• Title/Summary/Keyword: 인장철근

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Evaluation of Shear Strength of Precast-prestressed Hollow Core Slabs Based on Experiments (실험을 통한 프리캐스트-프리스트레스트 중공슬래브의 전단강도)

  • Han, Sang-Whan;Moon, Ki-Hoon;Kang, Dong-Hoon;Im, Ju-Hyeuk;Kim, Young Nam
    • Journal of the Korea Concrete Institute
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    • v.26 no.5
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    • pp.635-642
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    • 2014
  • The weight of concrete could be reduced by using hollow core slabs instead of heavy solid slabs, leading to cost reduction. The long span be also achieved by introducing prestress in hollow core slabs. but the evaluation of shear strength of precast-prestressed hollow core slabs are needed because the cross section is reduced in web and arranging shear reinforcement is not possible. In this study, the shear strength of precast-prestressed hollow core slabs were evaluated based on experimental tests. For this purpose, six full scale specimens were made and tested. The shear strength of the specimens were compared with those evaluated from current design provision(EC2 ACI, EN1168 and AASHTO).

A Study of the Advanced Composite Material Slab for Light Weight of Tall Building (초고층빌딩 경량화를 위한 복합신소재 슬래브에 관한 연구)

  • Han, Bong-Koo
    • Composites Research
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    • v.27 no.1
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    • pp.7-13
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    • 2014
  • For each construction material used, there is certain theoretical limit in sizes. For tall building construction, the reduction in slab weight is the first step to take in order to break such size limits. In this paper, the feasibility of such objective is proven and given by numerical analysis result. For a typical building slab, both concrete and advanced composite sandwich panels are considered. The concrete slab is treated as a special orthotropic plate to obtain more accurate result. For each panel, the deflection under the dead and live loads is compared, since both tensile and compressive strengths of the composites are far more higher than those of concrete. All types of sandwich panels considered, except one case, have self-weights less than one tenth of that of the reinforced concrete slab, with deflections less than that of the reinforced concrete slab.

Moment Magnifier Method for RC Flat Plate Subject to Combined Axial Compressive and Floor Load (면내 압축력을 받는 플랫 플레이트 슬래브에 대한 모멘트 증대법)

  • Park, Hong-Gun
    • Magazine of the Korea Concrete Institute
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    • v.11 no.1
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    • pp.243-254
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    • 1999
  • This paper presents a numerical study for developing the moment magnifier method that is applicable to RC flat plates subject to combined axial compressive and floor load. For the nonlinear finite element analysis, a computer program addressing material and geometric nonlinearities was developed. The flat plates to be studied are designed in accordance with the Direct Design Method in Korean Building Code for Structural Concrete. This paper proposes the buckling force and the moment magnification factor for the flat plate under the governing load condition that is the combined vertical and subsequently applied uniaxial compressive load. The buckling force is defined with two ingredients: the buckling coefficient and the effective flexural rigidity. Parametric studies are performed to investigate variations of the buckling coefficient and the effective flexural rigidity. Based on the numerical results, this paper provides the design values of the buckling coefficient and the effective flexural rigidity, and the design procedure for the moment magnifier method.

Shear and Bond Strength of Activated Hwangtoh Concrete Beam (활성 황토 콘크리트 보의 전단 및 부착 강도)

  • Lee, Nam-Kon;Park, Hong-Gun;Hwang, Hye-Zoo
    • Journal of the Korea Concrete Institute
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    • v.22 no.5
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    • pp.685-694
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    • 2010
  • As a eco-friendly material, Hwangtoh (red clay) has been studied for complete or partial replacement of portland cement. Most of existing studies focused on the material properties of the Hwangtoh concrete including the compressive strength, drying shringkage, and creep. In the present study, the shear strength of the beams made with the Hwangtoh concrete was tested. Further, bond strength of tension re-bars embedded in the Hwangtoh concrete was tested. One of the concrete tested consisted of activated Hwangtoh replacing 20% of the cement. The other consisted 100% activated. Hwangtoh replacing all the cement. The beam specimens were tested under two point static loading. The test result showed that the shear strength of activated Hwangtoh concrete beams replacing 20% and 100% of cement was equivalent to that of the ordinary portland cement concrete beam. However, the bond strength of activated Hwangtoh concrete replacing 100% of the cement was less than that of the ordinary portland cement concrete.

Strength of Reinforced Concrete Members in Pure Torsion (순수(純粹)비틀림을 받는 철근(鐵筋)콘크리트 부재(部材)의 내력(耐力))

  • Shin, Hyun Mook;Kim, Eun Kyun;Kim, Seon Il
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.8 no.2
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    • pp.125-133
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    • 1988
  • To establish the rational design method, it is very important that predict accurately load-deformation response on reinforced concrete members. Torque-twist curves of reinforced concrete members in pure torsion were proposed recently by Collins and Hsu, etc. But, it is found that torsional strength of reinforced concrete members based on Hsu's theory is underestimated in the over-all load region except the ultimate state. In this paper, an attempt is made to present the higher-precision of torsional strength on arbitrary loading condition. For this purpose, constitutive equations are derived from which an estimate can be made of the torsional behavior of reinforced concrete members under the pure torsion. Tension stiffness of concrete in both the cracked and uncracked state have been considered. A softening effect that reduces the strength of the concrete by the diagonal cracking of concrete have been appropriately deliberated. Particularly, the experiments was done with 14 test beams to investigate the validity of theoretical analysis.

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A Numerical Study on the Behavior of Shotcrete Reinforced by Various Steel Supports (강재로 보강된 숏크리트 거동의 수치해석적 연구)

  • Lee, Sang-Don;Park, Yeon-Jun;Lim, Doo-Chul;Son, Jeong-Hun;You, Kwang-Ho;Kim, Su-Man
    • Tunnel and Underground Space
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    • v.18 no.3
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    • pp.226-238
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    • 2008
  • The steel ribs which are used to enhance the supporting capability of the shotcrete are estimated to be very effective, but their characteristics depending on the types of steel support are not well understood enough to be considered in the design stage. This paper describes the behavior of the shotcrete reinforced by various types of steel supports. Through flexural toughness test, major strength parameters such as flexural tensile strength, equivalent flexural tensile strength and residual tensile strength were obtained and used in the numerical analyses. Test results show that steel rebar was not as dependable as H-beam or lattice girder but close examination of the test results revealed that the specimen was failed in shear because of the shorter span than desired. Therefore tests on the properly dimensioned specimens are necessary for valid evaluation of the steel rebar reinforced shotcrete. In the first set of numerical stability analyses, shotcrete and steel supports were modelled separately. Then compared with the second set of analyses in which shotcrete and steel supports were regarded as a composite material. The two results coincided reasonably and this equivalent model turned out to be useful.

Microstructure and Tensile Properties of 700 MPa-Grade High-Strength and Seismic Resistant Reinforced Steel Bars (700 MPa급 고강도 및 내진 철근의 미세조직과 인장 특성)

  • Hong, Tae-Woon;Lee, Sang-In;Hwang, Byoungchul
    • Korean Journal of Materials Research
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    • v.28 no.7
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    • pp.391-397
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    • 2018
  • This study deals with the microstructure and tensile properties of 700 MPa-grade high-strength and seismic reinforced steel bars. The high-strength reinforced steel bars (600 D13, 600 D16 and 700 D13 specimens) are fabricated by a TempCore process, while the seismic reinforced steel bar (600S D16 specimen) is fabricated by air cooling after hot rolling. For specimens fabricated by the TempCore process, the 600 D13 and 600 D16 specimens have a microstructure of tempered martensite in the surface region and ferrite-pearlite in the center region, while the 700 D13 specimen has a microstructure of tempered martensite in the surface region and bainite in the center region. Therefore, their hardness is the highest in the surface region and shows a tendency to decrease from the surface region to the center region because tempered martensite has a higher hardness than ferrite-pearlite or bainite. However, the hardness of the 600S D16 specimen, which is composed of fully ferrite-pearlite, increases from the surface region to the center region because the pearlite volume fraction increases from the surface region to the center region. On the other hand, the tensile test results indicate that only the 700 D13 specimen with a higher carbon content exhibits continuous yielding behavior due to the formation of bainite in the center region. The 600S D16 specimen has the highest tensile-to-yield ratio because the presence of ferrite-pearlite and precipitates caused by vanadium addition largely enhances work hardening.

Improvement of Structural Performance of RC Beams retrofitted Hybrid Fiber using Recycled Coarse Aggregate and Ground Granulated Blast Furnace Slag (순환굵은골재 및 고로슬래그 미분말을 사용한 하이브리드섬유보강 철근콘크리트 보의 구조성능 개선)

  • Yi, Dong-Ryul;Ha, Gee-Joo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.6
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    • pp.1-10
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    • 2014
  • In this study, thirteen reinforced concrete beams, ground granulated blast furnace slag, replacing recycled coarse aggregate with PVA fiber (BSPG series) and recycled coarse aggregate with hybrid fiber ($BSPGR_1$, $BSPGR_2$ series), and standard specimen (BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to improve and evaluate the Structural performance of such test specimens, such as the load-displacement, the failure mode, and the maximum load carrying capacity. All the specimens were modeled in 1/2 scale-down size. Test results showed that test specimens ($BSPGR_1$, $BSPGR_2$ series) was increased the compressive strength by 13%, the maximum load carrying capacity by 4~21% and the ductility capacity by 4~28% in comparison with the standard specimen (BSS). And the specimens ($BSPGR_1$, $BSPGR_2$ series) showed enough ductile behavior and stable flexural failure.

Shear Behavior between Ground and Soil-Nailing (지반과 쏘일네일링 사이의 전단거동에 관한 연구)

  • Seo, Hyung-Joon;Lee, In-Mo
    • Journal of the Korean Geotechnical Society
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    • v.30 no.3
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    • pp.5-16
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    • 2014
  • Soil-nailing has two main resistance factors: skin friction between ground and grouting; and tension load of reinforced material. These two factors will affect the load-displacement curve when performing soil-nailing pullout tests. The purpose of this paper is to figure out the shear behavior between ground and soil-nailing focusing on the net load-displacement behavior during soil-nailing pullout tests. Firstly, the net load-displacement curve between ground and grouting is estimated theoretically. Then, in-situ pullout load tests are performed on various ground conditions to obtain the load-displacement curve occuring between ground and grouting. Since the measured shear displacement includes elongation of the reinforced material (steel nails), the net load-displacement curve can be obtained by subtracting the elongation magnitude of steels from the measured displacement. It was found that the measured net load-displacement curve matches reasonably well with the theoretically estimated curve.

Effect of Bond Action of Longitudinal Bars on Shear Transfer Mechanism in RC Beams (RC 보에서의 전단저항기구와 주철근의 부착 작용과의 관계)

  • Kim Kil-Hee
    • Journal of the Korea Concrete Institute
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    • v.17 no.4 s.88
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    • pp.513-520
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    • 2005
  • The uniform truss mechanism is widely accepted as a shear transfer mechanism in reinforced concrete members. However, the uniform truss action cannot be expected when the bond stress distribution is not constant along longitudinal bars. A test method in which only the truss action takes place is developed and conducted to investigate the truss actions under various bond contributions. Based on the experimental results and analysis, the following findings can be obtained: 1) The bond stress distribution depends on the axial compression force, the amount of shear reinforcement and loading conditions. 2) The analysis using the combined truss model consisting of uniform and fan-shape trusses can predict the experimental results