Grant-in-Aid for Scientific Research (A)
|Allocation Type||Single-year Grants|
|Research Institution||Kyoto University|
NAKASHIMA Masayoshi Kyoto University, Disaster Prevention Research Institute, Assoc.Prof., 防災研究所, 助教授 (00207771)
INOUE Kazuo Kyoto University, Graduate School of Engineering, Prof., 大学院・工学研究科, 教授 (40029294)
SUZUKI Yoshiyuki Kyoto University, Disaster Prevention Research Institute, Assoc.Prof., 防災研究所, 助教授 (50027281)
NONAKA Taijiro Kyoto University, Disaster Prevention Research Institute, Prof., 防災研究所, 教授 (60027224)
岩井 哲 京都大学, 防災研究所, 助手 (60184850)
藤原 悌三 京都大学, 防災研究所, 教授 (10026031)
|Project Period (FY)
1996 – 1998
Completed(Fiscal Year 1998)
|Budget Amount *help
¥11,800,000 (Direct Cost : ¥11,800,000)
Fiscal Year 1998 : ¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1997 : ¥4,000,000 (Direct Cost : ¥4,000,000)
Fiscal Year 1996 : ¥6,000,000 (Direct Cost : ¥6,000,000)
|Keywords||Steel Frame / Beam-to-Column Connection / Welding / Brittle Fracture / Loading Rate / Temperature / 兵庫県南部地震 / 柱はり仕口 / 塑性変形能力 / ひずみ速度 / スカラップ|
The objective of this research is to identify the reasons why so many welded beam-to-column connections fractured in the 1994 Northridge and 1995 Hyogoken-Nanbu Earthquakes. The focuses of the investigation are the welding method, loading rate, and loading sequence, and a study comprising the following steps was carried out : (1) collection of previous test data and development of database on welded beam-to-column connections ; (2) survey of damage patterns exhibited in the previous earthquakes ; (3) tests of beam-to-column connections with the welding method, loading rate, and loading sequence as parameters ; and (4) synthesis of obtained results and proposals for new design procedures. The major findings are summarized as follows :
(a) A database that contains previous tests of welded beam-to-column connections was developed. The ductility capacity of the connections was found to scatter very significantly.
(b) A survey on damaged beam-to-column connections revealed that cracks that ev
entually caused fractures were initiated in one of the toe of the weld access hole, run-off tab, weld tip, or weld metal.
(c) Various types of weld access holes were examined, and their effects on the connection ductility capacity were quantified. It was found that modified details in which the size of the holes was reduced can ensure greater ductility capacity by a factor of 2 to 3 compared to the conventional details.
(d) Numerical analysis for frames subjected to large ground motions showed that the strain rate sustained by the beam end would be in a range of 0.2 to 0.3/s.
(e) Contrary to previous speculation, dynamic loading exhibited larger ductility capacity than quasi-static loading, with the mode of fracture being more ductile. Significant temperature rise during dynamic loading was found to be a likely cause for this mode of failure.
(f) Guidelines were provided as to the seismic design of welded beam-to-column connections in terms of the type of weld access holes, expected ductility capacity, and mode of failures. Less