• 한국지반환경공학회 논문집
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• 제18권10호
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• pp.5-14
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• 2017

In recent years, world has witnessed many man-made activities related to both above and underground blasts. Details on behaviour of shallow foundations subjected to blast loads and induced liquefaction is scarce in literature. In this paper, typical shallow strip foundation in saturated cohesionless soils subjected to both above and underground blasting have been simulated by using finite difference based numerical model FLAC3D. Peak particle velocity (PPV) has been obtained to propose critical values for which bearing capacity failure for shallow foundations with soil liquefaction can occur. Typical results for pore pressure ratio (PPR) for various scaled distances are compared to PPR values obtained by using empirical equation available in literature which shows good agreement. Critical design values obtained in the present study for PPV and PPR to estimate the scaled distance, bearing capacity failure and liquefaction susceptibility can be used effectively for design of shallow strip foundation in cohesionless soil subjected to both above and under ground blast loads.

• 터널과지하공간
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• 제11권2호
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• pp.96-108
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• 2001

NATM 터널의 콘크리트라이닝은 계획, 지반조사, 지반-라이닝 상호작용해석, 시공, 관찰, 시공중 수정 등의 과정을 거쳐 시공된다. 따라서, 설계자는 라이닝의 여러 기능, 시공과정, 지반조건 등을 고려하여야 한다. NATM 터널 콘크리트라이닝 설계시 지반조건이 열악하거나 숏크리트의 부식 등으로 1차 지보재가 지보능력을 상실할 경우에 대비하여야 한다. 그러나, 암반이완하중과 잔류수압의 크기, 형태 및 산정방법이 설계자에 따라 다양하게 적용되고 있는것이 현실이다. 본 논문에서는 NATM 터널 콘크리트라이닝 설계시 적용할 수 있는 암반이완하중 산정 법들에 대하여 고찰하고, 설계시 국내에서 주로 적용하는 다양한 암반하중과 잔류수압모델을 조합하여 구조해석을 실시한 후 콘크리트라이닝에 발생 하는 부재력의 크기를 비교하였으며, 적절한 하중조합을 제시하였다.

• 전기기술인
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• 제228권8호
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• pp.43-48
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• 2001

우리나라에서는 3 Θ 4w 배전방식을 채택하고 있는데 최근에는 컴퓨터 등 OA 기기 사용증가로 이때 발생하는 영상분 고조파에 의하여 중성선에 상전류 보다 큰 전류가 흐르게 된다. 고조파에 의한 중전선 과전류는 케이블, 변압기, 과열소손, 변압기, 발전기 출력저하, 역률저하, 전력손실 증가, ELB, MCCB 오동작, 유도장해, 중성선 대지전위 상승 등 심각한 장애를 일으키고 있다.

• Structural Engineering and Mechanics
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• 제58권5호
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• pp.799-823
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• 2016

A finite element model for the non-linear dynamic analysis of a reinforced concrete (RC) containment shell of a nuclear power plant subjected to extreme loads such as impact and earthquake is presented in this work. The impact is modeled by using an uncoupled approach in which a load function is applied at the impact zone. The earthquake load is modeled by prescribing ground accelerations at the base of the structure. The nuclear containment is discretized spatially by using 20-node brick finite elements. The concrete in compression is modeled by using a modified $Dr{\ddot{u}}cker$-Prager elasto-plastic constitutive law where strain rate effects are considered. Cracking of concrete is modeled by using a smeared cracking approach where the tension-stiffening effect is included via a strain-softening rule. A model based on fracture mechanics, using the concept of constant fracture energy release, is used to relate the strain softening effect to the element size in order to guaranty mesh independency in the numerical prediction. The reinforcing bars are represented by incorporated membrane elements with a von Mises elasto-plastic law. Two benchmarks are used to verify the numerical implementation of the present model. Results are presented graphically in terms of displacement histories and cracking patterns. Finally, the influence of the shear transfer model used for cracked concrete as well as the effect due to a base slab incorporation in the numerical modeling are analyzed.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2011년도 정기 학술대회
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• pp.324-327
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• 2011

The design requirement for ground mounted sign structures are fairly well defined in the AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaries, and Traffic Signals and consists of applying an equivalent pseudo-dynamic loading to account for the dynamic effects of wind loads and ignores the dynamic effect due to moving vehicle loads. This design approach, however, should not be applied to the design of bridge mounted sign structures because ignoring the dynamic effects of the moving vehicle loads may produce non-conservative results, since the stiffness of the bridge structure can greatly influence the behavior. Not enough information is available in the literatures which provide guide lines to include the influence of moving vehicles in the design of the bridge mounted sign structures. This paper describes a theoretical methodology, Bridge-Vehicle Interaction Element, which can be utilized to account for the dynamic effect of moving vehicles. A case study is also included where this methodology was successfully applied. It was concluded that the bridge-vehicle interaction finite element developed can provide a more accurate representation of the behavior of bridge mounted sign structures. The result of these analysis enabled development of simple and effective retrofitting scheme for the existing support system of bridge-mounted-structure.

• 대한건축학회논문집:구조계
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• 제35권10호
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• pp.235-243
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• 2019

In South Korea, millions of poultry have died due to repeated heat waves every year. The purpose of this study is to analyze the characteristics of heating and cooling loads of chicken houses in Korea and to present an effective insulation and ventilation measures to minimize the damage of poultry due to summer heat wave and to save energy in chicken houses in winter. The heating and cooling loads of standard chicken house were calculated. As a result of the calculation of maximum heating load based on the minimum ventilation rate in winter, the outdoor air temperature requiring heating was $6{\sim}7^{\circ}C$ to keep the indoor air temperature of chicken houses as $24^{\circ}C$. The peak cooling load of chicken houses was mostly taken by the heat generated by chickens and the heat gain due to ventilation. The heat gain through building envelopes was as small as neglectable. Most of chicken houses is usually cooled by gigantic forced ventilation in summer in Korea. When the chicken houses are cooled by electric cooling machine such as cooler or air conditioner, it is more effective to keep minimum ventilation rate to reduce the maximum cooling load. To lower the temperature of supplying water to cooling pad, it is recommended to use the underground water below 10 meters from the ground if there is abundant underground water.

• International Journal of Naval Architecture and Ocean Engineering
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• 제12권1호
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• pp.743-754
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• 2020

This study provides an insight of the nonlinear behavior of the Offshore Wind Turbine (OWT) structure using the distributed plasticity approach. The fiber section beam-column element is applied to construct the finite element model. The accuracy of the proposed model is verified using linear analysis via the comparison of the dynamic characteristics. For collapse risk assessment of OWT, the nonlinear effects considering the earthquake Incident Angle (IA) have been evaluated first. Then, the Incremental Dynamic Analysis (IDA) has been executed using a set of 20 near-fault records. Lastly, fragility curves are developed to evaluate the vulnerability of structures for different limit states. Attained results justify the accuracy of the proposed approach for the structural response against the ground motions and other environmental loads. It indicates that effects of static wind and wave loads along with the earthquake loads should be considered during the risk assessment of the OWT structure.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2022년도 추계학술발표대회
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• pp.815-817
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• 2022

This paper is about the development of an automatic stair climbing trolley for carrying loads without manpower. The design of tri-wheeled structure and center of mass enable the trolley to move on flat ground and also to ascend stairs by self-balancing. The overall design enables the trolley to avoid collision to walls when the trolley rotates on domestic landings. When the camera recognizes the stair, the sensor measures distance from the trolley to the stair. Then the trolley can move to align itself in the middle of the stair and it starts climbing. It can ascend to a specific floor based on the floor number entered by the user. As a result, the automatic stair climbing trolley is expected to help humans by protecting from accidents of dropping loads and saving their power. It is also expected to use for various purposes such as delivering packages, moving and carrying heavy loads in buildings without elevator.

• 터널과지하공간
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• 제20권1호
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• pp.58-64
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• 2010

지반과 터널라이닝의 상호작용을 고려한 GLI모델은 기존의 Terzaghi 이완하중과 골조모델을 이용한 방법에 비해 터널의 2차라이닝(콘크리트라이닝)에 작용하는 지반하중을 합리적으로 경감할 수 있음이 입증된 바 있다. 이에 본 연구에서는 기존의 골조모델을 이용하여 설계된 OO선O공구의 콘크리트라이닝에 대해 GLI모델을 도입한 현장설계를 통해 경제성 및 시공성을 개선하였다. 다양한 안전측 고려사항에도 불구하고 철근량의 약 50%가 감소하여 철근자재비를 감소시킬 수 있었고 적정한 철근간격을 확보하여 콘크리트 밀실충전이 용이하였다. 지반조건이 불량한 터널일 수록 더 큰 철근량 절감효과가 있었으며, 이는 Terzaghi 이완하중이 불량한 지반에서 과도하게 산정되기 때문이다.

• 지질공학
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• 제30권2호
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• pp.131-145
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• 2020

연약지반 상에 도로성토를 시공할 경우 연약지반에는 편재하중이 작용하게 되어 연약지반의 측방유동이나 활동파괴가 종종 발생하게 된다. 본 연구에서는 연약지반에 설치되는 교대말둑기초의 안정성과 말뚝의 거동특성을 파악하는 것이다. 지반의 측방유동으로 인하여 말뚝에 작용하는 수평하중에 대한 기존 연구자들의 연구내용을 파악하고 유한요소해석을 수행하여 교대말뚝기초의 거동특성과 보강효과를 확인하여 측방유동을 받는 교대말뚝기초의 거동을 연구하였다. 압밀도 분석 결과, 압밀 단계에 따라 연약지반 강도증가율에 의해 연약지반의 강도정수인 점착력은 약 1.1~1.8배 증가하였다. 측방유동 검토 결과, 허용수평변위 기준은 3.8 cm를 사용하는 것이 경제적으로나 시공적인 면에서 타당한 것으로 판단되나, 구조물의 중요도 및 지반의 불확실성 등을 고려하여 시공 시 계측을 실시하고 그에 따른 측방유동에 대한 철저한 안전관리가 이루어져야 할 것으로 판단된다.