• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.125-132
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• 2010

In the recent construction industry, an external strengthening method using fiber reinforced polymers has been widely used. Since reinforced concrete structures strengthened with fiber reinforced polymers are always under sustained loads, influence of creep and shrinkage on the structures is inevitable. Due to the creep and shrinkage, behaviors of the structures, such as deflection, deformation, recovery capability, strength and so on are also under the influence of creep and shrinkage. Thus, in order to estimate efficacy, creep recovery and residual strength of FRP strengthened RC beams, long-term flexural experiments and static flexural experiments were carried out. As the result of the experiments, FRP strengthened RC beams were very effective in terms of deflection control. Furthermore, the strengthened beams had higher immediate deformation recovery than immediate deformation. Through the static flexural experiments, it was shown that the CFRP strengthened beam had high residual strength. It seems that the sustained loads did not affect bond and residual strength of the beams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.171-178
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• 2008

The object of this study is to propose a rate of vibration increase in the analysis of temporary rail non-fixed in the vertical direction and characterize the nonlinear dynamic behavior of temporary rail while considering longitudinal and latitudinal load, vibration and lifting. The rate of vibration increase is proposed through measurement of an actual structure that is largely affected by loading and vibration of the superstructure. Dynamic behavior was additionally characterized by the dynamic response resulting from nonlinear dynamic finite element analysis with vehicle loading, including the rate of vibration increase. As a result, the rate of vibration increase by the vibration of an Auto Bar Machine is determined as 7% and the maximum stress in the analysis of the nonlinear rail is increased 14.5% over that of linear rail, and temporary rail is shown to be very sensitive to the velocity of the superstructure.

• Corrosion Science and Technology
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• v.14 no.3
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• pp.147-152
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• 2015

Corrosion of steel reinforcement is a major factor in the deterioration of harbour and bridge structure. Steel corrosion in concrete must be checked for assessing the condition of a reinforced concrete structure. There are several ways how to measure the corrosion condition of reinforced concrete, but the corrosion potential measurement is a very simple, rapid, cost-effective and non-destructive technique to evaluate the severity of corrosion in reinforced concrete structure, therefore commonly used by engineers. However some particular situations may not relate to the reinforcement corrosion probability and a simple comparison of the corrosion potential data with the ASTM C876 Standard on steel reinforcement corrosion probability could be meaningless and not give reliable informations because of environment factors as oxygen concentration, chloride content, concrete resistance. Therefore this paper explains the risk of corrosion assessment in reinforced concrete structure and how many factors can affect the reliability of the corrosion potential data.

• Magazine of the Korea Concrete Institute
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• v.14 no.2
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• pp.17-23
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• 2002

화재로 인한 건물의 화해 정도는 건축구조불의 안전성에 크게 영향을 미치게 된다. 특히, 철근 콘크리트 구조물이 화재로 인하여 고열을 받게되면, 그 구조적인 내력이 저하되므로, 이에 대한 안전성 검토는 매우 중요하다. 콘크리트의 고온성상은 시멘트의 종류, 골재의 석질. 배합, 함수율, 재령에 따라 달라진다. 또한, 화해를 입은 콘크리트조 건물은 수열조건에 따라 매우 복잡한 양상을 띄게된다. 일반적으로 화재 건물의 콘크리트 부재에서 나타나는 화해는 각 부재의 폭열 또는 콘크리트의 박리에 의한 주근의 노출 등 직접적인 손상과 보의 변형 기둥의 좌굴, 열팽창에 의한 전단균열 등의 2차 적인 피해가 있다. 그 화해 정도는 지진피해의 파괴현상과 유사한 경우도 있다. 이와 같이 콘크리트 부재의 화재 정도를 검토하기 위해서는 콘크리트의 고온성상 파악이 중요하다.(중략)

• Magazine of the Korea Concrete Institute
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• v.14 no.5
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• pp.40-46
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• 2002

산업화 도시화에 따른 건축물의 밀집과 고층화의 환경에서 화재 재해 발생은 인명피해 및 재산피해에 치명적인 결과를 가져올 수 있으며 화재로 인한 인명 및 재산 피해는 두말할 것도 없이 막대한 국가적 손실을 초래한다고 할 수 있다. 따라서 화재발생을 사전에 억제하는 구조물의 방화ㆍ내화구조 및 피난계획, 소화설비 소화활동설비 등에 대한 방재 연구와 더불어 화재발생후 화재의 원인조사와 구조물의 재사용 여부 또는 보강 필요성, 자산의 평가의 과학적인 근거를 위해 신뢰성 있는 안전성 평가에 대한 연구가 필요한 실정이다.(중략)

• Magazine of the Korea Concrete Institute
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• v.14 no.2
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• pp.77-82
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• 2002

일반적으로 공동주택 지하주차장과 같이 구조물이 대형화되거나 복잡할 경우 구조물의 응력취약 부위에서 균열, 누수 등의 문제가 발생할 확률이 크다. 이에 대한 대책으로 설계자들은 신축줄눈을 선호하고 있으나 신축줄눈은 시공상의 어려움과 사용 중 잦은 하자 발생이라는 문제점을 안고 있다. 이 때문에 근래에 들어 대형 건물을 한 단위로 처리하고 철근으로 보강하려는 경향이 있으나 구속도 차이에 따라 균열, 누수 등의 문제가 여전히 발생하고 있다. 이를 해결하기 위하여 수축대를 설치하여 일정 요구량의 초기 수축량을 수축대에서 흡수하고 이후 수축대 부위에 콘크리트를 메워 일체화시킴으로써 초기 수축에 의한 균열을 상당부분 방지할 수 있다.(중략)

• Journal of the Korea Concrete Institute
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• v.14 no.2
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• pp.199-206
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• 2002

The objective of this study is to investigate the seismic behavior and evaluate structural performance of columns in Ordinary Moment Resting Concrete Frames (OMRCF). For this purpose 3 story OMRCF building was designed and detailed in compliance to ACI 318 (1999). Only gravity load is considered for the design. It is important to note that details strongly relate to the structural performance. The 1st story columns in the 3 story building are considered in this study since 다lese columns shall resist the largest axial and lateral forces during an earthquate. Four test specimens were made for representing the upper part and lower part of exterior and interior columns. All specimens are two-third scale. Based on the test results this study estimates deformation, ductility, strength, and energy absorption capacities as well as plastic hinge length.

• Magazine of the Korea Concrete Institute
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• v.14 no.6
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• pp.88-95
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• 2002

최근 국내에 60층을 초과하는 초고층 구조물들이 많이 건설되고 있으며, 콘크리트 품질의 향상 특히 콘크리트의 고강도화에 힘입어 이를 이용한 철근 콘크리트 고층 구조물들이 증가하고 있다. 이에 따라 이들 초고층, 초대형 구조물을 지지할 수 있는 고축력, 고연성의 기둥에 대한 설계 및 시공이 요구되고 있으며, 이에 가장 적합한 구조요소라 할 수 있는 콘크리트 충전 강관기둥(Concrete Filled Steel Tube Columns : CFT Columns)의 설계 및 시공에 관심이 높아지고 있다. 이러한 콘크리트 충전 강관기둥은 콘크리트가 강관에 의해 둘러싸여지기 때문에 축하중 저항 능력이 증가되는 장점과 동일한 단면으로 H형강을 사용한 순수 철골조 H형강 기둥의 강축(strong axis)과 약축(weak axis) 문제해결과 동시에 강성 (stiffness)을 증가시킬 수 있으며, 내화 성능이 향상되고 거푸집 대체 재료로 사용되는 등 여러 가지 장점을 지니고 있다. 한편 충전 강관기둥에 작용하는 축하중은 대부분 콘크리트가 부담하게 되는데 이러한 충전강관 기둥의 장점을 극대화하기 위해서는 보통강도 콘크리트보다는 압축강도 및 탄성계수가 큰 고강도 콘크리트의 사용은 불가피하게 된다.(중략)

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.341-344
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• 2008

In this paper, the effect of flame cutting order of tendons on the concrete stress was investigated experimentally. For this, the three slab specimens with 14 tendons were cast and tested. During the detensioning, the longitudinal and transversal strain were measured. Test results showed that the measured strains of transversal stirrups were varied by the cutting order.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.555-562
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• 2016

The objective of the present study is to evaluate the shear transfer capacity of transverse reinforcement at the concrete interfaces with smooth construction joint. The transverse reinforcing bars were classified into two groups: V-type for the arrangement perpendicular to the interface and X-type for inclined-crossing arrangement. The transverse reinforcement ratio at the interface varied from 0.0045 to 0.0135 for V-type and 0.0064 to 0.0045 for X-type. The mechanism analysis proposed for monolithic concrete interface, derived based on the upper-bound theorem of concrete plasticity, was modified to evaluate the shear friction capacity of concrete interfaces with smooth construction joint. Test results showed that the specimens with X-type reinforcement had lower amount of relative slippage at the interface and higher shear friction capacity than the companion specimens with V-type reinforcement. This observation was independent of the unit weight of concrete. The mean and standard deviation of the ratios between the experimental shear friction strength of smooth construction joints and predictions obtained from the proposed model are 1.07 and 0.14, respectively.