• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.11a
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• pp.11-15
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• 2002

This study is intended to analyze the relationship between the rebound value of P type schmidt hammer and the compressive strength for a quality control of concrete. According to the results, the compressive strength of standard curing specimen increases in proportion to age, but that of air curing specimen hardly increases after 28 days. The rebound value of P type schmidt hammer, however, increases due to carbonation of concrete in air curing specimen. The correlativity between the rebound value and the compressive strength is very favorable in the case of standard curing specimen, but drops remarkably in the case of air curing specimen. Thus, as application of age coefficient is required for exact estimation of the compressive strength, the age coefficient is derived from this study. The age coefficient of P type schmidt hammer is higher at the age of 3 and 7days, and drops significantly, compared with the age of 28days. And it is lower before 28days than that of N type schmidt hammer suggested in Japan, and shows the similar tendency after 28days.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.236-239
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• 2004

The ternary blended cement(TBC) which the ability of resistance for seawater, the effect of decreation of hydration heat of concrete and long-age strength are known to be superior to other types was used to derive the estimation function of 91-age strength, 28-age strength with 28-age strength, 7-age strength respectively by analyzing the characteristics of statistics of compressive strength. The sample specimens was made after testing the variations of slump, air-contents during 30 minutes for consideration of transportation period. The functions might be expected to be useful for construction smoothness and reasonable quality control of concrete with TBC.

• Architectural research
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• v.18 no.4
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• pp.179-184
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• 2016

The structure must be periodically checked and measures must be taken to prevent deterioration in building construction. From this point of view, a nondestructive test is essential to estimate whether the construction of buildings is proper, and whether the dimension of depositing concrete is consistent and without damage. This study estimated the thickness of the concrete component of construction framework using the ultrasonic velocity method and the impact echo method, in order to investigate reliability of the estimation of the thickness of normal strength concrete and high strength concrete, leading to the following conclusions. In the estimation of the thickness of the concrete structures, specimens of normal strength of 24MPa and specimens of high strength of 40MPa demonstrated an average error rate of 5.1% and 2.2%, respectively. The impact-echo method, one of the non-destructive tests, is verified as an efficient diagnostic technique. With this information, we will determine specific standards for the maintenance of structures, and the re-creation of lost building blueprints.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.67-72
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• 2016

Aluminum alloy is one of light weight material and it is used to make LNG tank and ship. However, in order to weld aluminum alloy high density heat source is needed. In this paper, I-butt welding of Al 5083 with 6mm thickness using Plasma-MIG welding was carried out. The experiment was performed to investigate the influence of plasma-MIG welding parameters such as plasma current, wire feeding rate, MIG-welding voltage and welding speed on the tensile strength of weld. In addition we suggested 3 strength estimation models which are second order polynomial regression model, multiple nonlinear regression model and neural network model. The estimation performance of 3 models was evaluated in terms of average error rate (AER) and their values were 0.125, 0.238, and 0.021 respectively. Neural network model which has training concept and reflects non -linearity was best estimation performance.

• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.409-419
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• 2013

A T-stub connection with high-strength bolts under tensile force is affected by prying action force and the contact force, among others, between members. If a design equation that does not consider such prying action force and contact force between members is not proposed, the T-stub under tensile force is liable to be fractured under the strength lower than the estimated design strength. To prevent it, many studies have proposed contact force estimation equations between members as well as the prying action force of the T-stub connection with high-strength bolts. However, no design equations based on such research have been proposed in South Korea. Therefore, this study aims to propose an estimation model for more accurate prying action force and contact force, and improve on previously proposed estimation models by implementing the three-dimensional, nonlinear finite element analysis. Throughout the results of three-dimensional, nonlinear finite element analysis, the prediction model proposed in this research for the prying action force and contact force of a T-stub provided much more accurate estimation than that of a existing prediction model previously suggested.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.04a
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• pp.26-29
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• 1993

To analyze the using of recycled aggregate on concrete as the substitude aggregate is important problem for the reuse of waste matter and prevention of environmental pollution. Therefore, this study is designed for investigating and analyzing the mechanical properties and early estimational properties of strength on concrete using aggregate of the waste concrete. And is aimed to provide the fundamental data for recycled aggregate.

• Communications for Statistical Applications and Methods
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• v.3 no.3
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• pp.187-194
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• 1996

We treat the problem of estimating reliability R = P[Y < X] in the stress-strength model in which a unit of strength X is subfected to enviromental stress Y./ In this paper several nonparametric approaches to estimation of R are analyzed and compared by simulations.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.280-285
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• 1995

In order to predict the behavior of column confined with spirals, the accurate estimation of confining stress by spiral is very important, Thus a number of models have been proposed for calculating the confining stress by spiral. However, in these equations, it was not considered the effects of the difference of mechanical characteristics related to the application of high strength concrete and spiral in structures. In this study, a model equation for calculation of the confining stress by spiral was proposed based on the test results investigated here. The proposed equation included the effects of concrete strength, spacing and yield strength of spirals

• Magazine of the Korean Society of Agricultural Engineers
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• v.41 no.6
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• pp.82-89
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• 1999

This paper present the strength estimation of precast concrete products by chloride ion penetration method. The relation between the strength of precast concrete product and the ion passing charge is linear and a numerical model of FCK =515.96-0.201Q is prposed. The results showe good agreement at about 9.0% error ration with the estimated model results for real precast concrete product.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.3
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• pp.53-60
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• 1997

Generally, a safety estimation based on the buckling strength is carried out to evaluate the strength of plate members in the design process of ship hull structures and more accurate and efficient tool for the buckling strength estimation of enormous plate members of ship structure is naturally demended for saving design process. While, in the reason that the design codes of classification societies do not consider the various effects or include some effects roughly, considerate safe side results are suggested occasionally. In this study, advanced buckling strength estimation system prepared various classification buckling evaluation codes and new evaluation code considering the effects of in-plane tension, plate boundary condition, lateral load & residual stress is developed using the window management system of engineering workstation. Additionally maximum deflection estimation formula is equipped for the increase of fabrication reliability of thin plate ship structure. From this evaluation system, more reliable buckling safety of plate panel will be guaranteed in the ship hull design stage. In order to expand the use of this system pc version system will be developed sooner or later.