• Title/Summary/Keyword: WAS 슬래브

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Dynamic Characteristic of Post-tensioned Void Slab (포스트텐션 중공슬래브의 동적 특성)

  • Yoon, Sung-Won
    • Journal of Korean Association for Spatial Structures
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    • v.12 no.3
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    • pp.89-95
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    • 2012
  • Post-tensioned void slab is frequently used for improving the deflection and sound proofing. Two one story 8m spanned structures were built. One structure applied post-tensioned solid slab, but the other did post-tensioned void slab. Dynamic characteristics, which is natural frequency and damping ratio, was compared between that of solid slab and void slab before and after post tension. The natural frequency of void slab was greater than that of solid slab before and after post tension. It was shown that damping ratio of solid slab and void slab was almost same at two stages.

Slab Construction Load Distribution in a Multistory-shored RC Structure System with Different Slab Thickness (슬래브 두께가 다른 다층지지 RC 구조 시스템에서의 슬래브 시공 하중 분포)

  • Sang-Min Han;Jae-Yo Kim
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.28 no.2
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    • pp.17-26
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    • 2024
  • In recent times, accidents involving structural elements, formwork, and shore have been persistently occurring during concrete pouring, especially in multi-story reinforced concrete (RC) structures. In previous studies, research on construction load analysis was mainly conducted for cases where the thickness of all slabs is constant. However, when the thickness of some slabs is different, the variation in the stiffness of slab cross-sections can lead to different distributions of construction loads, necessitating further investigation. In this study, the slab thickness was set as a variable, and the analysis of the distribution of construction loads was conducted, taking into account the influence of changes in slab thickness on the concrete stiffness and structure. It was confirmed that not only the concrete material stiffness but also the slab cross-section stiffness should be considered in the estimation of construction loads when the slab thickness changes. As the slab thickness increases, the maximum construction load and maximum damage parameter on the layer with increased thickness significantly increase, and it was observed that a thicker slab results in a higher proportion of construction load.

Estimation Method of Residual Performance for Hollow Slab at Elevated Temperature (고온에 노출된 중공슬래브의 잔존성능 추정방법)

  • Choi, Hyun-Ki;Chung, Joo-Hong;Choi, Chang-Sik
    • Journal of the Korea Concrete Institute
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    • v.26 no.5
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    • pp.643-650
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    • 2014
  • Generally, the reinforced concrete slab has great fire resistance performance because concrete has excellent thermal material properties under fire. But, in the case of hollow slab, it will be expected that hollow slabs have different temperature distribution and fire endurance performance compare to reinforced concrete slab. Because hollow slab has internal void space that occurs decreasing regenerative effect of concrete and formation of internal air layer. Evaluation method for fire resistance performance of hollow slabs was proposed using $wickstr{\ddot{o}}m^{\prime}s$ method. For the casual use of evaluation, simplified method was proposed which was limited to solid slab and donut type hollow slab which was developed by authors of this research paper. Also, verification on proposed method was performed by comparing results of fire experiment for hollow slab and evaluation results. Proposed method of the results of this study was possible to predict the residual strength and temperature distribution of slabs under fire.

Experimental Analysis of Prestressed Approach Slab Behavior (프리스트레스가 도입된 접속슬래브의 실험적 거동 분석)

  • Park, Hee-Beom;Eum, In-Sub;Kim, Seong-Min
    • International Journal of Highway Engineering
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    • v.12 no.4
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    • pp.157-164
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    • 2010
  • This research was conducted to analyze the behavior of Single-PTAS (Single Post-Tensioned Approach Slab) under tensioning and environmental loads by performing field tests when the demonstration Single-PTAS was being constructed. The temperature measurement sensors were installed at different depths, and the displacements in the approach slab under environmental loads and tensioning were measured using displacement transducers. As an experimental result, an abrupt change in the longitudinal displacement due to tensioning was not observed. The daily temperature change in the approach slab was negligible where the depth is over about 35cm. The temperature gradient in the approach slab adjacent to bridge was smaller than that adjacent to pavement. The patterns and magnitudes of vertical displacements were directly related to the temperature gradient at the measuring location. The behavior of Single-PTAS was very similar to that of concrete pavement. Therefore, a new design methodology for approach slabs is needed to include the pavement concept and to overcome drawback of current design procedures based on the simple beam concept.

Numerical Analysis off-Shape Cracking in Jointed Concrete Pavements (줄눈콘크리트 포장의 T형 균열 발생 원인 수치 해석)

  • Yun, Dong-Ju;Seo, Young-Guk;Kim, Seong-Min
    • International Journal of Highway Engineering
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    • v.11 no.2
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    • pp.141-149
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    • 2009
  • This study was conducted to investigate the causes that induce the T-shape cracks at the joints in the jointed concrete pavements(JCPs). The finite element models of JCP including dowel bars were developed and the stress distribution in the slab was investigated under environmental loads. To investigate the effect of dowel bars on the transverse stresses at the joints that induce the T-shape cracks, the slab curling behavior was analyzed with and without dowel bars. In addition, the stress concentration was investigated when the dowel bar was not installed at the mid-depth of the slab. The results of this study showed that the transverse stresses were not affected by the dowel bars if the dowel bars were installed at the mid-depth of the slab. However, if the dowel bars were not installed at the mid-depth, the transverse stresses were concentrated at the dowel bar locations when the slab curled. The stress concentration was dependent on the contact characteristics between the dowel bar and concrete, and was significantly large when the dowel bar not installed at the mid-depth was located far from the edge of the slab. Therefore, to mitigate T-shape cracking in JCP, dowel bars should be very carefully installed and leveled at the proper locations.

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Development of a Nondestructive Seismic Technique for Flexural Rigidity of Concrete Track as Slab Displacement Index (콘크리트 슬래브궤도의 휨강성 평가를 위한 비파괴 탄성파 기법의 개발)

  • Cho, Mi-Ra;Joh, Sung-Ho;Lee, Il-Wha
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.28 no.6D
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    • pp.905-913
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    • 2008
  • Recently, concrete tracks are introduced into high-speed railroads as an alternative to ballast tracks. Concrete tracks are superior to ballast tracks in the aspect of durability, maintenance and safety. However, deteriorated stiffness of railroad bed and settlement of soft ground induced by trapped or seepage water lead to problems in safety of train operation. In this research, flexural rigidity of concrete tracks was employed as an index of track displacement and a new seismic technique called FRACTAL (Flexural-Rigidity Assessment of Concrete Tracks by Antisymmetric Lamb Waves) method was proposed to delineate flexural rigidity of concrete tracks in a 2-D image. In this paper, to establish theoretical background, parametric research was performed using numerical simulations of stress-wave tests at concrete tracks. Feasibility of the FRACTAL technique was proved at a real concrete track for Korean high-speed trains. Validity of the FRACTAL technique was also verified by comparing the results of impulse-response tests performed at the same measurement array and the results of DC resistivity survey performed at a shoulder nearby the track.

Strengthening Effects of Slabs by Aramid Fiber Sheet (아라미드섬유 쉬트에 의한 슬래브의 보강효과)

  • Yeon, Kyu-Seok;Kang, Young-Sug;Kim, Hyung-Woo;Lee, Youn-Su;Kim, Nam-Gil
    • Magazine of the Korea Concrete Institute
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    • v.11 no.2
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    • pp.105-113
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    • 1999
  • This study was conducted to evaluate the structural behaviors of Aramid fiber sheet reinforced slabs. Seven concrete slabs with $45{\times}8.5{\times}200cm$ were made for this experiment one slab with out being reinforced completely loaded until failure and the maximum load was obtained from this test. 70% of the maximum load was applied to 3 Aramid fiber sheet reinforced slabs after cracking and to the rest of 3 Aramid fiber sheet reinforced slabs without loading and cracking. Test results shows that maximum loading flexural rigidity and ductility for the Araimid fiber sheet reinforced slabs after initial cracking are similar as those for the Armied fiber sheet reinforced slabs without loading and cracking.

Experimental Analysis of Curling Behavior of Concrete Slabs on Grade under Temperature Loading and Underlying Layers' Effects (지반위에 놓인 콘크리트 슬래브의 온도하중 하의 컬링 거동 및 하부층 영향 실험적 분석)

  • Kim, Seong-Min;Park, Hee-Beom
    • International Journal of Highway Engineering
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    • v.10 no.4
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    • pp.171-180
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    • 2008
  • This study was conducted to analyze the curling behavior of concrete slabs on grade under temperature loading through the laboratory tests and to investigate the effects of the support conditions of underlying layers on the curling behavior of the slab on grade systems. For the laboratory tests, the concrete slabs were fabricated and the temperature measurement sensors were installed. The temperature loading was applied intentionally and the time histories of the vertical displacements of the slab at several different positions were measured. One-layered underlying layers were made using different materials and different thicknesses. Two-layered underlying layers were also made to have the same composite stiffness each other, but the material of the upper layer was designed to be different The experimental analysis results showed that the trend of the displacement time histories of the slab was basically the same as that of the temperature gradient time histories. The characteristics of the curling behavior of the slab were analyzed by separating the regions of curling up and curling down. The difference in the vertical displacements at the center and comer decreased as the stiffness of the underlying layer became larger, and the upper layer's material of the underlying layers affected the curling behavior of the slab.

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Optimum Slab-Lifting Positions for Precast Concrete Pavement Construction (프리캐스트 콘크리트 포장 시공 시 최적 슬래브 리프팅 위치)

  • Kim, Seong-Min;Cho, Byoung-Hooi;Han, Seung-Hwan
    • International Journal of Highway Engineering
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    • v.9 no.2 s.32
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    • pp.27-37
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    • 2007
  • This research was conducted to determine the optimum lifting positions on precast concrete slabs for precast concrete pavement construction, based on the analysis of concrete stress distribution under various lifting conditions. To analyze stresses in concrete slabs, the finite element method was implemented and a numerical model of the precast slab that was going to be used in the experimental construction was developed. Changes in the stress distribution due to the lifting angle were investigated because slab lifting is not always performed in the perpendicular direction to the slab surface. In addition, the effect of the lifting level, the distance between the neutral axis of the slab and the lifting point, on the stress distribution was investigated since the lifting point is not always at the neutral axis of the slab. To consider the actual steel design of the precast slab, the effect of the reinforcement near the lifting point was also investigated. From this study, the optimum lifting positions of the precast slabs were determined according to the lifting angle and level, and the results were compared with the lifting positions used in the PCI standards.

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Flexural & Fatigue Evaluation of Link Slab for Continuous Girder-Type Precast Modular Bridges (거더형식 프리캐스트 모듈러교량 연속화 지점부에 적용되는 연결슬래브의 휨성능 및 피로성능 평가)

  • Joo, Bong-Chul;Song, Jae-Joon;Lee, Sang-Yoon
    • Journal of the Korea Concrete Institute
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    • v.25 no.5
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    • pp.517-528
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    • 2013
  • The modular technology has been already applied in automotive industry, plant and shipbuilding industry. Recently, the modular technology was applied in bridge construction. The modular bridge is different from the existing precast bridges in terms of standardized design that the detailed design of members is omitted by using the standard modules; the design of the modular bridge is completed by only assembling the standard modules without design in member level. The girder-type precast modular bridge has been developed as a simply supported bridge. The girder-type precast modular bridge could be applied to the multi-span bridges through the continuity method. The continuity of the girder-type precast modular bridge is achieved by using the link slab which is easy to construction and appropriate to the rapid construction. The link slabs have been used as the type of reinforced concrete structure in US from the 1950's. In 2000's, the link slab using the engineered cementitious concrete (ECC link slab) has been developed. In this study, the RC type link slab which is more reproducible and economic relative to the ECC link slab was used for the continuity of the girder-type precast modular bridges, and the construction detail of RC type link slab was modified. In addition, the modified iterative design method of RC type link slab was proposed in this study. To verify the proposed design method, the flexural tests were conducted using the RC type link slab specimens. Also, the fatigue test using the mock-up specimen was conducted with cyclic loading condition up to two million cycles.