• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.3
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• pp.55-63
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• 2022

A modular underground arch structure using steel and concrete has been proposed as a structure that has a simple construction process and can effectively resist cross-sectional forces generated during construction and use. Structural behavior of modular underground arch was evaluated about span length less than 15m through 3D structural analysis and test. In general, 2D and 3D structural analysis methods may be applied for structural analysis such as underground arch and tunnels. However, if a 2D or 3D structural analysis method is applied to evaluate the structural safety of a modular underground arch structure, it is difficult to model for structural analysis and it may take an excessively long time to interpret. Therefore, it may not be reasonable as a structural analysis method for considering the structural safety and earth pressure in the design process of a modular underground arch structure. In addition, when a modular underground arch structure is configured for span lengths to which the predetermined cross-section is applicable, it may be reasonable to evaluate only the safety of the structure and cross-section according to the cross-section and load conditions. Therefore, in this study, a structural analysis model using frame elements was proposed for efficient structural safety evaluation. In addition, structural analysis results of the 2D structural analysis model and the simplified analysis model using frame elements were compared, and the structural safety of the modular underground arch structure for a span length of 20m was evaluated with a simplified analysis method.

• Proceedings of the KSR Conference
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• 1999.05a
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• pp.344-351
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• 1999

Stress analysis of bogie frame by using the finite element method has been performed for the various loading conditions according to the UIC (International Union of Railways) Code 615-4. Multiaxial fatigue damage models such as signed von Mises method and typical critical plane theories were reviewed, and multiaxial fatigue analysis program (MUFAP) has been developed. Fatigue analysis of bogie frame under multiaxial loading was performed by using MUFAP and finite element analysis results. The procedure developed in this study is considered to be useful for the life prediction in preliminary design stage of railway components under multiaxial loading conditions. 3-dimensional surface modeling, mesh generation and finite element analysis were performed by Pro-Engineer, MSC/PATRAN and MSC/NASTRAN, respectively, which were installed in engineering workstation.

• Proceedings of the KSR Conference
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• 2000.05a
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• pp.234-241
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• 2000

Stress analysis of the bogie frame by using the finite element method has been performed for the various loading conditions according to the results of vehicle dynamics analysis. Multiaxial fatigue analysis methods such as signed von Mises method, and typical critical plane theories were reviewed, and margin of safety for fatigue is defined. Multiaxial fatigue analysis program to predict the margin of safety of bogie frame under non-proportional loading conditions has been developed by using a commercial command language. Fatigue analysis of bogie frame under multiaxial loading was performed through this program and finite element analysis result. The procedure developed in this study is considered to be useful for the fatigue strength analysis in preliminary design stage of railway components under multiaxial loading condition.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.43-46
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• 2010

본 연구에서는 유체가 담긴 원통형 유체저장탱크의 지진에 의한 좌굴을 수행하였다. 해석에 사용된 유체 저장탱크는 바닥이 앵커로 고정된 3차원 유한요소모델로 모델링 하였으며, 탱크 벽체와 지붕은 쉘 요소로, 지붕보강재는 프레임요소를 사용하여 모델링 하였다. 유체-탱크 모델은 Veletsos와 Shivakumar의 추가 질량법에 근거하여 지진에 의한 유체 압력은 탱크 벽에 수직으로 작용하도록 모델링 하였다. 2007년 일본에서 발생한 지진가속도를 사용하여 범용 유한요소 프로그램인 ABAQUS로 좌굴해석을 수행하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.6
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• pp.581-586
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• 2018

Cast iron manhole lids cause environmental pollution during the manufacturing process, and the work environment is very poor. In addition, if the height of the manhole cover does not match the height of the road surface, it causes considerable inconvenience and safety problems. This study proposes a height - adjustable steel manhole cover that can replace cast iron manhole covers and easily match the road surface with the upper surface of the manhole cover. Structural analysis was performed to grasp the design variable of the structure of the manhole cover, satisfying the required quality performance. To fabricate a manhole cover that satisfies the required load capacity, the optimal design for the U-shaped reinforcement structure was made. The cylindrical shape of the height adjustment part and the low frame were formed by bending the steel sheet into a circular shape and then welding. Reinforcing bars were also made by bending a steel plate. The height adjustment groove was machined by a CNC milling machine. Four prototypes were fabricated and a load bearing test was carried out, and new manhole cover was made reflecting results of the test. In the load bearing test, there was no breakage of the welded part, and deformation occurred mainly at the contact area between the groove and gusset plate. Deformation of 1 to 2.7mm occurred due to a load of 450kN. On the other hand, after removing the load, there was almost no residual deformation, and the load bearing evaluation was judged to be satisfactory because the manhole cover could be disassembled and reassembled.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.75-84
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• 2010

An in-cabinet response spectrum should be generated to perform the seismic qualification of devices and instruments mounted inside safety-related electrical equipment installed in nuclear power plants. The response spectrum is available by obtaining accurate seismic responses at the device mounting location of the cabinet. The dynamic behavior of most of electrical equipment may not be easily analyzed due to their complex mass and stiffness distributions. Considering these facts, this study proposes a procedure to estimate the seismic responses of a structure by a combination of a test and subsequent analysis. This technique firstly constructs the modal equations of the structure by using the experiment modal parameters obtained from the impact test. Then the seismic responses of the structure may be calculated by a mode superposition method. A simple steel frame structure was fabricated as a specimen for the validation of the proposed method. The seismic responses of the specimen were estimated by using the proposed technique and compared with the measurements obtained from the shaking table tests. The study results show that it is possible to accurately estimate the seismic response of the structure by using the experimental modal parameters obtained from the impact test.

• Journal of Korean Society of Steel Construction
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• v.23 no.3
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• pp.357-365
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• 2011

The current trends in steel construction intend to use tapered sections to minimize as much as possible the use of excess material. This can be done by choosing the cross-sections to be as economical as possible, leaving the classical approach of using prismatic members. In addition, it is important to predict the buckling behavior of tapered member with large depth-to-thickness ratio in order to prevent the collapse of PEB system subjected to overloads. An experimental investigation of buckling behavior of tapered beam was presented. The primary test parameter was depth-to-thickness ratio and taper ratio. Using initial stiffness and load-carrying capacity proposed by current provision, the simple plastic hinge method using modified Yoda's model and finite element analysis, the prediction of a moment-rotation curve of linearly tapered member was presented. Moreover, comparisons between analytical and experimental data for moment-rotation curves were accomplished.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3B
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• pp.264-273
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• 2009

For IEEE 802.15.3 HR-WPAN, we propose the DABL algorithm that PNC can allocate the channel times to the DEV in super frame in order that system frame throughput is increased and the delay is decreased. In detail, the DABL algorithm allows to dynamically allocate channel time as well as to adaptively apply the modulation and coding scheme based on the link quality of the DEV. In addition, due to the facts that QoS is quite different depending on service types, we provide the DABL algorithm taking into account RT(Real Time) traffic and Non-RT traffic respectively. Finally, we show simulation results of the DABL algorithm compared to the conventional algorithm that the PNC equally allocates channel times to the DEV regardless of the link quality of the DEV.

• Land and Housing Review
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• v.5 no.4
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• pp.305-314
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• 2014

The technology-intensive unit modular method of factory production method is attracting attention by the limit of the labor-intensive and field centered wet construction method. In recent years, the unit modular method has been applied to the construction of schoolhouse and BOQ(bachelor offices' quarters), dormitories, etc. But the modular method still is not used in housing construction by the lack of verification of resident performance and construction cost. Therefore, this study analyzed the economics of modular house to vitalize the constructed residential building by modular method and to develop the modular method. According to the study results, the construction cost of the modular house was analysed more about 6.2% expensive than that of the existing housing. However, if the construction duration of modular house is shortened or the productivity of modular house is increased, the construction cost of modular house will be similar to the that of the existing house.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1A
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• pp.58-64
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• 2009

In this paper, we propose an dynamic random channel allocation scheme increasing probability of channel acquisition and reducing delay by limiting the number of minimum RCHs(Random CHannels) as an optimal factor $\beta$. The MAC protocol of HIPERLAN/2 is based on TDMA/TDD and MT(Mobile Terminal) can obtain chance of traffic transmission through channel competition in RCH period. And AP(Access Point) can dynamically schedule the number of RCHs based on the number of the collision in each RCH of the previous frame. Therefore, the proposed scheme increases a probability of channel acquisition and reduces delay by means of guaranteeing the number of minimum RCHs. With a practical Internet traffic, it is concluded that by the proposed scheme the delay reduction of the order of 19% and slightly better throughput are obtained compared to the conventional algorithm.