• Journal of the Korea Concrete Institute
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• v.22 no.5
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• pp.719-725
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• 2010

The analysis and experimental program of reinforced concrete (RC) structures for resistance against such extreme loads as earthquake, blast, and impact have been carried by many researchers and designers. Under the extreme loads, a large amount of energy is suddenly exerted to the structure, hence if the structure fails to absorb the impact energy, catastrophic collapse may occur. To prevent catastrophic collapse of structures, reinforced concrete must have adeguate toughness or it needs to be strengthened. The FRP strengthening method and SFRC are studied widely in resistance of impact load because of their high energy absorption capacity. In this study, drop weight impact tests were implemented to evaluate the impact resistance of SFRC and FRP strengthened RC beam while the total steel fiber volume fractions was fixed at 0.75% carbon FRP flexural strengthened RC beams. Futhermore, to prevent the shear-plug cracks when the impact load strikes the beams, additional FRP shear strengthening method are applied. The experimental, results showed that the FRP strengthened RC SFRC beams has high resistance of shear-plug cracks and crack width and SFRC has high resistance of concrete spalling failure compared to normal RC beams. The FRP flexural and shear strengthening RC beams has weakness in the spalling failure because the impact load concentrated the concrete face which is not strengthened with FRP sheets.

• Tunnel and Underground Space
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• v.22 no.2
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• pp.77-85
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• 2012

In a material, micro-cracks can be progressively occurred, propagated and finally lead to failure when it is subjected to cyclic or periodic loading less than its ultimate strength. This phenomenon, fatigue, is usually considered in a metal, alloy and structures under repeated loading conditions. In underground structures, a static creep behavior rather than a dynamic fatigue behavior is mostly considered. However, when compressed air is stored in a rock cavern, an inner pressure is periodically changed due to repeated in- and-out process of compressed air. Therefore mechanical properties of surrounding rock mass and an inner lining system under cyclic loading/unloading conditions should be investigated. In this study, considering an underground lined rock cavern for compressed air energy storage (CAES), the mechanical properties of a lining system, that is, concrete lining and plug under periodic loading/unloading conditions were characterized through cyclic bending tests and shear tests. From these tests, the stability of the plug was evaluated and the S-N line of the concrete lining was obtained.