• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 봄 학술발표회 논문집
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• pp.221-226
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• 1994

A safety evaluation of cable tunnel, which is a concrete box structure with telecommunication facilities in it, exposed to fire is given. The immediate field observation was performed to find out any sign of sudden structural failure. In some region, where the fire intensity was heavy, the spalling of concrete cover in upper slab occurred. Next, more careful investigation was done with proper non-desturctive testing methods and structural analysis taking into account the changes in material properties due to fire. It seems that there is no severe damage on concrete, reinforcements and over all structural system.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
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• pp.435-440
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• 1994

It is considered to pressing problem that the develpment of the rapid and simple method and measuring instrument, can evaluate for quality of concrete at early period. Accordingly in this paper proposed to earlier evaluation method on quality of concrete using resistance method and ultra-sonic pulse velocity test. It was found to the possibility of development on test method and instrument through a series of fundmental investigation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.383-391
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• 1997

The prediction of effective properties of heterogeneous material like concrete is of primary importance in design or analysis. This paper os about micromechanice-based evaluation of elastic moduli of concretes considering composite material behavior. In this study, micromechanixe-based schemes for the effective elastic modui of the lightweight foamed concrete and the normal concrete are proposed based on averaging techniques using a single-layered inclusion model and a multi-phase and multi-layered inclusion model. respectively, For the verification's sake, elastic moduli evaluated in this study are compared with experimental data and results by existing formula.

• Computers and Concrete
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• 제14권4호
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• pp.387-403
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• 2014

The aim of this study is to assess the structural performance of deteriorated reinforced concrete bridge piers, and to provide method for developing improved evaluation method. For a deteriorated bridge piers, once the cover spalls off and bond between the reinforcement and concrete has been lost, compressed reinforcements are likely to buckle. By using a sophisticated nonlinear finite element analysis program, the accuracy and objectivity of the assessment process can be enhanced. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), is used to analyze reinforced concrete structures. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. Advanced deteriorated material models are developed to predict behaviors of deteriorated reinforced concrete. The proposed numerical method for the structural performance assessment of deteriorated reinforced concrete bridge piers is verified by comparing it with reliable experimental results. Additionally, the studies and discussions presented in this investigation provide an insight into the key behavioral aspects of deteriorated reinforced concrete bridge piers.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.195-196
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• 2018

The Research is underway to utilize heavyweight concrete for various applications. One of them is to use heavy concrete as a marine concrete such as a breakwater to resist wave. Marine concrete is often complex in shape and requires high fluidity. When the heavyweight concrete is high fluidity, there is a high risk of segregation due to the high density of the coarse aggregate. Therefore, we evaluate the fluidity of heavyweight concrete using heavy fine aggregate. As a result of the fluidity evaluation of the heavyweight concrete, the fluidity of the heavy fine aggregate was similar to that of ordinary concrete. Therefore, it is considered that the use of heavy fine aggregate in the development of high fluidity heavyweight concrete will be one of the methods.

• 한국실내디자인학회논문집
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• 제25권5호
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• pp.121-129
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• 2016

With the ingenious properties of unconstrained formativeness and frank expression of materiality the exposed concrete became popular with numerous architectures. The application of the exposed concrete has expanded to indoor environments such as commercial and residential spaces beyond the building exteriors with the uncompromising nature of its materiality. The purpose of this study is to conduct sensibility evaluation of the exposed concrete finish in interior spaces. The sensibility evaluation is conducted through a survey on a set of space models of the exposed concrete finish. The three rendered space models were evaluated by emotional vocabulary of 18 pairs of words. The result were as follows: First, the emotions derived from the exposed concrete finish are 'modern', 'cold', 'simple', 'restrained', 'rough', 'dark', 'new', 'chic', 'familiar' and 'eco-friendly'. Second, three sets of space models with alternative materials on walls and floors in exposed concrete interior space showed clear difference in sensibility. A space with the exposed concrete finish on the floor, the walls and the ceiling showed the results of 'cold', 'dark', 'rational' and 'masculine'. In the exposed concrete finish environment with wood flooring 'comfortable', 'warm', 'bright' senses and with white paint finish on the wall 'bright', 'practical', 'ordinary' and 'restrained' senses were obtained. Third, all three images achieved senses of 'chic', 'modern', 'new', 'pleasant', 'environment friendly' and 'satisfactory'. The modernity and stylish expressions of the exposed concrete finish were kept with the application of different material finishes as well as complementing its cold and rough expressions with warmth and brightness.

• Computers and Concrete
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• 제19권1호
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• pp.111-120
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• 2017

This study aimed to design the accelerated life testing (ALT) of concrete, which stimulating the special natural environment maximumly. Its evaluation indexes, such as dynamic elastic modulus, mass and ultrasonic velocity were measured, and the variation of relative mass and relative dynamic elastic modulus of concrete were studied. Meanwhile, the microanalysis method was used. Moreover, an exploratory application of the stochastic approach, the Weibull distribution and the lognormal distribution, were made to assess the durability of concrete structures. The results show that the ALT for simulating natural environment is more close to the service process of concrete structure under actual conditions; The relative dynamic elastic modulus can be used as the dominant durability evaluation parameters, because it is more sensitive to the environmental factors compared with the relative quality evaluation parameters; In the course of the concrete deterioration, the destruction of the salt freezing cycle is the dominant factor, supplemented by other factors; Both of those two stochastic approaches can be used to evaluate the reliability of concrete specimens under the condition of ALT; By comparison, The lognormal distribution method is better to describe the reliability process.

• 방사성폐기물학회지
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• 제19권1호
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• pp.133-140
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• 2021

This study evaluates the radioactivity of concrete waste that occurs due to large amounts of decommissioned nuclear wastes and then determines the surface dose rate when the waste is packaged in a disposal container. The radiation assessment was conducted under the presumption that impurities included in the bio-shielded concrete contain the highest amount of radioactivity among all the concrete wastes. Neutron flux was applied using the simplified model approach in a sample containing the most Co and Eu impurities, and a maximum of 9.8×104 Bq·g-1 60Co and 2.63×105 Bq·g-1 152Eu was determined. Subsequently, the surface dose rate of the container was measured assuming that the bio-shield concrete waste would be packaged in a newly developed disposal container. Results showed that most of the concrete wastes with a depth of 20 cm or higher from the concrete surface was found to have less than 1.8 mSv·hr-1 in the surface dose of the new-type disposal container. Hence, when bio-shielded concrete wastes, having the highest radioactivity, is disposed in the new disposal container, it satisfies the limit of the surface dose rate (i.e., 2 mSv·hr-1) as per global standards.

• 비파괴검사학회지
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• 제29권3호
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• pp.230-234
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• 2009

As concrete ages, the surrounding environment is expected to have growing influences on the concrete. As all the impacts of the environment cannot be considered in the strength-estimating model of a nondestructive concrete test, the increase in concrete age leads to growing uncertainty in the strength-estimating model. Therefore, the variation of the model error increases. It is necessary to include those impacts in the probability model of concrete strength attained from the nondestructive tests so as to build a more accurate reliability model for structural performance evaluation. This paper reviews and categorizes the existing strength-estimating statistical models of nondestructive concrete test, and suggests a new form of the strength-estimating statistical models to properly reflect the model uncertainty due to aging of the concrete. This new form of the statistical models will lay foundation for more accurate structural performance evaluation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.136-141
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• 1995

The early evaluation on strength of concrete is useful to achieve on quality control and improvement of properties of concrete. Especially, we could say that the confidence of construction is increased by the increase durability and safety building, due to early evaluation. In this study, was proposed to ultra-sonic pulse method as a early evaluation method for strength of concrete with main parameter, sush as W/C ratio and S/A ratio. The experiment results are summarized to follow as : $\circled1$ The ultra-sonic pulse was decreased as the increase of W/C ratio. $\circled2$ The maximum value for the ultra-sonic pulse velocity and compressive strength was presented in the case of 40% S/A ratio and these value was decreased as the change of S/A ratio over 40% $\circled1$ The relationship of the ultra-sonic pulse velocity and compressive strength on 28days according to the change of W/C and S/A ratio is to be: $F_{28} = -209193R^2 + 384417R - 1763441$(W/C Ratio) $F_{28} = 1726R^2 - 774R - 502 (S/A Ratio)