Prediction of Ultimate Strength Determined by Brittle Fracture Initiating from Weld Defects - Quality Control Criterion of the Connections

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K06595
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Building structures/Materials
• Research Institution: Sojo University
• Principal Investigator: AZUMA Koji 崇城大学, 工学部, 教授 (80320414)
• Co-Investigator(Kenkyū-buntansha): 岩下 勉 有明工業高等専門学校, 創造工学科, 教授 (10332090)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 脆性破壊 / 延性き裂 / 溶接欠陥 / 破壊靱性 / 塑性拘束 / 破壊評価 / 終局耐力 / スカラップ

Outline of Final Research Achievements

This paper concerns the applicability of the Weibull stress approach for prediction of brittle fracture initiated at the root of welds. Beam-to-diaphragm joint models, which were designed to represent a connection of beam-to-column joint with through diaphragms, were tested under cyclic loads. The load was applied to the end of the cantilever by a hydraulic ram cyclically. Specimens had those discontinuities at the roots of welds to the diaphragm. Through cracks were installed on both sides of weld terminations. The prediction of brittle fracture with a variety of defect sizes by using the FE analysis was conducted. The applicability of the Weibull stress approach, comparing it with the applicability of the TSM approach, in predicting brittle fracture from such defects was verified. Furthermore, the effect that the shape of weld access hole gives to ultimate strength of specimens was examined, because the brittle fracture occurred from the toes of weld access hole of some specimens.

Free Research Field

建築構造

Academic Significance and Societal Importance of the Research Achievements

造船や溶接の分野では古くから脆性破壊に関する研究が行われており，材料強度学として一つの体系をなしている．塑性変形能力に期待する耐震設計において，最も避けたい破壊形式であるが，近年，建築分野ではこの種の研究が減少している．兵庫県南部地震直後には，鋼構造建物の柱梁接合部における脆性破壊が注目され，数多くの防止策の検討がなされ，破壊評価手法が策定されたが，延性き裂の影響を考慮したものは未だに確立されていない．今後，予想される巨大地震が発生する前に，この点を解決した評価方法を確立することは，建物の安全性を担保する上で，大きな意義がある．