• Journal of the Korean GEO-environmental Society
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• v.24 no.10
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• pp.25-31
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• 2023

Wide tunnels,such as those with high filling, can suffer limited applicability and also reduced structural stability. Therefore, to improve these limitations of precast cut-and-cover tunnel segments, this study proposes rib reinforcement of the vaults of the precast segments. Large-sized experiments assess the effectiveness of the various rib-reinforced precast arch cut-and-cover tunnel structures, and compare them against otherwise similar non-rib-reinforced specimens. The results show that the rib-reinforced precast cut-and-cover segments are suitable for building wide tunnels with high filling.

• 한국지구물리탐사학회:학술대회논문집
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• 2003.11a
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• pp.103-108
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• 2003

In the construction of mountain tunnels, reaction forces of the legs of steel arch supports against the ground are often expected to support the ground being excavated. In these cases, a stress concentration occurs in the ground directly under the support legs. If the bearing capacity of the ground is insufficient or displacement is not effectively constrained, the local failure of the ground under the support legs or settlement of the tunnel supports due to large deformation could result. It is therefore necessary to reinforce the support legs to reduce settlement. As a means of reducing settlement, wing-ribbed steel arch supports are well used. In this study, with the aim of finding a way to quickly reduce the settlement of steel arch support legs, effectiveness of a new type of wing ribs to reinforce steel arch supports was investigated through laboratory testing.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.13 no.1
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• pp.43-49
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• 2005

There are several ways to mold the complex material, and it is divided to vacuum pack mold, compression mold, and hand lay up for a high molecular substance as a basic material. Moreover, it can be divided to general manufacturing (Single form) and mold manufacturing(Mold form) under normal temperature for Firefly. Firefly was manufactured with hand lay up and general manufacturing that using the foam core, glass fabric, and template without mold. However, mold manufacturing that is producing the surface by semi-sandwich using thin foam core and glass fabric then reinforce the inside with spar and rib is on developing. Mold manufacturing can make easy to production, standardize the quality, and possible to mass producing. In this paper, we present the mold producing process for canard aircraft "Firefly", and the problems and solutions during producing Firefly. Moreover, it complements the defect that the problems caused by master manufacturing error when produce several masters of a large part, and make the manufacturing process to be shortened by the replacement from the supplementary plate to the foam that is installed when producing lay up mold.

• Journal of the Korean Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.11-20
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• 2007

The study proposes the method to cancel the scallop to avoid fracture of the circumstance of the scallop at H shape column-to-beam connection and reinforce at beam flange two faces with the cover plates and rib. A total of four specimens were tested to enhance seismic performance of building structure by reducing the frequency of stress concentration and preventing the brittle fracture of scallop. For this purpose, four full-scale test specimens were made and loaded with quasi-static reversed cyclic loading. The main analytical parameters are panel-zone-strength ratio, yield strengths, initial stiffness, total plastic rotation, contribution of each element to total plastic rotation and energy dissipation capability. For the specimens tested under repeated loading, the experimental result was satisfied with seismic performance requirement as the Special Moment Frames (SMF). The analysis results show that all of the test specimens were found to have good performance to 4% story drift and satisfied the criteria for the plastic roation capacity of SMFs that is 0.03 rad. according to the 1997 AISC seismic provision.

• Tunnel and Underground Space
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• v.8 no.3
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• pp.209-225
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• 1998

Recently, Umbrella Arch Method(UAM), one of the auxiliary techniques for tunnelling, is used to reinforce the ground and improve stability of tunnel face. Because UAM combines the advantages of a modern forepoling system with the grouting injection method, this technique has been applied in subway, road and utility tunnel sites for the last few years in Korea. Also, several research results are reported on the examination of the roles of inserted pipes and grouted materials in UAM. But, because of its empirical design and construction methodology, more qualitative and systematic design sequences are needed. Therefore, above sequences using numerical analysis are proposed and, the effects of some design parameters were studied in this research. In order to acco,mplish these objects, first, the roles of pipe and grouting materials, steel-rib and the others in ground improving mechanism of UAM are clarified. Second, the effects of design parameters are investigated through parametric studies. Design parameters are as follows; 1) ground condition, 2) overburden, 3) geometrical formulation of pipes, 4) grouting region and 5) characteristics of pipes.