• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.2
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• pp.108-115
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• 2016

In this paper, fluid-structure of interaction behavior of a fluid-filled cylindrical polymer container impacted by a high speed spherical projectile was studied using ALE(Arbitrary Lagrangian Eulerian) method. The hydrodynamic ram phenomenon occurred by the impact projectile penetrating through the container was investigated by examining time histories of projectile velocity and fluid pressure and density. The analysis results were agreed reasonably well compared to those by experiments.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.591-599
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• 2011

This study investigates influencing factors on numerical crash simulation between RC slab and soft projectile using explicit dynamic method. Considered experimental test is the MEPPEN II/4 test, which has been conducted at the end of the years 70' in Germany as one of the numerous experimental test related to design of nuclear power plants. LS-DYNA software is adopted for numerical study, and influencing factors such as constitutive model of concrete, strain rate effect of steel and concrete, support modeling method, etc. are investigated. More reasonable simulation results can be achieved through appropriate consideration of these factors, especially of constitutive model of concrete material since this factor affects most among the investigated factors.

• Computational Structural Engineering
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• v.4 no.1
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• pp.20-27
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• 1991

본 논문에서는 유체-구조 상호작용해석의 일종의 3차원 접수구조물의 진동해석을 효과적으로 수행하기 위한 해석방법을 제시하기 위하여 동적재해석기법을 검토하였다. 접수구조물의 유한구조 상호작용해석 결과는 구조진동의 관심 주파수역에서는 3차원 연성 부가수질량으로 표현되는 관성력으로 나타난다. 따라서 구조질량행렬에 부가수질량 행렬이 더해져서 전체 관성력으로 표현된다. 이 부가수질량을 추가질량으로 보고 재해석기법을 응용하는 방법을 수치실험을 통해 검증하였다. 이 때 재해석기법이 갖추어야 할 조건은 원구조의 질량과 거의 같은 정도의 질량이 추가되고 또한 완전 연성질량이 추가된 경우에도 정확한 해를 주어야 한다는 것이다. 이를 검증하기 위해 직접재해석기법과 섭동법을 이용한 재해석기법으로 4질량 스프링지지구조에 대한 해석을 수행한 결과 직접재해석기법의 응용이 적합함을 쉽게 입증할 수 있었다. 접수구조물의 예로는 3차원 잠수주상체에 대해 접수진동해석을 수행하였으며 그 결과 선체진동해석에 전통적으로 이용되고 있는 2차원 부가수질량과 3차원 수정계수를 사용한 기준차수법에서는 수지모드와 수평-비틔 연성모드와 같이 서로 독립적인 모드에 대해서는 따로 진동해석을 수행해 주어야 하는 단점이 발견되었다. 이 단점을 보완한 각 모드의 3차원 수정계수행렬을 이용한 재해석기법을 도입하여 모드에 상관없이 동시에 해를 구할 수 있었다. 그러나, 이 방법은 3차원 수정계수가 구해져 있는 경우에 한해서만 적용가능하며 실제 선체진동의 경우에는 10Hz 미만의 저차 주선체 진동에 한해서만 적용가능한 방법이다. 고차의 진도옴드에는 3차원 수정계수를 구할 수 없기 때문에 유체-구조 상호작용 해석결과로부터 얻은 3차원 연성 부가수질량을 이용하게 되며 이 때 이 행렬이 접수구조 표면의 전 자유도와 연성되어 있기 때문에 방대한 방정식을 푸어야 하지만 직접재해석기법을 적용함으로써 정확한 해를 구할 수 있었다. 또한 3차원 부가수질량을 이용한 직접재해석기법은 종래의 2차원 부가수질량과 3차원 수정계수를 이용한 방법에 비해 해석시간 면에서도 전혀 불리한 점이 없는 경제적 방법임이 밝혀졌다. 앞으로 Slamming 혹은 수중폭파 등의 충격하중에 의한 천이 구조응답 해석을 위한 효과적인 방법에 대해서도 연구결과를 발표할 계획이다.

• Composites Research
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• v.35 no.3
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• pp.127-133
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• 2022

Polypropylene (PP) has been received great attention as a next-generation high-voltage power cable insulation material that can replace cross-linked polyethylene (XLPE). However, the PP cannot be used alone as an insulation material because of its high elastic modulus and vulnerability to impact, and thus is mainly utilized as a form of a copolymer with rubber phases included in the polymerization step. In this paper, a soft PP-based blend was prepared through melt-mixing of impact PP, polyolefin elastomer, and propylene-ethylene random copolymer. The elastic modulus and impact strength of the blend could properly be decreased or increased, respectively, by introducing elastomeric phases. Furthermore, the blends showed a high storage modulus even at a temperature of 100℃ or higher at which the XLPE loses its mechanical properties. In addition, the blend was found to be effective in suppressing the space charge compared to the pristine PP as well as XLPE.

• Journal of the Society of Naval Architects of Korea
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• v.49 no.3
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• pp.273-279
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• 2012

The concept of the Mobile Harbor had been made recently as a kind of feeder vehicle to transfer a certain amount of container boxes (i.e. 250 TEU at a time) from main ocean container vessels over 5,000 TEU capacity to the container terminal on land. In a harbor a short distance apart from the land, the container loading/unloading operation has to be performed on the main deck of the Mobile Harbor using the container cranes in the state of side-by-side mooring with protection of fenders and robot arms in the gap. Even under the ocean condition of the sea state class 2 or 3, the operation has to be confirmed to be safely performed. In this situation, the floating bodies considering the multiple-body interaction effect also has to be examined whether they might behave safely or not. Especially, this study focuses on the dynamic behavior of the Mobile harbor when a container box is hanged on the crane and the impact load due to the slewing motion is imposed in a certain sea state. The motion response should be controlled within the motion level to assure the safe operation.

• Journal of the Korean Geotechnical Society
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• v.35 no.11
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• pp.25-36
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• 2019

The safety barrier is installed on road embankment to prevent vehicles from falling into road side slope. Among the safety barrier, flexible guardrails are usually installed. The flexible guardrail generally consists of a protection cross-beam and supporting in-line piles. These guardrail piles are installed nearby slope edge of road embankment because the side area of the road is much narrow. The protection cross-beam absorbs impact energy caused by vehicle collision. The pile-soil interaction also absorbs the rest of the impact energy and then, finally, the flexible guardrail system resists the impact load. This paper aims to investigate the pile-soil interaction subjected to impact load using centrifuge model tests. In this study, a single pile was installed in compacted residual soil and loaded under lateral impact load. An impact loading system was designed and developed available on centrifuge tests. Using this loading system, a parametric study was performed and the parameters include types of loading and ground. Finally, the ultimate bearing capacity of supporting pile under impact load was analyzed using load-displacement curve and soil reaction pressure distributions at ultimate were evaluated and compared with previous studies.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.2
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• pp.265-274
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• 2015

The structural safety of nuclear power plant against impact from aircraft crash has been performed so far in two viewpoints such as local behavior and global behavior, and the local behavior has been evaluated using local damage evaluation formulas suggested based on the results of experimental data of RC (Reinforcement Concrete) wall. However, few data have been collected from recent research to evaluate the local behavior and damage of SC (Steel plate reinforced Concrete) wall, which is recently applied to the newly designed nuclear power plant. In this study, local damages of SC wall and RC wall against an idealized aircraft engine projectile impact are evaluated through FE simulation analyses with various wall thicknesses and steel ratio. Through analysis of local collision simulation results of SC and RC wall, the penetration depth of SC wall and RC wall are compared.

• Journal of Navigation and Port Research
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• v.26 no.3
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• pp.323-328
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• 2002

Soil-steel structures have been used for the underpass, or drainage systems in the road embankment. This type of structures sustain external load using the correlations with the steel wall and engineered backfill materials. Buried flexible conduits made of corrugated steel plates for the coastal road was tested under vehicle loading to investigate the effects of live load. Testing conduits was a circular structure with a diameter of 6.25m. Live-load tests were conducted on two sections, one of which an attempt was made to reinforce the soil cover with the two layers of geo-gird. Hoop fiber strains of corrugated plate, normal earth pressures exerted outside the structure, and deformations of structure were instrumented during the tests. This paper describes the measured static and dynamic load responses of structure. Wall thrust by vehicle loads increased mainly at the crown and shoulder part of the conduit. However additional bending moment by vehicle loads was neglectable. The effectiveness of geogrid-reinforced soil cover on reducing hoop thrust is also discussed based on the measurements in two sections of the structure. The maximum thrusts at the section with geogrid-reinforced soil cover was 85-92% of those with un-reinforced soil cover in the static load tests of the circular structure; this confirms the beneficial effect of soil cover reinforcement on reducing the hoop thrust. However, it was revealed that the two layers of geogrid had no effect on reducing the overburden pressure at the crown level of structure. The obtained values of DLA decrease approximately in proportion to the increase in soil cover from 0.9m to 1.5m. These values are about 1.2-1.4 times higher than those specified in CHBDC.