• Title/Summary/Keyword: 시공하중

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Calculations of Flat Plate Deflections Considering Effects of Construction Loads and Cracking (시공하중 및 균열 효과를 고려한 플랫 플레이트의 처짐 산정)

  • Kim, Jae-Yo;Im, Ju-Hyeuk;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.21 no.6
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    • pp.797-804
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    • 2009
  • The structural designs of RC flat plates that have insufficient flexural stiffness due to lack of support from boundary beams may be governed by serviceability as well as a strength criteira. Specially, since over-loading and tensile cracking in early-aged slabs significantly increase the deflection of a flat plate system under construction, a construction sequence and its impact on the slab deflections may be decisive factors in designs of flat plate systems. In this study, the procedure of calculating slab deflections considering construction sequences and concrete cracking effects is proposed. The construction steps and the construction loads are defined by the simplified method, and then the slab moments, elastic deflections, and the effective moment of inertia are calculated in each construction step. The elastic deflections in column and middle strips are magnified to inelastic deflections by the effective moment of inertia, and the center deflection of slab are calculated by the crossing beam method. The proposed method is verified by comparisons with the existing test result and the nonlinear analysis result. Also, by applications of the proposed method, the effects of the slab construction cycle and the number of shored floors on the deflections of flat plates under construction are analyzed.

Field Tests for Vertical Loads Acting on Embankment Piles (성토지지말뚝에 작용하는 연직하중에 대한 현장시험)

  • 이승현;이영남;홍원표;이광우
    • Journal of the Korean Geotechnical Society
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    • v.17 no.4
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    • pp.221-229
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    • 2001
  • 연약지반의 측방유동으로 인한 피해가 예상되는 국내 현장에 성토지지말뚝공법을 적용하기 위한 연구의 일환으로 실제 현장에서 성토지지말뚝이 발휘하는 효과를 규명하기 위한 현장시험이 계획되었다. 본 현장시험은 직경 40.64cm의 강관말뚝을 3본씩 총 4여로 시공하고, 각 열의 줄말뚝은 콘크리트캡보로 연결한 다음 총 8m까지 성토하였다. 현장시험은 총 2회에 걸쳐 수행하였으며, 성토지지말뚝의 하중분담효과를 확인하기 위해 하중계, 토압계, 지중경사계, 그리고 침하판을 이용한 계측을 실시하였다. 또한 계측결과를 제안이론식과 비교분석하였다. 이러한 연구 결과 성토지지말뚝을 시공할 경우 성토지지말뚝 위 성토지반속에 발달하는 지반아치에 의해 대부분의 성토하중이 말뚝으로 전이됨을 확인하였고, 말뚝캡보의 설치 간격이 좁을수록, 그리고 성토고가 높을수록 성토지지말뚝의 하중분담효과가 더 커지게 됨을 확인할 수 있었다. 또한 설계시 성토지지말뚝의 설치범위를 합리적으로 결정하기 위해서는 성토지지말뚝이 성토사면의 사면안정효과에 미치는 영향을 고려해야 함을 알 수 있었으며, 제안이론식이 현장상태의 성토지지말뚝에 합리적으로 적용될 수 있음을 입증하였다.

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A Study on Construction Condition of Modular System by Structural Analysis of Construction Stage (시공단계 구조해석을 통한 적층형 모듈러주택의 시공조건 검토)

  • Jo, Min-Joo;Kim, Jong-Sung;Yu, Seong-Yong;Choi, Ki-Bong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.2
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    • pp.143-150
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    • 2015
  • At present, the actual condition is that Korean modular structures are limited to a low rise detached house and military barracks. And there is no standardized structural design method of stacked modular structure. Accordingly, in general, they don't review impact force in the stage of stacking and installing a module, the effect which wind load has on a structure in the stage of lifting, and inertial force occurring in the stage of lifting or transporting a module in the process of constructing a structure. Therefore, this study investigated the construction method of modular system to be studied in stages, and decided on the position to which load was applied and boundary condition in structural analysis at each construction stage. Besides, inertial force according to each speed was calculated in the lifting and wheeled transport of module. And we calculated impact load according to lifting speed in module stacking and installation work and wind load due to instantaneous wind speed in the installation work by lifting. On the basis of the suggested method, in the modular system to be studied, it carried out review of structure by changing determining conditions of load being applied by construction stage, such as in the stage of lifting, in the stage of transport, and in the stage of installation, and drew construction conditions securing stability structurally.

Structural Performance of Double Rip Decks Reinforced with Inverted Triangular Truss Girders (역삼각 트러스 거더로 보강된 더블 골 데크 성능 평가)

  • Son, Hong-Jun;Kim, Young-Ho;Chung, Kyung-Soo;Kim, Dae-Jin
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.6
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    • pp.559-566
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    • 2017
  • This paper proposes a new composite deckplate system reinforced with inverted triangular truss girders(called 'D Deck'), which does not require the use of temporary supports at construction stage. The proposed system retains increased stiffness and strength while keeping the absolute floor height change to a minimum level and can be utilized as floor systems of various types beam members such as the conventional wide-flange and U-shaped composite beams. In order to evaluate the performance of the proposed system, five specimens with a span of 5.5 m were fabricated and tested under field loading conditions consisting of several intermediate steps. The load-deflection curves of each specimen were plotted and compared with the nonlinear three-dimensional finite element analysis results. The comparison showed that the effective load sharing between the truss girders and floor deck occurs and the maximum deflection under construction stage loading is well below the limit estimated by the provisions in Korea Building Code.

Tunnel-Lining Analysis in Consideration of Seepage and Rock Mass Behavior (투수 및 암반거동을 고려한 터널 라이닝의 거동 분석)

  • Kong, Jung-Sik;Choi, Joon-Woo;Nam, Seok-Woo;Lee, In-Mo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.5C
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    • pp.359-368
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    • 2006
  • After construction, time-variant seepage and long-term underground motion are representative factors to understand the abnormal behavior of tunnels. In this study, numerical models have been developed to analyze the behavior of tunnels associated with seepage and long-term underground motion. Possible scenarios have been investigated to establish causes-and-results mechanisms. Various parameters such as permeability of tunnel filter, seepage condition, water table, long-term rock mass load, size of damaged zone due to excessive blasting have been investigated. These are divided into two sub-parts depending on the tunnel type and major loading mechanisms depending on the types. For the soft ground tunnels, the behavior associated with seepage conditions has been studied and the effect of permeability change in tunnel-filter and the effect of water-table change which are seldom measurable are investigated in detail. For the rock mass tunnels, tunnel behavior associated with the visco-plastic behavior of rock mass has been studied and the long-term rock mass loads as a result of relaxation and creep have been considered.

Investigation on Support Mechanism of Geogrid-Encased Stone Columns in Soft Ground (연약지반에 시공되는 지오그리드 감쌈 스톤컬럼의 하중 지지 메카니즘에 관한 연구)

  • Yoo, Chung-Sik;Kim, Sun-Bin
    • Journal of the Korean Geotechnical Society
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    • v.24 no.12
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    • pp.93-101
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    • 2008
  • This paper presents the results of numerical investigation on support mechanism of geogrid-encased stone columns for use in soft ground improvement. A number of cases were analyzed using a 3D stress-pore pressure coupled model that can effectively model construction sequence and drainage as well as reinforcing effects of geogrid-encased stone columns. The results indicated that the geogrid encasement provides additional confinement effect that reduces vertical stress in the soft ground, thus resulting in less excess pore water pressures and associated settlement. Also revealed was that such a confinement effect depends on encasement length and stiffness of geogrid. It is also shown that there exist critical encasement length and stiffness of geogrid for a given condition.

Effect of Shotcrete Lining Adherence on Load Carrying Capacity of Lining (숏크라트 라이닝 층간 부착성이 라이닝의 하중지지력에 미치는 영향)

  • Yoo, Chung-Sik;Kim, Sun-Bin;Bae, Gyu-Jin;Shin, Hyu-Soung
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.8 no.1
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    • pp.41-51
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    • 2006
  • This paper concerns the effect of lining interface adherence on the lining's load carrying capacity. A series of reduced scale laboratory tests and finite element anlayses were carried out with the aim of gaining insight into the effect of shotcrete lining adherence on the load carrying capacity of double shell lining. The results indicated among other things that the load carrying capacity of a double shell tunnel is significantly affected by the adherence between layers. Also revealed was that for cases with low lining layer adherence stress concentration may occur due to relative movement between the lining layers with this trend being more pronounced with increasing tunnel cover depth. Practical implications from the results of this study are discussed in great detail.

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Behaviour of a 2-arch Tunnel in a Large-scale Model Test (대규모 실내 모형실험을 통한 2-ARCH 터널의 거동 분석)

  • Lee C.J.;Kim J.S.;Ryu N.Y.;Lee S.D.;Jeong K.H.;Yang J.W.
    • 한국터널공학회:학술대회논문집
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    • 2005.04a
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    • pp.282-291
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    • 2005
  • 사암 및 이암을 기반암으로 하는 산악지역에 건설되는 2-아치 (2-arch) 터널의 거동을 터널설계 단계에서 분석하기 위하여 대규모 실내 모형실험을 실시하였다. 터널이 시공될 예정인 지반과 유사한 지질공학적 특성을 가지는 콘크리트 블록을 이용하여 모형지반을 조성하였다. 모형실험은 중앙터널 (pilot tunnel) 굴착을 포함한 여러 단계의 굴착과정으로 구분하여 실시되었다. 또한 터널 .공용기간 중 터널의 거동을 연구하기 위하여 터널굴착 완료 후 상재하중을 작용시켰다. 실험결과에 의하면 대부분의 지반변위는 중앙터널 굴착에 의해 발생했으며, 그 이후 터널 굴착단계에서의 변위발생은 미미한 것으로 나타났다. 또한 대부분의 지중변위는 0.25D 이내의 범위에서 발생하였다. 여기서 D 는 터널의 폭이다. 한편 실험결과를 분석하여 경암에 시공되는 2-아치 터널의 중앙벽체(centre pillar)에 작용하는 하중에 대한 경험적인 공식을 제시하였다. 터널시공 완료 후 공용기간 중 상재하중이 작용할 경우 그 크기에 따라서는 터널굴착에 의해 발생한 것보다 더 큰 지중변위가 발생할 수 있는 것으로 분석되었다. 터널의 거동은 중앙벽체의 강성에 큰 영향을 받는 것으로 나타나 이를 터널설계에 반영하여 중앙벽체의 강성을 증가시켰다. 현재 터널시공을 위한 사전작업이 진행 중에 있으며, 터널의 굴착은 2005년 하반기에 실시될 예정이다.

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Micro-Cracks Control of LB-DECK Using Polymer Cement Concrete (폴리머 시멘트 콘크리트를 이용한 LB-DECK의 미소균열 제어)

  • Lho, Byeong-Cheol;Choi, Jong-Yun;Cho, Gyu-Dae;Choi, Jong-Gwon
    • Journal of the Korea Concrete Institute
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    • v.24 no.2
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    • pp.103-109
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    • 2012
  • Micro-cracks with a width less than 0.1 mm in precast concrete panels do not cause structural problem, but they can cause problems in long term durability and concrete surfaces aesthetic, requiring additional repair costs. In this paper, polymer cement concrete is used to increase flexural tensile strength and to prevent micro-cracks due to construction loads on LB-DECK panels. Using 5% polymer-cement ratio, the panel crack moment is increased by improving flexural tensile strength and controlling visible micro-cracks during construction stage of LB-DECK.