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  • Title/Summary/Keyword: shear strength of concrete

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Evaluation of Structural Behaviour of a Composite CFT Truss Girder Bridge (CFT 트러스 거더 합성형교의 구조거동 평가)

  • Chung, Chul-Hun;Kim, Hye-Ji;Song, Na-Young;Ma, Hyang-Wook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.30 no.2A
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    • pp.149-159
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    • 2010
  • This paper presents an experimental study on the structural behavior of composite CFT truss girder bridge with full depth precast panels. The length of span is 20,000 mm. The CFT truss girder is a tubular truss composed of chord members made of concrete-filled and hollow circular tubes. To determine fundamental structural characteristics such as the strength and deformation properties of composite CFT truss girder bridge, static and dynamic tests were conducted. The natural frequencies calculated by the FEM are in good agreement with experimental results obtained from dynamic test. Bracing have only a small effect on the natural frequencies of composite CFT truss girder bridge as indicated by the FEM results. The yield strength and deformation of the composite CFT truss girder bridges were investigated through a static bending test. Besides, the test results showed that uniform distribution of shear connectors can be applicable in composite CFT truss girder bridges.

An Experimental Study on Flexural Behavior of RC Beams Strengthened with Hi-Strength Bars(2) (고장력 인장봉으로 보강된 RC보의 휨거동에 관한 실험적 연구(2))

  • Shin, Kyung-Jae;Kwak, Myong-Keun;Bae, Kyu-Woong;Oh, Young-Suk;Moon, Jung-Ho
    • Journal of the Korea Concrete Institute
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    • v.18 no.5 s.95
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    • pp.603-610
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    • 2006
  • The external unbonded strengthening offers advantages in speed and simplicity of installation over other strengthening techniques. Unlike externally bonded steel plate or carbon fiber sheet, surface preparation of the concrete for installation of high-tension bar is not required and installation is not affected by environmental conditions. Anchoring pin or anchoring plate are installed at the end of beam to connect the high-tension bar to concrete beam. The deviator are used in order that supplementary external bars would follow the curvature of the tested beam. A set often laboratory tests on reinforced concrete beam strengthened using the technique are reported. The main test parameters are the section area of strengthening bar, the depth of deviator and the number of deviators. The paper provides a general description of structural behavior of beams strengthened using the technique. The test result of strengthened beam are compared with those from a reference specimen. It is shown that the reinforcing technique can provide greater strength enhancements to unstrengthened beam and that the provision of deviator enhances efficiency. The ultimate moment of specimen with two deviators was higher than that of specimens with one deviator. It is also shown that the external bars enhance strength of beams in shear.

Design Considerations and Pull-Out Behavior of Mechanical Anchor of Reinforcement (철근 기계적 정착장치의 설계 고려사항과 인발특성)

  • 천성철;김대영
    • Journal of the Korea Concrete Institute
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    • v.13 no.6
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    • pp.593-601
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    • 2001
  • In RC structure, sufficient anchorage of reinforcement is necessary for the member to produce the full strength. Generally, conventional standard hook is used for the reinforcement's anchorage. However, the use of standard hook results in steel congestion, making fabrication and construction difficult. Mechanical anchor offers a potential solution to these problems and may also ease fabrication, construction and concrete placement. In this paper, the required characteristics and the design considerations of mechanical anchor were studied. Also, the mechanical anchor was designed according to the requirements. To investigate the pull-out behavior and properness of mechanical anchorage, pull-out tests were performed. The parameters of tests were embedment length, diameter of reinforcement, concrete compressive strength, and spacing of reinforcements. The strengths of mechanical anchor were consistent with the predictions by CCD method. The slip between mechanical anchor and concrete could be controlled under 0.2mm. Therefore, the mechanical anchor with adequate embedment could be used for reinforcement's anchorage. However, it was observed that the strength of mechanical anchors with short spacing of reinforcements was greatly reduced. To apply the mechanical anchor in practice (e.g. anchorage of the beams reinforcements in beam-column joint), other effects that affect the mechanical anchor mechanism, such as confinement effect of adjacent member from frame action or effects of shear reinforcement, should be considered.

Effect of Crack Control Strips at Opening Corners on the Strength and Crack Propagation of Downsized Reinforced Concrete Walls (축소 철근콘크리트 벽체의 내력과 균열진전에 대한 개구부모서리 균열제어 띠의 영향)

  • Wang Hye-Rin;Yang Keun-Hyeok
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.4
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    • pp.40-47
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    • 2022
  • The present study aimed to examine the effectiveness of different techniques for controlling the diagonal cracks at the corners of openings on the strength, deformation, and crack propagation in reinforced concrete walls. The crack control strip proposed in this study, the conventional diagonal steel reinforcing bars, and stress-dispersion curved plates were investigated for controlling the diagonal cracks at the opening corners. An additional crack self-healing function was also considered for the crack control strip. To evaluate the volume change ratio and crack width propagation around the opening, downsized wall specimens with a opening were tested under the diagonal shear force at the opening corner. Test result showed that the proposed crack control strip was more effective in reducing the volume change and controlling the crack width around the opening when compared to the conventional previous methods. The crack control strip with crack healing feature displayed the superior performance in improving the strength of the wall and reducing the crack width while healing cracks occurred in the previous tests.

An Experimental Study on Seismic Performance of Two-story Reinforced Concrete Frames Retrofitted with Internal Steel Frame and Wall Type Friction Damper (내부 철골끼움골조 및 벽체형 마찰댐퍼(WFD)로 보강된 2층 철근콘크리트골조 내진성능에 대한 실험적 연구)

  • Yoo, Chang-Gi;Choi, Chang-Sik
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.6
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    • pp.64-72
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    • 2022
  • In this study, in order to confirm the seismic performance of reinforced concrete frames retrofitted with Wall Friction Damper(WFD), the test was conducted by setting two-story Reinforced concrete frames (reference specimen, OMF-N and specimen retrofitted with internal H-shaped steel frame and WFD, OMF-ALL(H)) as main variables. The WFD Seismic Retrofit Method is a mixture of strength improvement and energy dissipation methods. To prevent the pre-destruction of existing structure by friction force before sufficient energy dissipation of WFD, the internal H-shaped steel frame and chemical anchor that penetrates the side of the beam were used to install WFD. According to the test results, the OMF-N specimen showed an brittle failure pattern caused by the shear force of the R/C column after the maximum strength was expressed. The OMF-ALL(H) specimen showed that the reduction of pinching effect and the failure of the RC column occurred. Also, the maximum strength, cumulative energy dissipation and ductility of OMF-ALL(H) increased 3.01 times, 7.2 times and 1.72 times for OMF-N. As a results, test results revealed that the WFD Seismic Retrofit Method installed on Reinforced concrete structure improves the seismic performance and the strengthening effect is valid.

Seismic Evaluation of Beam-Column Joint Specimens of RC Special Moment Frames (철근콘크리트 특수모멘트골조의 보-기둥 접합부 실험체의 내진성능평가)

  • Lee, Ki-Hak;Seok, Keun-Yung;Jung, Chan-Woo;Shin, Young-Shik;Kang, Joo-Won
    • Journal of Korean Association for Spatial Structures
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    • v.8 no.2
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    • pp.85-93
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    • 2008
  • This study summarizes the results of a research project aimed at investigating the inelastic rotation capacity of beam-column joints of reinforced concrete special moment frames. All of the test specimens were classified as special moment frame (SMF), based on the design and detailing requirements of the ACI 318-02 provisions. The acceptance criteria, originally defined for steel moment frame connections in the 1997 edition of the AISC Seismic provisions, were used to evaluate the beam-column joints of the reinforced concrete moment frames. A total of 39 test specimens were examined in detail. Most of the joints that satisfy the design requirements for special moment frame structures were found to be ductile up to a plastic rotation of 3% without any major degradation in strength. This is mainly due to the stringent ACI 318-02 requirements for special moment frame joints. The presence of transverse beams increases confinement and shear resistance of joints, which results in better performance than for joints without transverse beams. All of the SMF connections that satisfy the ACI 318-02 limitations on joint shear stress turned out to meet the acceptance criteria.

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Experimental Analysis of Large Size Concrete-Filled Glass Fiber Reinforced Composite Piles Subjected to the Flexural Compression (대구경 콘크리트 충전 복합소재 파일의 휨-압축 거동에 대한 실험적 분석)

  • Lee, Sung Woo;Choi, Sokhwan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.5A
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    • pp.519-529
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    • 2009
  • Fiber reinforced composite materials have various advantages in mechanical and chemical aspects. Not only high fatigue and chemical resistance, but also high specific strength and stiffness are attained, and therefore, damping characteristics are beneficial to marine piles. Since piles used for marine structures are subjected to compression and bending as well, detailed research is necessary. Current study examine the mechanical behavior under flexural and/or compressive loads using concrete filled fiber reinforced plastic composite piles, which include large size diameter. 25 pile specimens which have various size of diameters and lengths were fabricated using hand lay-up or filament winding method to see the effect of fabrication method. The inner diameters of test specimens ranged from 165 mm to 600 mm, and the lengths of test specimens ranged from 1,350 mm to 8,000 mm. The strengths of the fill-in concrete were 27 and 40 MPa. Fiber volumes used in circumferential and axial directions are varied in order to see the difference. For some tubes, spiral inner grooves were fabricated to reduce shear deformation between concrete and tube. It was observed that the piles made using filament winding method showed higher flexural stiffness than those made using hand lay-up. The flexural stiffness of piles decreases from the early loading stage, and this phenomenon does not disappear even when the inner spiral grooves were introduced. It means that the relative shear deformation between the concrete and tube wasn't able to be removed.

Static Behavior of the Prestressed Concrete Deck Slab for Steel-Concrete Composite Two-Girder Bridges (강합성 2거더교 PSC 바닥판의 정적 거동)

  • 김영진;주봉철;이정우;김병석;박성용
    • Journal of the Korea Concrete Institute
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    • v.14 no.4
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    • pp.503-512
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    • 2002
  • Generally, the girder spacing of the two-girder composite bridge is from 5m up to 15m. To ensure the structural safety according to Korean Bridge Design Specification, the deck depth should be from 33 cm upto 73 cm. Using the transversal prestressing strands in concrete deck, we can reduce its depth about 10%. However, there is little experience on the design and construction of prestressed concrete(PSC) decks in Korea. This paper focuses on the behaviors of PSC deck. A literature survey is performed widely. Considering the characteristics of the two-girder bridge and the construction conditions in Korea, a cast-in-place PSC deck is recommended for the two-girder bridge with 6m girder spacing. To examine its structural behaviors and safety, three partial model deck specimens(3 m×5 m) with real scale are fabricated md tested. One(PS34-RS) is 34cm depth with the stiffness restraint in longitudinal edges for simulating the real bridge deck. Another(PS34-NS) is same depth without the stiffness restraint, and the other(PS28-NS) is 28cm depth with the stiffness restraint. Under the static patch loading, each specimen had a larger ultimate flexural strength than the design value. Specimens with the stiffness restraint (PS34-RS and PS28-RS) showed the punching shear failure mode and specimen without that(PS34-NS) showed the flexural failure mode.

Nonlinear Analysis of Shear Behavior on Pile-Sand Interface Using Ring Shear Tests (링전단시험을 이용한 말뚝 기초-사질지반 간 인터페이스 거동 분석)

  • Jeong, Sang-Seom;Jung, Hyung-Suh;Whittle, Andrew;Kim, Do-Hyun
    • Journal of the Korean Geotechnical Society
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    • v.37 no.5
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    • pp.5-17
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    • 2021
  • In this study, the shear behavior between pile-sandy soil interface was quantified based on series of rigorous ring shear test results. Ring shearing test was carried out to observe the shear behavior prior to failure and behavior at residual state between most commonly used pile materials - steel and concrete - and Jumunjin sand. The test was set to clarify the shear behavior under various confinement conditions and soil densities. The test results were converted in to representative friction angles for various test materials. Additional numerical analysis was executed to validate the accuracy of the test results. Based on the test results and the numerical validation, it was found that due to the dilative and contractive nature of sand, its interface behavior can be categorized in to two different types : soils with higher densities tend to show peak shear stress and moves on to residual state, while on the other hand, soils with lower densities tend to show bilinear load-transfer curves along the interface. However, the relative density and the confining stress was found to affect the friction angle only in the small train range, and converges as it progresses to large deformation. This study established a large deformation analysis method which can successfully simulate and predict the large deformation behavior such as ring shear tests. Moreover, the friction angle derived from the ring shear test result and verified by numerical analysis can be applied to numerical analysis and actual design of various pile foundations.

Seismic performance of RC columns retrofitted using high-strength steel strips under high axial compression ratios

  • Yang, Yong;Hao, Ning;Xue, Yicong;Feng, Shiqiang;Yu, Yunlong;Zhang, Shuchen
    • Structural Engineering and Mechanics
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    • v.84 no.3
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    • pp.345-360
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    • 2022
  • In this paper, the impact on seismic performance of an economical effective technique for retrofitting reinforced concrete (RC) columns using high-strength steel strips under high axial compression ratios was presented. The experimental program included a series of cyclic loading tests on one nonretrofitted control specimen and three retrofitted specimens. The effects of the axial compression ratio and spacing of the steel strips on the cyclic behavior of the specimens were studied. Based on the test results, the failure modes, hysteretic characteristics, strength and stiffness degradation, displacement ductility, and energy dissipation capacity of the specimens were analyzed in-depth. The analysis showed that the transverse confinement provided by the high-strength steel strips could effectively delay and restrain diagonal crack development and improve the failure mode, which was flexural-shear failure controlled by flexural failure with better ductility. The specimens retrofitted using high-strength steel strips showed more satisfactory seismic performance than the control specimen. The seismic performance and deformation capacity of the retrofitted RC columns increased with decreasing axial compression ratio and steel strip spacing. Based on the test results, a hysteretic model for RC columns that considers the transverse confinement of high-strength steel strips was then established. The hysteretic model showed good agreement with the experimental results, which verified the effectiveness of the proposed hysteretic model. Therefore, the aforementioned analysis can be used for the design of retrofitted RC columns.