• 한국지진공학회논문집
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• 제23권2호
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• pp.119-129
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• 2019

Many reinforced concrete (RC) buildings constructed prior to 1980's lack important features guaranteeing ductile response under earthquake excitation. Structural components in such buildings, especially columns, do not satisfy the reinforcement details demanded by current seismic design codes. Columns with deficient reinforcement details may suffer significant damage when subjected to cyclic lateral loads. They can also experience rapid lateral strength degradation induced by shear failure. The objective of this study is to accurately simulate the load-deformation response of RC columns experiencing shear failure. In order to do so, model parameters are calibrated to the load-deformation response of 40 RC column specimens failed in shear. Multivariate stepwise regression analyses are conducted to develop the relationship between the model parameters and physical parameters of RC column specimens. It is shown that the proposed predictive equations successfully estimated the model parameters of RC column specimens with great accuracy. The proposed equations also showed better accuracy than the existing ones.

• 한국안전학회지
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• 제4권1호
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• pp.25-39
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• 1989

Cyclic temperature creep tests were carried out an AS 7075 alloy specimens were subjected to a constant load and stepwise temperature cycles in which temperature was fluctuated between 30$0^{\circ}C$ and 25$0^{\circ}C$ with three different cycle ratios. The highest frequency of cycling was 1 cycle per 10 hr and the lowest one was 1 cycle per 12 hr. From the creep experimental results with the above conditions the creep strain under cyclic temperature can be predicted easily by introd ucing the equivalent steady temperature because defined by Eq.(16), but the rupture life is 1.1 time than those of constant temperature because of effect of temperature history at tertiary creep range. Besides thlis result, the results of the creep test under cyclic temperature conditions are respectively compayiea with calculated rupture lives using the life fraction law and Eq.(18). The agreement between the obseried rupture times and calculated ones is fairly good. So creep rupture lives can be respectively predicted using life fraction law and Eq.(18).

• 비파괴검사학회지
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• 제29권4호
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• pp.360-367
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• 2009

공용중인 콘크리트 구조물의 건전성 평가를 위해서는 하중 증가에 따른 내부의 변형특성 및 손상을 예측하고 비 파괴적으로 상시 모니터링 할 필요가 있다. 본 연구에서는 철근 콘크리트 슬래브 시편을 대상으로 단계별 하중 재하(loading, holding, unloading)에 따른 음향방출 실험을 실시하였으며 휨 시험하의 인장균열, 전단균열 및 철근 콘크리트의 부착 상태, 반복하중에 의한 AE 신호의 특징과 신호 발생 양상을 분석하였다. 또한 음향방출법(a.oustic emission)에 있어 손상 정도를 유추할 수 있는 대표적 인자인 Felicity ratio를 분석하여 콘크리트 구조물의 상시감시 및 안전진단에 음향방출 기술을 적용하기 위한 분석기법을 제시하고자 한다.