• Fire Science and Engineering
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• v.25 no.6
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• pp.64-72
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• 2011

The concrete void slab structure with the existing mushroom slab, is the structure that maximizes the advantages, while minimizing the weakness with removing useless body force of the concrete part, located on the center of the slab cross-section, which does not need to support the structural weight. In this research, a fire test is performed to analyze how the blaze behave according to the thickness of slab cover, with the practical span length of concrete void slab for the slab length 7.5 m. With this heating test, we assumed the uniform-load-model considering fixed loads and live loads, and chose the standard fire test condition. We measured the temperature changes and the deflection character according to the depth from the heat exposure side, and assessed the resisting capability according to the standard KS F 2257-1. The result comes out with the EPS model can secure about 2 hour fire-resisting-capability with 50 mm of cover depth.

• Journal of the Korea Institute of Building Construction
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• v.23 no.2
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• pp.123-131
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• 2023

In this study, the analysis of concrete cracks was conducted with a total of three variables: coating thickness, oxygen diffusion rate, and reinforced diameter of reinforced concrete structures. Cracks occurred after about 3, 4, and 6 years at the coating thickness of 30, 40, and 50mm when the coating thickness was used as a variable, and cracks occurred after about 4, 5, and 10 years at oxygen diffusivity of 2e-9, 2e-11, and 2e-12(m²/s) when the oxygen diffusion rate was used as a variable. In the case of reinforcing bar diameters, cracks occurred after about 4, 3, and 2 years on the reinforcing bar diameters of D10, D19, and D25.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.79-86
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• 2006

This study was investigated to corrosion resistance of Cr-bearing rebars to macrocell corrosion caused by concrete with crack. Ten types of steel bars having different Cr contents were embedded in concretes with imitation crack. The corrosion resistance of the Cr-bearing rebar was examined by measuring half-cell potential, macrocell corrosion current, corrosion area and weight loss up to 105 cycles of salt spray testing. The results revealed that the Cr content required for corrosion resistance in a macrocell corrosion environment caused by chloride ion gap of $3kg/m^3$ was 9% or more. The corrosion-resisting performance of Cr-bearing rebar was particularly noticeable with a Cr content of 11% or more.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1037-1040
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• 2008

In order to predict the remaining life of marine concrete structures under climatic loads, it is necessary to develop an analytical approach to predict the time and space dependent deterioration of concrete structures due to mainly chloride attack up to corrosion initiation and additional deterioration like cracking of cover concrete. This study aims to introduce FEM model for life-time simulation of concrete structures subjected to chloride attack. In order to consider uncertainties in materials as well as environmental parameters for the prediction, Monte Carlo Simulation is integrated in that FEM modeling for reliability-based remaining service life prediction. The paper is organized as follows: firstly general scheme for reliability-based remaining service life of concrete structures is introduced, then the FEM models for chloride penetration, corrosion product expansion and cover cracking are briefly explained, finally an example is demonstrated and the effects of localization of chloride concentration and corrosion product expansion on service life using above model are discussed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.4
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• pp.28-36
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• 2021

It is known that buried rebars inside concrete structures are protected from corrosion due to passive layer. It is very important to delay the timing of corrosion or evaluate a detection of corrosion initiation for the purpose of cost-beneficiary service life of a structure. In this study, corrosion monitoring was performed on concrete specimens considering 3 levels of cover depth(60 mm, 45 mm, and 30 mm), W/C(water to cement) ratio(40.0%, 50.0%, and 60.0%) and chloride concentration(0.0%, 3.5%, and 7.0%). OCP(Open Circuit Potential) was measured using agar-based socket type sensors. The OCP measurement showed the consistent behavior where the potential was reduced in wet conditions and it was partially recovered in dry conditions. In the case of 30 mm of cover depth for most W/C ratio cases, the lowest OCP value was measured and rapid OCP recovery was evaluated in increasing cover depth from 30 mm to 45 mm, since cover depth was an effective protection against chloride ion ingress. As the chloride concentration increased, the effect on the cover depth tended to be more dominant than the that of W/C ratio. After additional monitoring and physical evaluation of chloride concentration after specimen dismantling, the proposed system can be improved with increasing reliability of the corrosion monitoring.

• Journal of the Korea Institute of Building Construction
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• v.10 no.5
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• pp.129-135
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• 2010

The purpose of this research is to secure fundamental data on the application of fibre as a fire resistance method for more than 60 MPa high-strength concrete through an examination of mechanical properties and fire resistance performance. The results are as follows: 1) When there are less than 0.5~1.0kg/$m^3$ contents of PP and NY fibre for 60MPa and less high strength concrete, 1.0kg/$m^3$ contents of PP and NY fibre for less than 80MPa high strength concrete and 1.5kg/$m^3$ contents of NY fibre for more than 80MPa high strength concrete, the effect of fibre contents on workability and strength development is not significant. 2) Based on the result of a 3-hour fire resistance test for mock-up column, it is necessary to secure 50 mm of covering depth for the regulation of fire resistance performance of high strength concrete to the standards of The Ministry of Land, Transport and Maritime Affairs. 3) It is necessary to secure more than 400mm of column size for stable fire resistance performance.

• Journal of the Korea Concrete Institute
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• v.22 no.2
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• pp.229-235
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• 2010

In this study, fire resistance performance of high strength concrete specimen with fireproof gypsum board was investigated for possible use in upgrading fire-resistant performance of the existing building and repair of fire damaged structures. Fire test of eight identical high strength concrete columns were carried out for 180 minutes in accordance with ISO-834. The temperature distributions in longitudinal reinforcement and concrete temperature at various depths were recorded. The fireproof performance of gypsum board and explosive spalling of concrete were observed. The specimens with 15 mm thick twoply fireproof gypsum board spalled after gypsum board crumbled regardless of fastening methods. However, when the thickness of fireproof gypsum board was more than 30 mm, it was possible to prevent the explosive spalling and control the rebar temperature. Although the effect of cover thickness could not be compared because the explosive spalling occurred, there seemed to be no difference in insulation efficiency.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2013.04a
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• pp.4-5
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• 2013

프리스트레스트된 프리캐스트 콘크리트 부재는 장경간이 가능하고 공장생산으로 품질관리가 용이하다. 그러나 프리스트레싱 텐던이 화재에 노출되는 경우 일반 철근에 비해 급격하게 강도를 상실해 구조물의 붕괴로 이어질 수 있다. 국내의 경우 실험에 기초한 내화성능에 대한 연구는 활발히 이루어지고 있으나 그에 반해 성능기반 설계법이 활성화 될 때 요구되는 수치해석적인 연구는 많이 부족한 실정이다. 따라서 본 연구에서는 문헌조사를 통해 이전에 수행된 실험 데이터를 통해 현재 외국에서 활발히 사용되는 수치해석 프로그램을 검증하고 수치해석 모델링을 통해 각각의 내화시간에 따른 적절한 피복 두께를 제안하였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.201-203
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• 2011

The purpose of this study was to develop and evaluate of fire resistive cladding systems for HSC(high-strength concrete) column, which was mainly constructed with aerogel blanket insulation material. The aerogel blanket-fire protective gypsum board cladding system showed that it clearly secure the fire resistance performance of HSC column when the reinforcing measures had achieved for four cross-sectional edge sides of structure and the system is well continued during the test period with no significant deformation or separation etc. It was checked out the 20mm thickness cladding system consist with AG(5mm)+FGB(15mm) can secure 3hour-fire resistance performance adequately.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2000.11a
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• pp.199-202
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• 2000

Compared with existing construction materials, ACM(Advanced Composites Material) possesses many advantage such as light-weight, high-strength, corrosion resistant properties, etc. In this study, utilizing those advantages of ACM, composite skin and comer plate for protection of concrete port structure are developed. Detailed procedure fur analysis, design and fabrication along with site installation for demonstration project are described. It is also demonstrated that pultrusion process for comer plate and VARTM process for composite skin are promising fabrication methods fer future civil infrastructure application.