradation of the bridge due to reduced strength of the connecting/joining part when defects or damage such as cracks/ruptures occur, and if the broken bolts fall to the bottom of the bridge, they can cause traffic accidents for vehicles passing underneath. Accordingly, the status of high-strength bolts is inspected during safety inspections/diagnoses of steel bridges. Meanwhile, in the safety inspection/diagnosis practice of steel bridges, a visual inspection of the status of high-strength bolts is performed, and a detailed inspection such as a non-destructive test is performed on bolts that are found to be abnormal during the visual inspection process. However, since this visual inspection method makes it difficult to directly check defects or damage occurring inside the high-strength bolts, even if there are bolts that are actually in a state of internal fracture, they may not be detected during the inspection process. Recently, during the safety diagnosis process of the ○○ Bridge in Busan, a fracture of an F13T bolt, which has not yet been reported in Korea, was discovered. This study aims to identify the cause of the failure of high-strength bolts in the ○○ Bridge in Busan and, based on this, to suggest safety management measures to prevent this type of failure in the future. To this end, we conducted an analysis of the broken bolts collected from the site, and additional on-site non-destructive testing was conducted on the bolts connected around the broken bolts to check whether there were any internally broken bolts. The results of the on-site non-destructive testing confirmed the existence of additional internally broken bolts that were not found during the visual inspection, and this confirmed the need for improvement in the method of checking the condition of high-strength bolts. In addition, the analysis of the existing broken bolts and the additionally discovered broken bolts, as well as the analysis of overseas cases, revealed that the cause of the failure of the ○○ Bridge bolts was delayed failure due to hydrogen embrittlement, and this confirmed the need for inspection to secure the safety of delayed failure of F13T high-strength bolts. The results of this study indicated that it is necessary to establish safety management improvement measures such as conducting non-destructive testing to prevent delayed failure of high-strength bolts in steel bridges.