• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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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.

• Journal of the Korea Safety Management & Science
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• v.13 no.4
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• pp.101-108
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• 2011

In this paper deals with strength of glass fiber reinforced plastics produced by shouting machine was investigated by universal testing instrument. We can obtain following results by performing the strength evaluation of polymer composite material according as varied environment temperature. The effect of environmental temperature on Strength properties was more sensitive in the weld specimen than parent. When changed environmental temperature, variation of strength in the parent was much bigger than it of weld specimen, that is, matrix in the parent, orientation in the specimen ware more sensitive to environmental strength. Tensile strength of polycarbonate matrix was similar regardless of mold temperature.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.877-880
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• 2006

The stochastic nature of the tensile strength of concrete is investigated theoretically and experimentally. The tensile strength of concrete was modeled by a theory based on the failure probability of a crack arbitrarily oriented within a concrete body. According to this model, the stochastic nature of the tensile strength depend on the current stress state. This aspect was checked experimentally using a classical three point bend specimen and a rectangular plate specimen loaded at the center. It has been known that the biaxial strength is no different from the uniaxial strength. However, if the region where the tensile strength is constant gets small, the biaxial tensile strength increases and its stochastical variation decreases.

• Proceedings of the KWS Conference
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• 1999.05a
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• pp.72-73
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• 1999

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.3
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• pp.338-344
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• 2016

The study is actively being performed to increase fuel injection pressure of common rail system among countermeasures to meet the emission regulation strengthen of the Diesel engine. The common rail fuel injection tube in such ultra high pressure common rail system has the weakest structural characteristics against vibration that is generated by fuel injection pressure and pulsation during engine operation and driving. Thus the extreme durability is required for common rail fuel injection tube, and the drawing process is being magnified as the most important technical fact for strength of seamless pipe that is the raw material of common rail tube. In this respect, we analyzed the characteristic of dimension and stress variation of the ultra high pressure common rail fuel injection tube by variation of Die and Plug angle in drawing process. Based on the analysis, we tried to obtain the raw material strength of common rail fuel injection tube for applying to the ultra high pressure common rail system. As a result, Plug angle is more important than entry angle of Die and we could obtain the target dimension and strength of the ultra high pressure common rail fuel injection tube through optimization of Plug angle.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.66-72
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• 2005

Effect of the pH, molar ratio of Cu(II)/EDTA, concentration of Cu(II)-EDTA and ionic strength on the photocatalytic oxidation(PCO) of Cu(II)-EDTA in solar light was studied in this work. Experimental results in this work were compared with previous results obtained with UV-lamp. In the kinetics, Cu(II)-EDTA decomposition was favorable below neutral pH. The removal of Cu(II) and DOC was favorable as $TiO_2$ dosage increased. The initial rate for the decomplexation of Cu(II)-EDTA linearly increased as the concentration of Cu(II)-EDTA increased. The removal of Cu(II) and DOC was not much affected by variation of ionic strength with $NaClO_4$ as a background ion while much reduction was observed in the presence of background ions having higher formal charges. The removal trend of Cu(II) and DOC with variation of ionic strength and concentration of Cu(II)-EDTA in solar light was similar with that in UV light. Variation of the molar ratio of Cu(II)/EDTA showed a negligible effect on the removal of both Cu(II) and DOC. However, removal of both Cu(II) and DOC was two-times greater than that previous results obtained with UV light.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.651-654
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• 2003

Non-destructive testing is essential in the inspection of alteration, repair and new construction in construction industry. This paper is to evaluate the strength variation of fire damaged concrete by non-destructive testing. Furthermore, It is to infer the recovery degree of residual strength of fire-damaged concrete. For this purpose, researchers are exploring the performance of non-destructive testing method using ultrasonic testing and Schmidt hammer in concrete specimens. Testing is performed four-times: before fire test, directly after fire test, after 20 days and after 60 days.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.373-378
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• 1996

This paper presents the characteristics of various strengths of underwater non-segregation concrete. Three types of cements including low-heat cements has been used to make the test specimens for compressive strength, modulus of rupture and bond strength. The test specimens have been made both in ambient and underwater conditions to take into account the variation according to the environmental condition.

• Proceedings of the Korean Geotechical Society Conference
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• 1997.09a
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• pp.115-136
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• 1997

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.65-68
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• 2006

This study is aimed to investigate the strength variation of fire-damaged reinforced concrete column with polypropylene by non-destructive test. It is studied to infer the recovery degree of residual strength of fire-damaged concrete. For measuring the surface hardness of RC columns, Schmidt hammer test is used. Testing is performed four-times: before fire test, directly after fire test, after 30 days and after 4 months.