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Effect of Rotational Restraint on Inelastic Buckling of Steel Column at Elevated Temperatures
구자훈,이철호,신동진 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2
When a fire develops within the fire compartment of a building, the columns in the compartment are heated, whereas the beams and columns outside the compartment remain cold. Hence, the relative stiffness ratio between the cold members and heated column increases. Consequently, the end-rotational restraint on the heated column is increased, and the effective buckling length of the heated column becomes shorter compared with the ambient temperature condition. However, studies regarding the effect of increased end rotational restraint on heated columns are rare. Although some recommendations to consider this effect are available in representative design standards, they are suggested under limited or ideal conditions and hence not applicable under general conditions. In this study, a procedure for calculating the effective length factor of non-sway steel columns with general end restraints at elevated temperatures is proposed based on the classical Euler column theory and tangent modulus concept. The proposed procedure is validated based on a test-backed nonlinear finite element analysis. It is shown that the proposed equations can be combined with the existing column buckling curve to predict the column buckling strength with significantly increased accuracy compared with the methods suggested by representative design standards.
Energy-based Beta Peak Extraction from Dynamic Resistance Curves
구자훈,박영도,구남국 대한용접접합학회 2022 대한용접·접합학회지 Vol.40 No.5
Recently, the importance of welding monitoring is emerging, and in particular, many studies using characteristic values of dynamic resistance curves are being conducted. Among the characteristic values, β-peak, peak on the dynamic resistance curve, contains important information on the extent to which the nugget grows. A common way to extract the β-peak is to determine the local maximum point followed by the local minimum point in the dynamic resistance curve. However, for dynamic resistance curves where local extremum values are unclear, extracting the β-peak in this manner is difficult. Therefore, in this study, a method using heating energy for β-peak extraction was proposed. Heating energy is the energy used until the β-peak is reached. Typically heating energy does not significantly differ even if the welding conditions differ for the same material. Based on the results, the β-peak of the dynamic resistance curve without the clear peak was extracted, and 11 characteristic values were calculated. Among them, three values that had a high correlation with the nugget diameter were selected. Using these values, the nugget diameter was predicted through linear regression analysis.
구자훈,한민섭 고전문학한문학연구학회 2012 고전과 해석 Vol.13 No.-
平百濟塔, 혹은 平濟塔은 당나라 蘇定方이 백제를 멸망시킨 기념으로 쓴 것으로, 현재 國寶 9호인 부여 定林寺址 五層石塔 1층 塔身에 새긴 글이다. 평백제탑에 대한 기록은 『新增東國輿地勝覽』에 蘇定方碑라는 명칭으로 처음 보이고, 조선시대에 여러 문인들에게 계속 관심을 받았다. 또한 18세기 조선과 청나라 문인들의 교유가 활발해지면서 청나라 문인들에게도 알려져, 이 비문의 탁본을 소장한 청나라 문인들도 많아졌다. 특히 청 고증학자 翁方綱의 아들 翁樹崐은 秋史 金正喜와의 교유를 통해 평백제탑 탁본을 받았고, 이에 대해 釋文을 남겼다. 고려대학교 도서관 華山文庫에 소장되어 있는 옹수곤의 「平百濟塔 釋文」은 그가 평백제탑에 대한 연구를 진행하여 김정희에게 문의한 글이다. 이는 柳得恭, 成海應, 韓致奫, 金正喜 등이 남긴 평백제탑 釋文 등과 함께 조선후기에 활발히 이루어진 金石文 연구의 수준을 보여주는 자료이며, 조선후기 한중 문인 교유의 일면을 보여주는 자료이다. The writing called as Pingbaijita(平百濟塔), or Pingjita(平濟塔) is the one engraved on Pagoda body on the first flood of Buyeo Jeongrimsaji Ocheungseoktap(扶餘 定林寺址 五層石塔), now designated as the national treasure No. 9, in memory for the fact that Tang Dynasty brought Baekjae Dynasty(百濟) into the ground. The record on Pingbaijita first appeared on 『Xinzengdongguoyudishenglan(新增東國輿地勝覽)』 as Sudingfangbei(蘇定方碑), continuously attracting attention of lots of writers during Chosun Dynasty period(朝鮮). Also, the exchange between Chosun and Qing Dynasty literati become active, the record became known even to Qing Dynasty literati, so that various Qing Dynasty literati got to possess the rubbing of this epitaph. Especially, Weng Shukun(翁樹崐), so of Weng Fanggang(翁方綱), got to know Pingbaijita through companionship with Chusa Kim Jeonghee(秋史 金正喜) and left Shiwen(釋文) with respect to that. Weng Shukun's 「Pingbaijita Shiwen」 housed in Hwasan Library(華山文庫), a Korea University(高麗大學校) Library, is the writing about which he asked Kim Jeonghee making research of Pingbaijita. This is materials that show the level of Jinshiwen(金石文) study as actively made in the later part of Chosun Dynasty period together with Pingbaijita Shiwen left by Yu Deukgong(柳得恭), Sung Haeeung(成海應), Han Chiyun(韓致奫), Kim Jeonghee(金正喜), et al. The materials also demonstrate an aspect of companionship between Korea and China in the later part of Chosun.