• Title/Summary/Keyword: 하중감소기법

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Analysis of pillar stability according to reinforcement method for very near parallel tunnel (초근접 병렬터널 필라부 보강공법에 따른 안정성 분석)

  • Jo, Young-Seok;Kim, Yun-Hee;Hong, Ji-Yeon;Kim, Dong-Gyou;Kim, Bumjoo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.23 no.2
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    • pp.119-131
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    • 2021
  • In general, the stress is concentrated on the pillar of very near parallel tunnel (VNPT), and the pillar has been reinforced by using steel-wires to maintain the stability of the tunnel. However, since the strength of the pillar decreases in the soil layer, the reinforcing pillar with the steel-wires is insufficient for tunnel stability. In this study, the laboratory tunnel experiment was conducted to examine the reinforcement effect for a new method, of which the pillar of VNPT is strengthened by using steel-pipes. As a result, against overburden stress, the bearing capacity of the steel-pipe reinforcement was 22% greater than that of the steel-wire reinforcement. In using the Particle Image Velocimetry method, the analysis shows that the steel-pipe reinforcement forms a more favorable condition of which uniformly the overburden load acts on the VNPT and the pillar than the steel-wire reinforcement. Based on the results, the steel-pipe reinforcement is expected to bring a more positive effect on tunnel stability than the steel-wire reinforcement.

The Optimal Configuration of Arch Structures Using Force Approximate Method (부재력(部材力) 근사해법(近似解法)을 이용(利用)한 아치구조물(構造物)의 형상최적화(形狀最適化)에 관한 연구(研究))

  • Lee, Gyu Won;Ro, Min Lae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.13 no.2
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    • pp.95-109
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    • 1993
  • In this study, the optimal configuration of arch structure has been tested by a decomposition technique. The object of this study is to provide the method of optimizing the shapes of both two hinged and fixed arches. The problem of optimal configuration of arch structures includes the interaction formulas, the working stress, and the buckling stress constraints on the assumption that arch ribs can be approximated by a finite number of straight members. On the first level, buckling loads are calculated from the relation of the stiffness matrix and the geometric stiffness matrix by using Rayleigh-Ritz method, and the number of the structural analyses can be decreased by approximating member forces through sensitivity analysis using the design space approach. The objective function is formulated as the total weight of the structures, and the constraints are derived by including the working stress, the buckling stress, and the side limit. On the second level, the nodal point coordinates of the arch structures are used as design variables and the objective function has been taken as the weight function. By treating the nodal point coordinates as design variable, the problem of optimization can be reduced to unconstrained optimal design problem which is easy to solve. Numerical comparisons with results which are obtained from numerical tests for several arch structures with various shapes and constraints show that convergence rate is very fast regardless of constraint types and configuration of arch structures. And the optimal configuration or the arch structures obtained in this study is almost the identical one from other results. The total weight could be decreased by 17.7%-91.7% when an optimal configuration is accomplished.

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