• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.148-152
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• 2000

The experimental study was performed to investigate the effects of centrifugal condition on the segregated layers of materials and the compressive strength of concrete for pretensioned spun high strength concrete (PHC) pile. The considering factors in the test were the centrifugal time and the magnitude of centrifugal force. These factors have been found to have found to have the great influence on the segregation and the concrete strength. The moderate centrifugal condition has to be fitted for the quality assurance in the production of PHC pile, especially to provide the adequate concrete cover over the tendons.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.2
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• pp.113-122
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• 2013

Recently there has been increased interest for the portal and shallow tunnel for an eco-friendly tunneling method. Semi cut & cover tunnel excavation techniques applied to concrete slab and construction and a growing number of cases, but there is no load combinations and arch concrete cross section for the applicable standards. Therefore, in this study, ground conditions and tunnel overburden thickness, thickness of backfill, overburden surface slope angle changes to a variety of conditions in order to propose standards for the semi cut & cover method was performed numerical analysis. Regression analysis method to the analysis of the results of numerical analysis, and linear regression equations derived to classify and organize a rational, economical, and safe semi cut & cover tunneling method based proposed.

• Journal of the Korea Institute of Building Construction
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• v.16 no.6
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• pp.513-518
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• 2016

This study evaluates the fire resistance performance for 60MPa high strength concrete reinforced by recycling polyethylene-terephthalate(PET) fiber(fiber content : 0.05 vol.%). Because there is no fire resistance test results for circular concrete column, a fire resistance test was carried out for circular concrete column specimens. As a result, it was confirmed that PET fiber was effective against the spalling control of high strength concrete. However, the specimen with cover thickness 30mm did not satisfy the temperature standard of main reinforcement, and the specimen with cover thickness 40mm satisfied the temperature standard of main reinforcement. Therefore, more than 40mm cover thickness was demanded for stable fire resistance performance.

• Journal of the Korea Institute of Building Construction
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• v.4 no.1
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• pp.119-126
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• 2004

Generally, reinforced concrete is one of the most commonly used structural materials and it prevents corrosion of steel bar by high pH of interior, But, as time elapsed, reinforced concrete structure become deteriorated by many of combined deterioration factors and environmental conditions. And, there are large number of deteriorate mechanism of the reinforced concrete structure and it acts complexly. It is recognized that steel bar corrosion is the main distress behind the present concern regarding concrete durability. In this study, to institute combined deterioration environments, established acceleration condition and cycle for combined deterioration environments has a resemblance to environments which are real structures placed. After that to confirm corrosion properties of reinforced concrete due to permeability with covering depth and types of surface cover under combined deterioration environments, measured carbonation velocity coefficients, chloride ion diffusion coefficients, water absorption coefficients, air permeability coefficients and electric potential, corrosion area ratio, weight reduction, corrosion velocity of steel bar. The results showed that an increase in age also decrease carbonation velocity coefficients, increase Chloride ion diffusion coefficients and increases water absorption coefficients. As well, an increase in age also increases corrosion of steel bar. Data on the development of corrosion velocity of steel bar with types of surface cover made with none, organic B, organic A, inorganic B, and inorganic A is shown. As well, permeability and corrosion velocity of steel bar with covering depth is superior to 10mm than 20mm. And it is confirmed permeability and corrosion properties of steel bar are closely related.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.179-186
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• 2008

Probing inside of concrete structures is one of the important steps in assessing condition of the structure. For the assessment, electromagnetic induction method and electromagnetic wave method are currently applied to the measurement of cover depth, and the detection of reinforcement embedded in concrete. To determine detection capability of locating reinforcement embedded in concrete, commercially available nondestructive testing (NDT) equipments have been tested. The equipments include electromagnetic wave system and electromagnetic induction system. In the tests, nine concrete specimens which have the dimensions of 1,000mm(length))${\times}$300mm(width) with thickness varying from 125mm to 150mm are used. The reinforcement are located at 45, 60, 100mm depth from the concrete surface. Horizontal reinforcement spacing has been set over 100mm. From the outcome, it is shown that error is increased as the diameter of reinforcement enlarge in case of using electromagnetic induction method. In case of using electromagnetic wave method, the detection of reinforcement embedded in deep is good in the view of reliability because of using the relative permittivity on the real cover depth.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.163-166
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• 2006

The purpose of the research is to assess the accuracy of steel bar detector among other nondestructive testing equipment. The result of previous research shows that the average errors of rebar detector are 14.7% for the cover depth, 2.3% for the rebar spacing, and 11% for the rebar diameter. But this experiment was performed at the laboratory and the mortar was used for covering the steel bars instead of concrete. In situ condition can be different from the laboratory's so the outcomes do not correspond with those of laboratory. This research was performed at the buildings to be reconstructed. Nondestructive and destructive testing can be performed side by side since the building if to be destroyed. Steel bar detector was operated on the beam and the column and concrete cover of those members was removed for the actual measurement of rebar depth, spacing, and diameter finally, presumed value can be directly compared with actual data.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.29-34
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• 2001

An experimental study was conducted to investigate the effectiveness of transverse reinforcement in reinforced concrete tied columns subjected to monotonically increasing axial compression. Eighteen large-scale columns(260$\times$260$\times$120mm) were fabricated to simulate similarly an actual structural members size. Effects of main variables such as the concrete compressive strength, the tie configuration, the transverse reinforcement ratio, the tie spacing, and the spatting of the concrete cover were studied in this research program.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.773-778
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• 2002

The variance characteristics of the calcium carbonate contents along to the concrete cover depth takes the prediction method of remaining service life of concrete. Calcium carbonate contents were measured by the Thermo Gravimetric/Differential Thermal Analysis method at three point, depth of 0.25cm, 0.75cm, 1.25cm from the surface of concrete. This prediction method contain some assumption that the chemical protection conferred on steel is through a passive protective oxide film which forms on steel in an environment at or above a pH of 10.5$^{4)}$ .

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.447-452
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• 1996

An experimental study was conducted to evaluate the bond performance of reinforcing bars embedded in high-strength concrete. Ten beam spice Specimens using concrete with compressive strength of 240kg/$\textrm{cm}^2$ and 640kg/$\textrm{cm}^2$ were tested. The effect of several variables on basic development length is discussed. The test results showed that the current trend in concrete specification of making the splice length longer to compensate for having smaller cover and spacing may not be an effective approach.

• Structural Engineering and Mechanics
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• v.59 no.5
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• pp.853-866
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• 2016

This paper examines a methodology for computing the probability of structural failure of reinforced concrete beams subjected to fire. The significant load variables considered are dead load, sustained live load and fire temperature. Resistance is expressed in terms of moment capacity with random variables taken as yield strength of steel, concrete class (or grade of concrete), beam width and depth. The flexural capacity is determined based on the design equations recommended in Indian standard IS456:2000. Simplified method named $500^{\circ}C$ isotherm method detailed in Eurocode 2 is incorporated for fire design. A transient thermal analysis is conducted using finite element software ANSYS$^{(R)}$ Release15. Reliability is evaluated from the initial state to 4h of fire exposure based on the first order reliability method (FORM). A procedure is coded in MATLAB for finding the reliability index. This procedure is validated with available literature. The effect of various parameters like effective cover, yield strength of steel, grade of concrete, distribution of reinforcement bars and aggregate type on reliability indices are studied. Parameters like effective cover of concrete, yield strength of steel has a significant effect on reliability of beams. Different failure modes like limit state of flexure and limit state of shear are checked.