• Explosives and Blasting
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• v.22 no.4
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• pp.1-6
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• 2004

In this study, dimension and scale factor of explosives were calculated. Proper dimension and scale factor were considered. Scale factor of 1/256 was obtained when scaled factor of the length was l/4. This value is similar to the ratio of explosives of model test and demolition structure. It seemed that scale factor of length should be larger than 1/4.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.208-215
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• 2003

지진하중에 대한 구조물의 동적 거동과 성능을 예측 평가하기 위하여 실험적 방법들이 흔히 사용되고 있으나, 실험장비의 제약과 구조물의 규모 등으로 대부분 축소모형실험에 의존하고 있다. 그러나 일반적인 상사법칙(similitude law)은 탄성범위에서 유도된 것으로 지진거동과 같은 비탄성 거동을 예측하는 경우에는 한계가 있다. 또한 탄성범위 내에서도 크기효과(size offset)가 발생하므로 축소모형의 실험결과를 원형 구조물에 직접 적용하는 것은 많은주의가 필요하다. 본 연구에서는 원형 구조물(prototype)과 축소모형(scaled model)을 모두 실험 대상으로 하여 실제 축소모형만을 실험하여 원형 구조물의 거동을 예측하는 경우의 문제점을 확인하고 그 해결방법을 모색하고자 한다. 실제로 축소모형실험에서는 원형 구조물의 경계조건을 정확히 재현하기 어려우며, 실험모형의 제작과정과 실험과정에서의 모든오차가강성의 변화로 반영되어 나타난다. 따라서 본 연구에서는 기하학적 상사율과 변화된 강성비(stiffness ratio)를 함께 고려하여 고유진동수의 오차를 보정하고 비탄성 거동중에도 직접적인 실험결과의 비교가 가능한 상사법칙을 제안하였다. 더불어 제안된 상사법칙을 적용한 유사동적실험 (pseudodynamic test)을 수행하여 실험오차보정(experimental error compensation)효과를 검증하였다.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.6
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• pp.49-57
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• 2003

Although there are several experimental techniques to evaluate the seismic behavior and performance of civil structures, small-scale models in mast of physical tests, instead of prototypes or large-scale models, would be used due to a limitation on capacities of testing equipments. However, the inelastic seismic response prediction of small-scale models has some discrepancies inherently because the similitude law is generally derived in the elastic range. Thus, a special attention is required to regard the seismic behavior of small-scale models as one of prototypes. In this paper, differences between prototypes and small-scale models pseudodynamically tested on steel column specimens are investigated and an alternative to minimize them is suggested. In general, small-scale models could have the distorted stiffness induced from some experimental errors on test setup, steel fabrication and so on. Therefore, a modified similitude law considering both a scale factor for length and a stiffness ratio of small-scale model to prototype is proposed. Using the modified similitude law to compensate experimental errors, the pseudodynamic test results from modified small-scale model are much improved as compared with the results of prototype. According to the pseudodynamic test results of small-scale steel models, it can be concluded that the modified similitude law proposed could be effective in simulating the seismic response of prototype structures.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.510-514
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• 2008

우수 관거 시스템에서 맨홀의 설치 시 연결관 내부와 맨홀의 내부는 여러 가지 수리학적 조건이 다르므로 수두손실의 발생이 필연적일 수밖에 없다. 현재 계획 또는 설계단계에서 수행되고 있는 관거 시설의 수리계산에는 연결관 내에서의 마찰손실만을 고려하여 설계를 수행하고 있으며, 맨홀에서의 수두 손실은 거의 대부분 고려되지 않고 있다. 단지 맨홀에서의 수두손실을 저감하기 위하여 하수도시설기준(환경부, 2005)상의 단차 및 인버트 규정만 있을 뿐, 우수 관거 설계에 직접적으로 필요한 적절한 맨홀의 손실계수가 제시되지 않고 있는 실정이다. 국외에서는 축소 수리 모형을 이용한 실험과 수치해석 기법 등을 이용하여 맨홀에서의 손실계수를 산정하는 연구가 꾸준히 진행되어 왔으나 국내에서는 맨홀의 손실계수 산정에 관한 연구가 미흡한 실정이며, 더욱이 맨홀에서의 손실계수 산정을 위한 상사성 적용에 관한 연구는 전무한 실정이다. 그러므로 본 연구에서는 맨홀의 축척 변화에 따른 손실계수의 변화를 분석하기 위하여 하수도시설기준(환경부, 2005)의 특 1호(사각형) 맨홀을 각각 1/2과 1/5로 축소 제작하고, 수리실험 장치를 제작하였다. Froude 상사 법칙을 적용하여 1/2의 축소 모형의 실험 조건을 1/5 축소 모형의 값으로 환산하였으며, 각 축소 모형에 대한 수리 실험을 실시하였다. 과부하된 맨홀의 손실계수를 예측하는데 Froude 상사법칙의 사용 가능성을 확인 하였으며, 1/2 축소 모형과 1/5 축소 모형에서 산정된 손실계수 값이 0.45로 일치하고 있으므로 우수 관거 시스템의 맨홀 설계 시, 축소 수리 모형실험에서 산정된 손실계수의 직접적인 적용이 가능하다고 판단된다.

• Tunnel and Underground Space
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• v.17 no.4
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• pp.295-300
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• 2007

A method using detonating cord was suggested to control the blasting source for scaled model test. Blasting of 5 concrete block was carried out to verify the method. It was proved that blasting power can be controlled by suggested method. It seemed to be reasonable to use the reduction ratio based on the explosion heat.

• Explosives and Blasting
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• v.25 no.1
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• pp.53-65
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• 2007

When doing a blasting demolition on RC structures made of scale models, scale model members considering both a proper scale factor and mechanical characteristics of materials have to be similar to prototype RC members to analyze the collapse behavior of RC structures. In this study. a similitude law considering the density of prototype materials is calculated. Both mix of concrete and arrangement of reinforcement have been described referring to Concrete Standard Specification as well as Design Standard of Concrete Structure. The scale factor on scaled concrete models considering maximum size of coarse aggregate is about one-fifth of a cross section of prototype concrete members. A scale factor on staled steel bar models is about one-fifth of a nominal diameter of prototype steel bar. According to the mechanical test results of scale models, it can be concluded that the modified similitude law may be similar to compressive strength of prototype concrete and yield strength of prototype steel bar.

• Explosives and Blasting
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• v.22 no.1
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• pp.33-43
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• 2004

In this study, a comparison was made between the resulting behaviors of scaled model test and particle flow analysis for blasting demolition of a reinforced concrete structure. For the test and analysis, a progressive failure of a five-story structure was considered. The dimension analysis was carried out to properly scale down the real structure into the laboratory size. The test model was made of the mixture of gypsum, sand and water along with soldering lead to analogy reinforcing steel bars. The ratio of mixing components was chosen to best represent the scaled down strength and deformation modulus. The columns and girders of the structure were precasted in the laboratory and assembled right before the blasting test. The numerical analysis of the blasting demolition was carried out using PFC2D (Particle Flow Analysis 2-Dimension by Itasca). The results of the blasting of concrete lahmen structure showed roughly identical demolition behavior between scaled model test and numerical test. For the blasting of the reinforced concrete structure, the results were more identical and closer to the real demolition behavior, since the demolition behavior was better represented in this case due to the increased tensile strength of the component.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.3
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• pp.213-221
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• 2009

This paper presents the concrete placement method of tunnel lining to improve the concrete lining quality such as cavities, cracks of the concrete lining. In order to perform this study, the occurred cracks initially in the concrete lining are reviewed and analyzed. From the review, the improvement methods to minimize the defects of concrete lining are suggested. To confirm the efficiency of new concrete placement approaches and the scale of tunnel section, two types of the scaled model tests are carried out and analyzed in model scales of 1/20 and 1/7. The 1/20 scaled model tests are carried out using the existing experimental rigs. The 1/7 scaled model tests are carried out in new test rigs developed in this study. The concrete placement rates obtained from the experimental results are analyzed and compared with themselves. In the existing concrete placement method, 1/20 scale model test than 1/7 scale model test have increased concrete placement rates but It is clearly found that two kinds of experimental studies show the similar results in improvement methods and good agreement with new concrete placing approach.

• Tunnel and Underground Space
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• v.26 no.6
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• pp.508-515
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• 2016

In this study, we compared the stability of the pillars by using room and pillar mining method with the four models with different stiffness and pillar overlap ratio. The experimental models consist of two plaster models (overlap ratio 0%, 100%) and two cement models(overlap ratio 0%, 100%). The soft and hard rocks are modeled by plaster and cement models respectively. In these experiments, the model materials with strength values reflecting the calculated scaled factors not been used, so it is not a true scaled model test that reproduces in situ state in the laboratory. Experimental results show that the different overlap ratio pillars are one of the factors that can affect the stability of the mine.

• Fire Science and Engineering
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• v.28 no.2
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• pp.14-19
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• 2014

A current standard exist only on the surface tension in the current domestic wetting agent technology standards, so it is difficult to the performance evaluation of the wetting agent through the standard. So this study presents the optimized performance evaluation methods by scale model experimental equipment in order to present techniques for performance evaluation of wetting agents. The purpose of this study is to investigate validity of experimental results of the self-designed scale model experiment equipment by a comparative analysis of experimental results of the NFPA 18 experiment and the experiment using the self-designed scale model experiment equipment. As a result of a comparative analysis of experimental results of the NFPA 18 experiment that evaluate only the permeation performance on the contton and the experiment using the self-designed scale model experiment equipment that evaluate the permeation performance and fire extinguishing performance on wood flour, the discrimination of the permeation performance was confirmed in both the NFPA 18 experiment and the self-designed scale model experiment equipment. And a result of self-designed experiment equipment have clear discriminatory more than NFPA 18 by internal temperature measurement using the thermocouples.