• Title/Summary/Keyword: 콘크리트 슬래브

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The Flexural Behavior including Ductility of Half Precast Concrete Slab with Welded Deformed Wire Fabric (용접철망을 사용한 반두께 P.C.슬래브의 휨 및 연성거동)

  • 이광수;최종수;조민형;신성우
    • Magazine of the Korea Concrete Institute
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    • v.6 no.4
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    • pp.153-160
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    • 1994
  • Ten Half precast concrete slabs reinforced with welded deformed wire fabric were tested under two concentrated loads to investigate the flexural moment and ductile capacity. The test variables were the compressive strength of topping concrete, quantitative roughness, and reinforcernent ratio. The effects of each test variables were studied separately. Test results were as followings. The ultimate strength design method is applicable to predict flexural strength for Half P.C. concrete slab with welded deformed wire fabric and quantitative roughness. It is proper to consider 0.0035 strain ;is yielding stress of the welded deformed wire fabric. The ductility index of Half precast concrete slab with welded deformed wire fabric showed lower value. Therefore to enhance the ductility capacity the normal defomed bar should be used with the welded deformed wire fabric for the longitudinal reinforcement.

Numerical Investigation on Cracking of Bridge Deck Slabs with Latex Modified Concrete Overlays (라텍스 개질 콘크리트 교량 교면 포장부 균열에 대한 수치해석 연구)

  • Choi, Kyoung-Kyu
    • Journal of the Korea Concrete Institute
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    • v.22 no.1
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    • pp.77-84
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    • 2010
  • Latex modified concrete (LMC) exhibits improved material properties including high tensile strength and durability compared with conventional concrete, and hence LMC has been used as protective layers over the bridge deck slabs to increase their service life with underlying assumption of excellent bond behavior between the LMC overlay and the concrete substrate. In this study, the effect of the primary parameters of the concrete substrate (i.e., shrinkage, stiffness and cracking capacity) as well as the LMC overlay thickness on the probability of cracking of the bridge deck slabs using LMC overlays was investigated by carrying out the finite element analysis that simulated the bond behavior of LMC overlays on normal strength concrete (NSC) and HPC bridge deck slabs. Based on the results of the numerical analysis, it is concluded that the relatively high shrinkage strains and stiffness of HPC slabs can increase its probability of cracking in bridge deck slabs using LMC overlay.

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.

Improved Transmission of UHSC Column Loads by Puddling of Fiber Reinforced UHSC (강섬유 보강 초고강도 콘크리트의 확대 타설을 통한 기둥 하중 전달 성능 향상)

  • Lee, Joo-Ha;Yang, Jun-Mo;Lee, Seung-Hoon;Yoon, Young-Soo
    • Journal of the Korea Concrete Institute
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    • v.19 no.2
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    • pp.209-216
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    • 2007
  • This study reports on the structural characteristics of slab-column connections using fiber-reinforced ultra-high-strength concrete (UHSC). Compression tests were performed on two slab-column and four isolated column specimens. In the column load tests, slab loads were also applied on the slab-column specimens so that the actual confinement condition at the slab-column joint was considered. The main parameter investigated was the "puddling" of fiber-reinforced UHSC. This paper also investigates the effects of some parameters, such as confinement of slab concrete, steel fibers, and concrete strength of the joint, related to the ability of the slab-column specimens and isolated column specimens without the surrounding slab to transmit axial loads from the UHSC columns through slab-column connections. Furthermore, the ACI Code (2005) and the CSA Standard (2004) are compared to the experimental results. The beneficial effects of the puddling of fiber-reinforced UHSC on the transmission of column loads through slab-column connections are demonstrated.

Jacking Force and Camber for Precast Concrete Slab Reinforcing (프리캐스트 콘크리트 슬래브 보강을 위한 잭킹력과 솟음)

  • Lho, Byeong-Cheol
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.25 no.2
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    • pp.43-48
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    • 2021
  • Precast concrete can be used to reduce construction period and enhance construct ability. However structural problems could be occurred due to the wrong application of boundary condition and misunderstanding of structural behavior in the process of segmentation of original structure system. I experienced a serious deflections and cracks due to the increase of bending moment and creep after the construction of precast concrete slab, and we learned that this is from the misunderstanding of support conditions and structure behaviors of precast slab panel. Two support columns under the precast slab are inserted to reduce the bending moment, and the camber according to jacking force should be estimated for the structural safety during the reinforcing work. A proper support condition and the flexural stiffness of precast concrete slab were applied to check the deflection and crack for existing structure by inverse analysis, and we can estimate the camber according to jacking force of the precast concrete slab, and suggest a method to make safe structure.

Effect of temperature and moisture on curling of early age concrete slabs (재령 초기 콘크리트 슬래브의 컬링에 미치는 온도와 수분의 영향)

  • Sun, Ren-Juan;Nam, Young-Kug;Hong, Seung-Ho;Jeong, Jin-Hoon
    • International Journal of Highway Engineering
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    • v.10 no.1
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    • pp.105-115
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    • 2008
  • It is known that the long-term behavior and performance of jointed concrete pavement due to slab curling are affected by the environmental factors such as temperature, moisture, and so on. However, any relationships between the curling and its factors have not been defined clearly yet because of insufficient detailed investigation. The temperature, relative humidity, strain, vertical displacement of a concrete slab, and horizontal movement of its transverse joints were investigated by various sensors and devices instrumented in the slab of a concrete pavement section constructed for this study. The constraint of the curling by joint stiffness was investigated in addition to effect of the temperature and moisture on the early aged concrete slab by analyzing the field data measured for approximately 4days from concrete placement. The curling of the concrete slab showed 24hour cycles mainly because of the temperature effect, and the upward curling gradually increased because of the long-term effect of drying shrinkage of the concrete. The magnitude and variation of the curling were significantly affected by the joint stiffness which is comprised of aggregate interlocking and other factors. The effect of the variation of the seasonal joint stiffness varying with the temperature and long-term drying shrinkage on the slab curling will be investigated as a further study.

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An Experimental Study on the Structural Bechavior of Two-layered Reinforced Concrete Slabs in Bridges (교량에서 2층 분리타설한 철근콘크리트 슬래브의 구조거동에 관한 실험연구)

  • 오병환;이형준;이명규;한승환
    • Magazine of the Korea Concrete Institute
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    • v.6 no.3
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    • pp.162-172
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    • 1994
  • The flexural and horizontal shear behavior of overlaid concrete slabs with polymer interface is investigated in the present study. An experimental program was set up and several series of overlaid concrete slabs have been tested to study the effect of different surface preparations and dowel bars between old slab and overlay under service and ultimate loads. 'The cracking and ulti mate load behavior for various cases including acryl emulsion treatment and doweled joints has been studied. The present study indica.tes that the overlaid concrete slabs behave integrally with existing bottom slabs up to ultimate range for rough and doweled joints with polymer interface. The pres ent study provides a firm base for the realistic design of two-layered RC slabs in bridges.

Flexural Behaviors of High Performance Hollow Core Slabs with Upper Strands (상부강선을 갖는 고성능 중공슬래브의 휨거동)

  • 김인규;박현석;유승룡
    • Journal of the Korea Concrete Institute
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    • v.14 no.2
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    • pp.156-163
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    • 2002
  • Hollow core slabs generally have not been used for a bridge or a parking slab in Korea. In this study, high performance hollow core slabs, which have been the most thick one in domestic are re-designed and examined for practical use. Flexural tests were performed on four 315mm deep hollow core slabs to investigate adaptability for high vehicle live loadings and composite action with topping concrete. The precast slabs were pre-tensioned with ten strands of 1/2 inch diameter at the lower of slab and four strands of 1/2 inch diameter at the upper of slab, and cast with 80 mm deep topping concrete. Tested hollow core slabs showed ductile failure behaviors which were conformed to the current Ultimate Strength Design Method for a span of 10m up to the live load of 1,000 kgf/㎡. The rectangular md round shear cotters which were used for the composite action between precast and topping concrete, developed sufficient strengths because cracking, even micro had not been developed at the end of slabs up to the pure flexural tensile failure.

A Preliminary Study on Reduction of Shrinkage Stress in Concrete Slabs (콘크리트 슬래브 건조수축 응력 감소에 관한 초기연구)

  • Park, Jeong-Woo;Jeong, Young-Do;Lim, Jin-Sun;Jeong, Jin-Hoon
    • International Journal of Highway Engineering
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    • v.11 no.4
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    • pp.87-94
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    • 2009
  • Volume of concrete slab changes by variations of temperature and moisture after its placement. Shrinkage due to evaporation causes tensile stress in the slab when contraction of the slab is restrained by its self weight, friction with subbase, and etc. Actual tensile stress caused by the shrinkage was less than theoretically predicted stress according to previous studies. It was the stress reduction due to visco-elastic property of the early-age concrete slab partially restrained. In this study, strains of restrained circumferential, unrestrained circumferential, and unrestrained square pillar concrete specimens were measured to investigate stress reduction of the specimens with age of concrete. Elastic modulus of the concrete was measured at the age of 1, 3, 7, 14, 28 days and penetration test was performed. The stress reduction was calculated by input the test results into theoretical equations suggested by previous researchers. The stress reduction of the restrained concrete specimens will be applied to design of concrete pavements based on results of the study.

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Study on Stress Variation in Slab and Support of Shearwall-Type RC Apartment during Construction (전단벽식 아파트에서 시공중 슬래브 및 동바리의 응력변화에 대한 연구)

  • Kim Young-Chan
    • Journal of the Korean Society of Safety
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    • v.19 no.4 s.68
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    • pp.161-165
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    • 2004
  • Safety and efficiency in the construction of RC structures mainly depends on optimal operation of shore-slat systems. The disasters in RC construction are mainly due to excessive load applied to falsework and premature removal of supports. Development of sufficient compressive strength of early-age connote is essential for the safety of structures during construction. Most of studies on shore-slab interaction have focused on flat slab structures. In this study, load distributions in floor slabs and supports during the construction of shear wall-type RC apartment building structures is investigated using finite element analysis.