Practical diagnostic method for fatigue cracks at main girder-cross beam connections in steel bridges

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K04237
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 22020:Structure engineering and earthquake engineering-related
• Research Institution: Tokyo Metropolitan University
• Principal Investigator: Murakoshi Jun 東京都立大学, 都市環境学部, 教授 (60355881)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 鋼桁橋 / 主桁－横桁接合部 / 疲労損傷 / 診断手法 / 疲労対策

Outline of Final Research Achievements

This study investigated practical diagnostic methods for fatigue cracks caused by secondary stresses at the main girder-cross beam connections in steel girder bridges through field measurements and numerical analysis. Finite element analysis using three-dimensional models of two bridges revealed that local stresses result from the deformation behavior of the entire bridge structure. The proposed deformation indices at crack focal points allow for the quantitative evaluation of local stress under various structural conditions. Additionally, countermeasures for fatigue damage were examined. The effects of various countermeasures to reduce local stress were clarified, focusing on suppressing deformation by increasing girder or deck rigidity and releasing restraints on local deformation.

Free Research Field

橋梁工学，鋼構造学

Academic Significance and Societal Importance of the Research Achievements

本研究では，き裂発生部位の二次応力と損傷要因とされる橋全体系の変形挙動との関係を定量的に明らかにするとともに，複数の応力軽減策の効果を評価しており，適切な対策工法選定のための有用な知見が得られている．今後，提示した変形指標を橋梁設計で適用される構造解析モデルにおける変形パラメータと関連付けることにより，局部応力を簡便に推定し疲労き裂の進展性を概略評価する方法に展開していくことが期待される．