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CFS로 휨 보강된 RC부재의 보강겹수에 따른 구조성능 변화
서수연(Seo Soo-Yeon),김경태(Kim Kyong-Tae),윤승조(Yoon Seung-Joe),윤현도(Yun Hyun-Do),최기봉(Choi Gi-Bong) 대한건축학회 2008 大韓建築學會論文集 : 構造系 Vol.24 No.2
Strengthening method using carbon fiber sheets have been developed for the rehabilitation of structures and applied to the concrete member. However, it is still questionable whether their structural capacity has been well kept without any deterioration as time goes. According to a few inspection results about RC buildings with retrofitted members by CFS, there have been found loss of strengthening using CFS because of the detachment of CFS from the concrete face, which causes the bond failure of CFS. The appearance of this loss may be initiated at just after retrofit construction. And it will be more serious when the layer number of CFS increases. In order to minimize above mistake in retrofit design using CFS, more exact evaluation process to predict the bond loss of CFS is required. The final objective of this research is to propose the guideline and method for estimating resistance capacity of strengthened structure as time goes by. In this paper, as a first step, previous equations to predict flexural strength of member retrofitted by CFS are analyzed and evaluated through a test work. And a nonlinear sectional analysis is performed using a commercial analysis program. In experimental work, specimens with the amounts of carbon fiber and strengthening method as test parameter are tested and their behavior is discussed. From the test, the flexural capacity was not linearly increased even if the layer number of CFS increased when it was more than two. The overall nonlinear behavior of RC member retrofitted with CFS could be suitably predicted by the analytical process in this paper by considering the bond loss.
화재손상된 철근콘크리트 깊은 보의 전단경간비에 따른 구조성능 변화
서수연(Seo Soo-Yeon),윤승조(Yoon Seung-Jo),김영만(Kim Yeong-Man),최기봉(Choi Ki-Bong) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.11
This paper presents experimental result of reinforced concrete deep beams with various shear span-to-depth ratios damaged by fire. Main parameters in the test were fire exposure duration and shear span-to-depth ratio. Nine RC deep beam specimens were made and six of those were exposed to fire by following standard fire loading curve. And then beam test was performed for those under simple support condition. Strength variation of materials by the exposure time and temperature of fire was evaluated through material test for concrete and reinforcements damaged by fire. In order to predict the specimen's structural capacity, analysis was performed using nonlinear sectional analysis and truss analogy. From the research, it was found that the strength of RC deep beam damaged by fire was more seriously affected by level of temperature than exposure time during fire loading. However, concrete tended to be dry as the exposure time increased so that the overall behavior of member changed to brittle failure mode. In order to suitably predict the strength of deep beam damaged by fire, the change of properties of concrete and reinforcements at each location should be well defined and appropriately reflected in analysis model.