• Journal of Korean Society of Forest Science
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• v.102 no.1
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• pp.90-96
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• 2013

This study was conducted to investigate a stability trend within 6 above average and 4 blow average erosion control dams, which were selected by The Korean Association of Soil and Water Conservation and were built in 1990s in Gyeonggi and Gangwon Province. The study was aimed to measure rebound hardness of upstream face, flood way and downstream face from those dams selected by using 'Concrete Test Hammer'. The main purposes of the study are selection of compression strength prediction equation and scope of wavelength, which successfully demonstrate non-destructive test results for erosion control dams. There is an opportunity to increase disaster prevention ability when stability vulnerability of concrete erosion control dam is detected in a timely manner. Results of the compression strength investigation express that there is a consistency with visual inspection of stability that has been processed by The Korean Association of Soil and Water Conservation. We concluded that a prediction equation, which was developed by Architectural Institute of Japan (AIJ), shows highest suitability in Korean erosion control dams when stability investigation is performed. The detailed criteria for the test result are 'stable', 'detail inspection required' and 'poor' for over 300 $kgf/cm^2$, 250~300 $kgf/cm^2$ and below 250 $kgf/cm^2$ respectively. Standards for stability of Korean erosion control dam and a compression strength prediction equation (that corresponds to the standards of the stability) should be established on the basis of chronological data of erosion control dam compression strength. Systematical approach for stability inspection that carries out remodeling or repair when problem on erosion control structures are detected through visual inspection and simple stability test, is necessary for the future disaster prevention.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.259-264
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• 1994

The 1986 AASHTO Guide for the Design of Pavement Structures introduced the resilient modulus as a definitive material property to characterize roadbed soil. Although the incorporation of resilient modulus represents a significant acvance in pavement design practice, the test procedure for resilient modulus is complicated and time-consuming. Therefore, it is necessary to develop data base of resilient modulus for the soils frequently encountered; and to develop the reliable correlations between resilient properties and parameters from simple routine tests, In this study, resilient modulus tests were performed on five cohesive soils sampled from in-service subgrades. The stress at 1 percent axial strain in unconfined compression test(su1.0%) was found as a good indicator of the resilient modulus, and unique relationship between Mg and Su1.0% was obtained. A simple chart to estimate the resilient modulus at different levels of confining stress and deviator stress was also developed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.199-203
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• 2003

Idler of excavator are large product with diameter 500 - 600 mm and parts of a power transmit device. The object of the paper is developed large products by hot closed-die forging. The forging process which is proposed from numerical analysis and various tests is developed a large products with good quality. To estimate the design process parameters such as working load, temperature and flash thickness so on, numerical analysis are used by DEFORM 2D. To obtain a flow stress data and optimal forging temperature is carried out hot compression and tensile test at a various temperature range. Developed product is tested mechanical properties of elongation, hardness and tensile strength so on. Test results are presented excellent mechanical properties.

• Structural Engineering and Mechanics
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• v.46 no.1
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• pp.111-135
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• 2013

An experimental study has been carried out on square plain concrete (PC) and reinforced concrete (RC) columns strengthened with carbon fiber-reinforced polymer (CFRP) sheets. A total of 78 specimens were loaded to failure in axial compression and investigated in both axial and transverse directions. Slenderness of the columns, number of wrap layers and concrete strength were the test parameters. Compressive stress, axial and hoop strains were recorded to evaluate the stress-strain relationship, ultimate strength and ductility of the specimens. Results clearly demonstrate that composite wrapping can enhance the structural performance of square columns in terms of both maximum strength and ductility. On the basis of the effective lateral confining pressure of composite jacket and the effective FRP strain coefficient, new peak stress equations were proposed to predict the axial strength and corresponding strain of FRP-confined square concrete columns. This model incorporates the effect of the effective circumferential FRP failure strain and the effect of the effective lateral confining pressure. The results show that the predictions of the model agree well with the test data.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.669-673
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• 2001

The objective of this paper is to predict and evaluate the sealing performance of the thermoplastic rubber component in the proto-design stage. The large strain and large deformation properties of rubber are modeled by strain energy function and the related material constants are calculated from the test data. The viscoelastic property of the rubber is also considered using the coefficients in a Prony series representation of a viscoelastic modulus ken the compression stress relaxation test. The results show that the current design of cap mount system has 2-different stiffness caused by the cap-mount contact and the viscoelastic property of rubber plays an important role in time dependent deformation.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2002.05a
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• pp.159-162
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• 2002

In this paper the stress-strain curves of bearing steels at hot working conditions are obtained by compression test with a computer controlled servo-hydraulic Gleeble 3800 testing machine and elongations and reductions of area of the bearing steels are obtained by tensile test with a computer controlled servo-hydraulic Gleeble 1500 testing machine. These tests have been focused to obtain the flow stress data and optimal hot forging conditions under various conditions of strain rates and temperatures. The strain rate sensitivity exponent and reduction of area of the materials are evaluated. Experimental results are resented for various conditions of temperatures and strain rates.

• 기술발표회
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• s.2006
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• pp.66-72
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• 2006

The ground anchoring has been utilized over 40 years. It is growing the application of the removal ground anchor with tension force for holding earth retaining constructions in the city. It transmits tension stress of prestressed steel wire through grouting to fixed the ground that is of great advantage adjacent ground stability. Nowadays, we can find the compression dispersion anchor on many site. But, it has some problems in behavior of anchors because of impossible to tense p.c strand uniformly under the existing equipment due to different length of p c strand. Hence, motive of this research was to study the application of the newly developed tension system, that analyze and compare with the current anchoring method build on the data of in-site test and laboratory test. As a result, in case of auto back tension system, it became clear that tension pressure was equally distributed among the steal wires but the existing tension system showed sign of instability by indicating stress deflection of about 30% compare with design load. This can cause an ultimate failure of the concentrated p.c strand and a shear failure of ground.

• Steel and Composite Structures
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• v.35 no.4
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• pp.495-508
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• 2020

Double skin composite walls are alternatives to concrete walls to resist gravity load in structures. The composite action between steel faceplates and concrete core largely depends on the internal mechanical connectors. This paper investigates the structural behavior of novel composite wall system with T section and under combined compressive force and bending moment. The truss connectors are used to bond the steel faceplates to concrete core. Four short specimens were designed and tested under eccentric compression. The influences of the thickness of steel faceplates, the truss spacing, and the thickness of web wall were discussed based on the test results. The N-M interaction curves by AISC 360, Eurocode 4, and CECS 159 were compared with the test data. It was found that AISC 360 provided the most reasonable predictions.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.473-479
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• 1996

Until now, we assumed in the time-dependent analysis of concrete structure that tensile creep has same characteristics as compressive creep has. But, in according to results of researches, it appears that tensile creep is different from compressive creep in quantity and in mechanics because tensile creep is affected significantly by micro cracking. The test results indicate that the creep behavior of concrete in compression and tension is rather different. The test data shows that the amount of creep under tensile loading is larger than that under compressive loading. In this paper, a realistic tensile creep model is suggested and incorporated in the formulation. In order to get more accurate results of time-dependent analysis. The present study indicates that the long-term deflection of concrete structures under realistic tensile creep model is somewhat larger than that under ordinary compressive creep model.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.142-143
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• 2006

Combinatorial methods are being used increasingly to develop the next generation of polymers, coatings and adhesive formulations. Allied to this approach, a new genre of measurement and characterization methods are emerging. These characterization techniques are required to handle and take measurements from small samples. This has led to a number of uses for this technology which usefully fall between convention test specimen and micro- or nano-scale test methods. A versatile measurement platform will be presented which can offer useful indentation, puncture, compression, adhesion and scratch resistance data for a wide variety of material types and that continues to develop and evolve in capability.