• Magazine of the Korea Concrete Institute
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• v.8 no.4
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• pp.191-199
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• 1996

Cracks occur in mass concrete structures during construction if temperature of the concrete due to heat of hydration is suddenly changed. The temperature is also changed after placement of mass concrete by construction environments on structures. However, methods which can analyze the temperature history of mass concrete considering the construction environments have not been developed yet. In this research, an algorithm and finite element analysis program is developed for the analysis of temperature rise history of mass concrete considering quantitatively heat transfer coefficient and construction environmental conditions such as climate conditions, curing conditions, forms and form removal, and additive curing. By comparing analysis results of the program with experimental data, other research data, and analysis results by a finite element program ADINAT, validity and accuracy of the program is verified.

• Advances in concrete construction
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• v.13 no.5
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• pp.395-410
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• 2022

This study collected the results of material tests and full-scale pumping tests using 127 types of concrete mixtures with compressive strength ranging from 24 to 200 MPa. The results of 242 material tests showed high correlations between the viscosity of the lubricating layer and concrete, between the slump and the yield stress of concrete, between the water-binder ratio and the viscosity of lubricating layer, and between the time required to reach 500 mm of slump flow and concrete viscosity. Based on these correlations, pumpability was predicted using 101 pumping test conditions, and their accuracy was compared to the actual test results. When the rheological properties of concrete and the lubricating layer were directly measured, the prediction result showed the highest accuracy. A high accuracy can be achieved when the measured viscosity of the lubricating layer, a key determinant of concrete pumpability, is reflected in the prediction of pumpability. When measuring rheological properties is difficult, the slump test can be used to quantitatively predict the pumpability despite the lower accuracy than those of other prediction methods.

• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.157-166
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• 2005

This article involves architecting prototype-fuzzy expert system for designing the nominal cover thickness by means of fuzzy inference for quantitatively representing the environment affecting factor to reinforced concrete in chloride-induced corrosion environment. In this work, nominal cover thickness to reinforcement in concrete was determined by the sum of minimum cover thickness and tolerance to that defined from skill level, constructability and the significance of member. Several variables defining the quality of concrete and environment affecting factor (EAF) including relative humidity, temperature, cyclic wet and dry, and the distance from coast were treated as fuzzy variables. To qualify EAF the environment conditions of cycle degree of wet-dry, relative humidity, distance from coast and temperature were used as input variables. To determine the nominal cover thickness a qualified EAF, concrete grade, and water-cement ratio were used. The membership functions of each fuzzy variable were generated from the engineering knowledge and intuition based on some references as well as some international codes of practice.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.10
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• pp.11-18
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• 2018

In this study, the cross-sectional image has been acquired to evaluate the aggregate distribution affecting quality of lightweight aggregate concrete, and through the binarization method, the study is to calculate the aggregate area of upper and lower sections to develop the method to assess the aggregate distribution of concrete. The acquisition of cross-section image of concrete for the above was available from the cross-sectional photography of cleavage tension of a normal test specimen, and an easily accessible and convenient image analysis software was used for image analysis. As a result, through such image analyses, the proportion of aggregate distribution of upper and lower sections of the test specien could be calculated, and the proportion of aggregate area U/L value of the upper and lower regions of concrete cross-section was calculated, revealing that it could be used as the comprehensive index of aggregate distribution. Moreover, through such method, relatively easy image acquisition methods and analytic methods have been proposed, and this indicated that the development of modeling to assess aggregate distribution quantitatively is available. Based on these methods, it is expected that the extraction of fundamental data to reconsider the connectivity with processes in concrete will be available through quality assessment of quantitative concrete.

• Journal of the Korea Institute of Building Construction
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• v.3 no.1
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• pp.139-146
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• 2003

The special requirements of high-performance concrete(HPC) could be enhanced property over others such as compressive strength, durability, and construction practices. In order to satisfy these requirements a series of laboratory trial mixes and following mock-up test of reinforced concrete wall at field were performed in this study. The objective of this study was to quantitatively evaluate the workability, compressive strength, and the increased heat of hydration caused by the increase of the specific weight of cement according to various variables. Six example series designed about a minimum compressive strength of 500kgf/$\textrm{cm}^2$ at 28 days, and an approximately slump and slump flow of 25cm and 60cm respectively were tested. The selection process of the specific weight of water and the percentage of fly-ash transposition determined to be most suitable for the production of HPC is presented in the following paper.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1616-1623
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• 2011

The concrete track was applied for Gyungbu 2nd phase high_speed railroad line as a basic track structure. Two track structures, ballasted track and non_ballasted concrete track, have a different train load transfer mechanisms. However, it's rare to see about research results related with it. So, to understand dynamic response characteristics of the concrete track and roadbed, we measured accelerations of carbody and bogie, vertical and lateral load, stress and displacement of rail, and earth pressures of subgrade at ${\bigcirc}{\bigcirc}{\bigcirc}$k930 station of Gyungbu high_speed line during speed up tests before opening it. Based on these measured results, we could evaluate the level of dynamic responses of the track quantitatively.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.533-538
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• 2001

This study was peformed to control the thermal crack of the mat footing slab in the multi-purposed buildings. In this study, we executed the mixing design of concrete to satisfy the workability and the quality according to the site conditions. And, we evaluated quantitatively about the possibility of thermal crack by using hydration heat analysis system. Finally, we proposed the optimal mixing conditions, curing methods and curing period which all factors are considered. As a results, the optimal mixing conditions were : W/B 41%, unit binder 375kg/$cm^{2}$, FA replacement ratio 20%. Lowest thermal stress was 22.0kgf/$cm^{2}$ and at that time thermal crack index was over 1.5, when the coefficient of thermal conductivity was lowest among the curing conditions. And, the total curing time was estimated at 6.7 days according to curing steps.

• International Journal of Concrete Structures and Materials
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• v.10 no.sup3
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• pp.109-121
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• 2016

Recently, as the use of high-performance materials and complex composite methods has increased, the need for advanced design specifications for steel-concrete composite structures has grown. In this study, various design provisions for ultimate flexural strengths of composite beams were reviewed. Design provisions reviewed included the load and resistance factor design method of AISC 360-10 and the partial factor methods of KSSC-KCI, Eurocode 4 and JSCE 2009. The design moment strengths of composite beams were calculated according to each design specification and the variation of the calculated strengths with design variables was investigated. Furthermore, the relationships between the deformation capacity and resistance factor for flexure were examined quantitatively. Results showed that the design strength and resistance factor for flexure of composite beams were substantially affected by the design formats and variables.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.85-86
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• 2009

A nondestructive test method based on the self-compensating frequency response function is proposed in this paper to quantitatively measure the attenuation in concrete materials. Since the proposed technique measures inherent attenuation of material itself, more stable experimental results can be expected. In advance, comparison of the experimental results to those obtained by other methods shows the repeatability and accuracy of the proposed technique.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.204-209
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• 2003

The purpose of this study is to develop new seismic design concept based on ductility demand for reinforced concrete bridge columns in areas of low to moderate seismicity. In developing the ductility based design approach, relationship between ductility demand and transverse reinforcement demand should be quantitatively developed. To evaluate ductility capacity of reinforced concrete columns, analytical models and a non-linear analysis program, NARCC have been developed. Based on analytical and experimental results, an equation for relationship between curvature ductility and displacement ductility, an equation for designing the transverse confinement reinforcement for ductility demand, and a new seismic design concept of RC bridge columns are presented.