• Current Industrial and Technological Trends in Aerospace
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• v.9 no.1
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• pp.119-129
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• 2011

The soft landing of a lunar lander after the entrance of lunar orbit is an essential prerequisite for the accomplishment of the lander's lunar mission. During the landing process of a lunar lander, efficient shock absorption and stability maintenance are indispensible technology to protect payloads. Therefore, the landing gear is a crucial structural component of a lunar lander, it has to absorb the kinetic energy associated with touchdown and support the static load of the landing module in an upright position. In this paper, various landing gears of lunar landers which are being developed as well as which had been successfully landed on the moon surface are investigated. In the end, the Korean lunar lander, which is being designed for preliminary development model, is presented as an example of the lunar lander development.

• Journal of the Society of Naval Architects of Korea
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• v.35 no.1
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• pp.72-79
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• 1998

Static deformation theory of elastoplastic structures can be applied only if the magnitude of loading is less than the plastic collapse force $F_c$. However, with impact or explosive blast loading, the structure can be subjected to an intense but short-duration force pulse that exceeds the plastic collapse force and initiates structural collapse. In this paper, the dynamic response of a rigid-perfectly plastic cantilever subject to intense impact loading is examined in terms of the plastic collapse force. When a step loading is applied, the motion of the beam is calculated and analyzed through the non-dimensionalization of variables. It is concluded that the motion of a beam can be characterized as a function of the nondimensionalized force parameter, $f{\equiv}F/F_c$, where $F_c$ represents the critical force for plastic collapse. This result is used to the analysis of the beam motion subject to rectangular force pulse.

• Steel and Composite Structures
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• v.22 no.6
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• pp.1359-1389
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• 2016

Buckling and free vibration behavior of a laminated cylindrical panel exposed to non-uniform thermal load is addressed in the present study. The approach comprises of three portions, in the first portion, heat transfer analysis is carried out to compute the non-uniform temperature fields, whereas second portion consists of static analysis wherein stress fields due to thermal load is obtained, and the last portion consists of buckling and prestressed modal analyzes to capture the critical buckling temperature as well as first five natural frequencies and associated mode shapes. Finite element is used to perform the numerical investigation. The detailed parametric study is carried out to analyze the effect of nature of temperature variation across the panel, laminate sequence and structural boundary constraints on the buckling and free vibration behavior. The relation between the buckling temperature of the panel under uniform temperature field and non-uniform temperature field is established using magnification factor. Among four cases considered in this study for position of heat sources, highest magnification factor is observed at the forefront curved edge of the panel where heat source is placed. It is also observed that thermal buckling strength and buckling mode shapes are highly sensitive to nature of temperature field and the effect is significant for the above-mentioned temperature field. Furthermore, it is also observed that the panel with antisymmetric laminate has better buckling strength. Free vibration frequencies and the associated mode shapes are significantly influenced by the non-uniform temperature variations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.9
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• pp.4142-4148
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• 2013

Because of effective fruit growing and management in the slope land, the use of orchard vehicle with lifting utilities has been increased. For this reason the study on the stability of that vehicle for worker's safety is needed. This study is investigated on the stability estimation of orchard vehicle with four wheels and dual rectangular-type lifting utilities which can be moved on the dirt sloping load. Through the multi-body dynamics analysis on the vehicle mechanism, overturning angles of 19.2 and $34.6^{\circ}$ in the right-left and front-rear direction can be calculated. It is determined tractive resistances and required powers of the wheels. And through the finite element analysis on the frame of lifting utility its maximum von-Mises stress is 146 MPa and it is structural stable. Therefore it is known that the orchard vehicle with wheels and lifting utilities has static and dynamic stability.

• International Journal of Highway Engineering
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• v.15 no.1
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• pp.23-36
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• 2013

PURPOSES: The problem under this circumstance is that the erosion not only drops strength of the steel dowel bar but also comes with volume expansion of the steel dowel bar which can reduce load transferring efficiency of the steel dowel bar. To avoid this erosion problem, alternative dowers bars are developed. METHODS: In this study, the bearing stresses between the FRP tube dowel bar and concrete slab are calculated and compared with its allowable bearing stress to check its structural stability in the concrete pavement. These comparisons are conducted with several cross-sections of FRP tube dowel bars. Comprehensive laboratory tests including the shear load-deflection test on a full-scale specimen and the full-scale accelerated joint concrete pavement test are conducted and the results were compared with those from the steel dowel bar. RESULTS: In all cross-sections of FRP tube dowel bars, computed bearing stresses between the FRP tube dowel bar and concrete slab are less than their allowable stress levels. The pultrusion FRP-tube dowel bar show better performance on direct shear tests on full-scale specimen and static compression tests at full-scale concrete pavement joints than prepreg and filament-winding FRP-tube dowel bar. CONCLUSIONS: The FRP tube dowel bars as alternative dowel bar are invulnerable to erosion that may be caused by moisture from masonry joint or bottom of the pavement system. Also, the pultrusion FRP-tube dowel bar performed very well on the laboratory evaluation.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.493-504
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• 2008

This paper deals with the experimental analysis of the flexural behaviour of encased composite beams with hollow core slabs and channels. The shear force between steel beams and hollow core slabs are transferred by channels. Three full-scale specimens were constructed and tested with different steel beam heights, which were compared with those of previous studies. Based on observation of the experiments, the encased composite beams exhibited full shear connection behaviour without any other shear connectors due to their inherent mechanical and chemical bond stress. Experimental results show a behaviour similar to steel-concrete composite beams with classical connectors: elastic and yield domains, great ductility, flexural failure mode (plastic hinge), low relative movement at steel-concrete interface and all specimens failed in a very ductile manner. Consequently, this study enables the validation of the proposed connection device under static loading and shows that it meets modern structural requirements.

• Journal of Korean Society of Transportation
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• v.21 no.4
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• pp.91-101
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• 2003

This study modeled 4-lane highway in three-dimensional virtual reality in order to overcome difficulties of field experiment. and the research subject was placed in a driving simulator. We survey the driver's cognitive characteristics to the alignment changes in the three-dimensional virtual reality highway. Especially, maximizing the identity of driving movements and virtual scenery on the basis of the data obtained by dynamic analysis module. we minimized simulator sickness for the graphic module of driving simulator. And we carried out cognitive evaluation on the basis of adjective words extracted by dictionary and the opinion of specialist. In this study LISREL model was used to detect the causal relation between geometry and safety in cognitive side, and found that geometric change affects the safety of drivers by static and dynamic road safety model in three-dimensional combined alignments. As the result, for constructing safety road. we consider drivers' cognitive characteristics as human factors in road design, and we think that they are very important factors to improve road safety.

• Structural Engineering and Mechanics
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• v.74 no.3
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• pp.395-406
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• 2020

Many prefabricated concrete frame joints have been proposed, and most of them showed good seismic performance. However, there are still some limitations in the proposed fabricated joints. For example, for prefabricated prestressed concrete joints, prefabricated beams and prefabricated columns are assembled as a whole by the pre-stressed steel bar and steel strand in the beams, which brings some troubles to the construction, and the reinforcement in the core area of the joints is complex, and the mechanical mechanism is not clear. Based on the current research results, a new type of fabricated joint of prestressed concrete beams and confined concrete columns is proposed. To study the seismic performance of the joint, the quasi-static test is carried out. The test results show that the nodes exhibit good ductility and energy dissipation. According to the experimental fitting method and the "fixed point pointing" law, the resilience model of this kind of nodes is established, and compared with the experimental results, the two agree well, which can provides a certain reference for elasto-plastic seismic response analysis of this type of structure. Besides, based on the analysis of the factors affecting the shear capacity of the node core area, the formula of shear capacity of the core area of the node is proposed, and the theoretical values of the formula are consistent with the experimental value.

• Journal of the Korean Society of Propulsion Engineers
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• v.2 no.1
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• pp.21-30
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• 1998

Design parameters which used to analyze the stress distribution on the tank wall were defined to develop the propellant tank and obtain optimal values. 1/4 modeling of total tank was selected to calculate the stress distribution with respect to the variation of the support lug location and the tank wall thickness and 1/2 modeling was selected for the stress distributions with respect to the variation of fuel outlet location. Actually, 350psi was applied as static load and 12 gravity as a dynamic load during launching on the internal tank wall. The structural analysis was done with respect to attaching condition of the tank in the satellite. Also the effect of the variation of the propellant outlet location from $0^{\cire}$ to $25^{\cire}$ on the stress distribution was investigated. The equivalent stress distribution and optimal parameters induced from analysis results of the each condition will be used as the fundamental data to design the propellant tank.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.92-105
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• 2000

A study for the structural strength evaluation on the slender doubler plate has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate subjected to the longitudinal in-plane compression, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. Also, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et al. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.