• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.909-914
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• 1998

제어봉구동장치는 원자력발전소에서 사용되는 기기로서, 가늘고 긴 수직 외팔보의 형상을 하고 있어 지진과 같은 동적하중에 취약한 구조를 갖고 있다. 따라서 발전소가 건설되는 지반의 다양한 지진하중에 대한 동적해석이 중요한 설계요건으로 되어 있다. 본 논문에서는 제어봉구동장치의 고유진동수를 제어하기 위한 기초연구로써 제어봉구동장치의 설계변경이 동적특성에 미치는 영향, 즉 고유진동수에 대한 설계 민감도 해석을 수행하였다. 해석 방법으로는 유한요소 프로그램의 구조 해석 결과에 변분법을 이용한 설계 민감도법을 사용하였다. 해석 결과는 유한차분에의한 결과와 일치함을 보였고, 제어봉구동장치의 초기설계 단계에서 유용한 정보로 활용할 수 있음을 확인하였다. 또한 이러한 결과는 최적설계 프로그램등과 연계되어 구조물의 설계 개선에 많은 도움을 줄 것으로 판단된다.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.183-191
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• 2008

This study evaluated influence of the loading head dimension on characteristics of deformation strength ($S_D$) of asphalt mixtures. Kim test and Wheel tracking (WT) test were conducted to evaluate $S_D$ characteristics with relation to WT results for various mixtures. The $S_D$ values and coefficient of variation of $S_D$ values of r=10mm were smaller than those of r=10.5mm. It was also found that $S_D$ values obtained using r=10mm loading head showed high correlations with rut parameters of WT test. It was indicated that the aggregate size and radius (r) of round cut were statistically significant variables on $S_D$ at = 0.05 level in the analysis of variance. However, in interaction of r and aggregate size showed no significance within $10{\sim}19mm$ aggregate size at the same level. Therefore, it was concluded that the diameter (D) of 40mm and the bottom edge radius (r) of 10mm was suitable dimension of loading head for deformation strength test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1991.11a
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• pp.110-115
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• 1991

일반적으로 거의 모든 재료의 기계적인 물성치들이 여러가지 하중조건에 의해 변화하는데 그 중 탄성계수는 하중속도, 온도, 재료의 특성에 따라 변화한다. 지금까지 국내에서의 연구동향을 보면 하중속도가 탄성계수에 미치는 영향에 대한 연구보고는 미약한 실정이다.(중략)

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.259-270
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• 2007

This paper presents an analytical method of evaluating the flexural behavior of RC (reinforced concrete) beams strengthened with high-strengh bars. The former experimental results were used to compare with the analytical results. The experimental results also outline the advantages of externally strengtheng method with high-strenght bars. To evaluate the flexural behavior of RC beams strenghtend with unbonded high-strength bars, this paper proposes a method involving a simple strength-summation method. This method basically assumes that the total strength of RC beams strengthened with high-strength bars is equal to the sum of the strengths of the RC beams and the high-strength bars. This analytical method also includes the effects of compressive force due to the tension from high-strength bars. A comparison of the analytical and experimental results leads to the conclusion that the simple strength-summation mothod can simulate the flexural behavior of RC beams strengthened with high-strength bars with a good level of accuracy.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.15-22
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• 2003

In the conventional load transfer analysis for a steel pipe drilled shaft, it was assumed that the concrete's strain is the same as the measured steel's strain and the elastic modulus of the steel and the concrete calculated by the formular as prescribed by specification is used in the calculation of pile axial load. But, the pile axial load calculation by conventional method differed to some extent from the actual pile load. So, the behavior of a steel pipe drilled shaft could not be analyzed exactly. Thus, the necessity to measure the strain for each pile component was proposed. In this study, a new approach for load transfer measurement of large diameter drilled shafts was suggested ; the strain of each pile component(i. e., steel and concrete) was measured by DRS(Deformable Rod Sensor), the elastic modulus was determined by the uniaxial compression test for concrete specimens made at test site and a value of elastic modulus was evaluated as average tangential modulus corresponding to the stress level of the (0.2-0.6)$f_{ck}$. Field application was confirmed by the results of load transfer measurement tests for 3 drilled shafts. The errors for calculated pile head load were -11 ∼16% and 3.4% separately.

• Explosives and Blasting
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• v.37 no.1
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• pp.14-23
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• 2019

It has been an always issue for the blasting or the impact analysis to consider the strength characteristics of the rock materials associate with loading rate dependency. Due to the nature of transient loading, the dynamic rock test requires a careful technique to achieve the stress equilibrium state of the specimen. In this study, to investigate the relationship between the rock dynamic strength and the stress equilibrium state, a series of dynamic uniaxial compression tests for Pocheon granite were performed. As a result, the unbalanced stress state on the specimen can lead to the premature failure on the specimen and the less estimation of dynamic strength characteristic as well as the overestimation of strain rate. Consequently, a careful consideration of rock fracture process to achieve the dynamic force balance on the specimen should be required to make an reasonable evaluation of rock dynamic strength.

• Explosives and Blasting
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• v.38 no.1
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• pp.23-29
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• 2020

The measurement technique with dynamic shock sensor was widely used in academic experiment for blasting and impact. However, most of dynamic sensors are expensive so that it needs to be protected by external housing structures or damping devices. In this study, the calibration method for dynamic shock sensor under the distortion by external structures. Hopkinson pressure bar system was adopted to measure the input acceleration to the sensor, and it was compared to the acceleration measured by accelerometer with customized damping device. Consequently, it is conclued that this method can be useful to calibrate the dynamic shock sensor under the linear distortion.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.05a
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• pp.259-259
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• 2003

• Proceedings of the Korean Nuclear Society Conference
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• 1998.10a
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• pp.221-221
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• 1998

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.297-302
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• 1998

유한요소법을 이용하여 스프링으로 연속 지지되고 축방향 하중이 작용하는 핵연료봉의 자유진동 해석올 수행하였다. 본 해석에는 지지격자 지지점에서 핵연료봉의 변위가 구속되지 않는 실제 경계조건을 반영하였다. 이러한 경계조건은 지지점 스프링 상수에 의하여 핵연료봉 해석모델의 탄성항이 약화되는 현상을 반영할 수 있어서 지지점이 구속된 기존의 모델보다 고유진동수를 작게 예측한다. 스프링 상수가 어떤 임계값 이하를 갖는 경우 고유진동수 뿐만 아니라 모드형상도 크게 변하기 때문에 지지점을 구속한 모델에 의한 해석은 실제 진동현상을 상당히 왜곡 할 수 있다. 핵연료봉에 작용하는 축방향력이 인장력에서 압축력으로 감소함에 따라 고유진동수도 감소하지만 핵연료봉의 고유형상은 변하지 않았다. 지지격자 스프링 상수의 점진적인 감소와 핵연료봉 축방향 압축력의 감소를 동시에 적용하는 경우 고유 진동수는 두 변수를 별도로 적용했을 때 얻은 최소값의 변화에 따르는 경향을 나타내었다.