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손상과 크리프의 상호작용에 의한 조적조 기둥의 복합거동
김정중 ( Jung Joong Kim ) 한국복합신소재구조학회 2014 복합신소재학회논문집 Vol.5 No.2
Since the collapse of historical masonry structures in Europe in the late 1990’s, the interests in understanding the long-term effect of masonry under sustained compressive stresses have increased. That requires combining the significance of time-dependent effects of creep with the effect of damage due to overstress to realize the evolution of cracks and then failure in masonry. Meanwhile, composite analysis of masonry columns was proven effective for realizing ultimate strength capacity of masonry column. In this study, a simplified mechanical model with step-by-step in time analysis was proposed to incorporate the interaction of damage and creep to estimate the maximum stress occurred in masonry. It was examined that the interaction of creep and damage in masonry can accelerate the failure of masonry.
김정중(Kim Jung-Joong),손장열(Sohn Jang-Yeul) 한국생활환경학회 2009 한국생활환경학회지 Vol.16 No.2
Recently sports stadiums have been built not only for athletic sports but also for various events such as live concerts and recitals. The number of the stadiums which are covered by a half dome have been increasing. Therefore it is very important to solve the sound obstacle problem caused by the half dome. But sound designs of most of stadiums, with only a few as an exception, have not been planned properly and the proper sound absorption materials have not been used. This study investigates four World Cup stadiums (Seoul, Incheon, Daegu, Busan). First, sound factors according to the location in the stadium were compared by the design standard through field measurement. Then architectural sound absorption structure was analyzed and in turn the sound factors were considered totally for obtaining the proper reverberation time, RASTI, and sound pressure level. The average reverberation time for dome stadiums Busan were 6.03 seconds, longer than arch(Daegu) stadiums which were 3.8 seconds. However, the variance of the reverberation time at low frequencies(125 ㎐ and 250 ㎐) between the lower tiers(tier 1, 2) and the higher tiers(tier 4, 5) was larger in arch stadiums Daegu by about 2 seconds. The RASTI values for shield kite stadiums Seoul and dome stadiums Busan were between 0.38 and 0.50 indicating that audibility was ‘Poor’ to ‘Fair’. But otherwise, cone stadiums incheon achieved a RASTI value of 0.50 for all spectator seats and arch stadiums Daegu satisfy audibility standards for all areas except the playing field.
실리케이트 연결구조를 고려하여 포졸란 물질을 포함한 시멘트 바인더의 반응도를 결정하는 방법
김정중(Kim Jung Joong) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.6
본 논문에서는 ²⁹Si MAS (Magic Angle Spinning) NMR (Nuclear Magnetic Resonance) 실험을 통하여 시멘트 구성물질의 반응도를 결정하는 방법을 소개한다. 시멘트 구성물질의 반응도를 중량비에 따른 가중치로 평균하여 시멘트의 수화도를 결정한다. 구성물질의 반응도는 아브라미(Avrami) 방정식을 따르는 것으로 가정한다. 또한, 포졸란 물질을 사용한 시멘트에 대해서는 ²⁹Si MAS NMR 결과를 활용하여 포졸란의 변환율을 결정하는 방법도 소개한다. 사례연구와 함께 제안된 방법에 대한 계산과정을 실었다. In this study, a methodology to determine the degree of reactivity for compositions of cements was introduced. The degree of hydration can be determined by the weighted average of the degree of reactivity for major compositions of cements. It is assumed that the degree of reactivity for major compositions of cements follows Avrami equation. Moreover, the conversion fraction of pozzolan materials for pozzolan blended cement pastes can be extracted from the results of ²⁹Si nuclear magnetic resonance (NMR) experiments. The calculation procedures for the proposed methodology are presented with case studies.