• Title/Summary/Keyword: 3점 휨 실험

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Experiment of Flexural Behavior of Composite Beam with Steel Fiber Reinforced Ultra High Performance Concrete Deck and Inverted-T Steel Girder (강섬유로 보강된 초고성능 콘크리트 바닥판과 역T형 강거더 합성보의 휨거동 실험)

  • Yoo, Sung-Won;Ahn, Young-Sun;Cha, Yeong-Dal;Joh, Chang-Bin
    • Journal of the Korea Concrete Institute
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    • v.26 no.6
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    • pp.761-769
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    • 2014
  • Ultra high performance concrete (UHPC) has been developed to overcome the low strengths and brittleness of conventional concrete. Considering that UHPC, owing to its composition and the use of steel fibers, develops a compressive strength of 180 MPa as well as high stiffness, the top flange of the steel girder may be superfluous in the composite beam combining a slab made of UHPC and the steel girder. In such composite beam, the steel girder takes the form of an inverted-T shaped structure without top flange in which the studs needed for the composition of the steel girder with the UHPC slab are disposed in the web of the steel girder. This study investigates experimentally and analytically the flexural behavior of this new type of composite beam to propose details like stud spacing and slab thickness for further design recommendations. To that goal, eight composite beams with varying stud spacing and slab thickness were fabricated and tested. The test results indicated that stud spacing running from 100 mm to 2 to 3 times the slab thickness can be recommended. In view of the relative characteristic slip limit of Eurocode-4, the results showed that the composite beam developed ductile behavior. Moreover, except for the members with thin slab and large stud spacing, most of the specimens exhibited results different to those predicted by AASHTO LRFD and Eurocode-4 because of the high performance developed by UHPC.

Experimental Study on Fracture Behavior of Low-Heat Concrete, by Three-Point Bent Test (3점 휨시험에의한 저발열콘크리트의 파괴거동에 곤한 실험적 연구)

  • 조병완;박승국
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.04a
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    • pp.199-204
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    • 1998
  • To analysis the failure character of Low-Heat concrete which is used to prevent the thermal crack caused by hydration heat, static loading test was performed by this test method, "Determination of the Fracture Energy of Motar and Concrete by Means of Three-Point Band Tests on Notched Beam" (suggested by RILEM 50-FMC Committe). This study compared and analysised the fracture energy of Mode I (opening mode), the most general pattern in the view of water-cemente ratio(W/C), compressive strength and age of Ordinary Portland Concrete and Low-Heat Concrete under the same mixture. The test results show that the case of Ordinary Portland Concrete and Low-Heat Concrete, low Water-Cemente ratio(W/C) cause the increase of fracture energy, and high failure-strength decrease failure-deflection, and the fracture energy of Low-Heat Concrete is similar to Ordinary Portland Concrete as the age increase. increase.

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Analysis of Stress Behavior on Field Welded Joints of U-rib in Steel Bridge (U리브 현장용접이음부 응력거동에 관한 연구)

  • Kang, Chang Ib;Choi, Seong Min;Kook, Seung Kyu;Lee, Dong Uk
    • Journal of Korean Society of Steel Construction
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    • v.16 no.3 s.70
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    • pp.387-396
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    • 2004
  • In this paper, stress analysis anda 3-point bending fatigue test were conducted on the full-scale specimen to investigate the effects of misalignment at the U-rib welded joint due to misfitting in the steel deck bridge. In addition, the researchers investigated the direction and starting point of fatigue cracks by SEM (Scanning Electron Microscope) and beach mark. The results of the stress analysis show that maximum stress occurred at the bottom corner of the U-rib, and that the stress was large when the magnitude of the misalignment was large. On the other hand, the results of the static loading test of the full-scale specimen show that stress was large at the bottom corner of the U-rib. In addition, fatigue life was short when the misalignment was large and fatigue life was short when the misalignment was large and fatigue life was short when the misalignment was large and fatigue life was large when the misalignment was small, as indicated by the results of both the static loading test and the fatigue test. From the observation of the failure surface, fatigue cracks began manifesting at the root of the base metal and proceeded to the bead surface (weld toe).

Evaluation of the Bending Behavior of RC beam by Using Color-based Image Processing Method (색상에 기반한 영상분석기법을 이용한 콘크리트 거더의 휨 거동 분석)

  • Woo, Tae-Ryeon;Jung, Chi-Young;Kim, In-Tae;Lee, Jong-Han;Cheung, Jin-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.4
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    • pp.48-54
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    • 2020
  • Cracks in reinforced concrete structures are the most common type of damage and are used as important analytical data to understand the fracture behavior characteristics of structures. Currently, there is a problem that most of the crack investigation relies on visual inspection, therefore many researchers have proposed image analysis techniques to improve the problem. In this study, we proposed a crack evaluation method to be applied at an indoor experimental level using image analysis method. The image analysis technique using color is for distinguishing a boundary surface between objects existing in an image, and is a method for separating similar colors into one region based on a predefined color. In this study, to improve the accuracy of image analysis, blue paint was applied to the concrete surface and bending experiments were performed. The image analysis method was able to measure the crack width with superior accuracy compared to the crack diameter, and at the same time, it was also possible to analyze the deflection of the beam. Both the crack and deformation were able to confirm the accuracy similar to the existing measurement method, and it was found that the image analysis method was very excellent in terms of applicability.

Effect of Long-Term Load on Flexural Crack Widths in FRP-Reinforced Concrete Beams (장기하중이 FRP-보강근 콘크리트 보의 휨균열폭에 미치는 영향)

  • Choi, Bong-Seob
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.12
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    • pp.694-701
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    • 2018
  • Larger crack widths can be observed more in FRP-reinforced concrete members than in steel-reinforced concrete members as a result of the lower elastic modulus and bond strength of FRP reinforcement. The ACI 440.1R-15 design guide provides equations derived as the maximum bar spacing to control the crack widths indirectly. On the other hand, it is not concerned with long-term effects on the crack control design provisions. This study provides suggestions for how to incorporate time-dependent effects into the crack width equation. The work presented herein includes the results from 8 beams composed of four rectangular and T-shaped FRP-reinforced concrete beams tested for one year under four-point bending. Over a one year period, the crack widths increased as much as 2.6~3.0 times in GFRP and AFRP-reinforced specimens and 1.1~1.4 times in the CFRP-reinforced specimens compared to steel-reinforced specimens. In addition, the average multiple for crack width at one year relative to the instantaneous crack width upon the application of the sustained load was 2.4 in the specimens with a rectangular section and 3.1 in the specimens with a T-shaped section. As a result, it is recommended conservatively that the time-dependent coefficient be taken as 2.5 for the rectangular beams and 3.5 for T-beams.

Shear Strength Model for Interior Flat Plate-Column Connections (무량판 슬래브-기둥 내부 접합부에 대한 전단강도모델)

  • Choi, Kyoung-Kyu;Park, Hong-Gun
    • Journal of the Korea Concrete Institute
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    • v.22 no.3
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    • pp.345-356
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    • 2010
  • An alternative design method for interior flat plate-column connections subjected to punching shear and unbalanced moment was developed. Since the slab-column connections are severely damaged by flexural cracking before punching shear failure, punching shear was assumed to be resisted mainly by the compression zone of the slab critical section. Considering the interaction with the flexural moment of the slab, the punching shear strength of the compression zone was evaluated based on the material failure criteria of concrete subjected to multiple stresses. The punching shear strength was also used to evaluate the unbalanced moment capacity of the slab-column connections. For verification, the proposed strength model was applied to existing test specimens subjected to direct punching shear or combined punching shear and unbalanced moment. The results showed that the proposed method predicted the strengths of the test specimens better than current design methods in ACI 318 and Eurocode 2.

Simulation of Multi-Cracking in a Reinforced Concrete Beam by Extended Finite Element Method (확장유한요소법을 이용한 철근 콘크리트 보의 다중균열 해석)

  • Yoo, Hyun-Suk;Kim, Han-Soo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.29 no.2
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    • pp.201-208
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    • 2016
  • Recently, extensive research on crack analysis using extended finite element method(XFEM) which has main advantages in element re-meshing and visualization of cracks has been conducted. However, its application was restricted to the members of a single material. In this study, the applicability and feasibility of the XFEM to the multiple crack analysis of reinforced concrete beams were demonstrated. ABAQUS which has implemented XFEM was used for the crack analysis and its results were compared with test results. Enriched degree-of-freedom locking phenomenon was discovered and its causes and the ways to prevent it were suggested. The locking occurs when cracks in the adjacent elements simultaneously develop. A modelling technique for multiple cracking similar to test results was also proposed. The analysis with XFEM showed similar results to the tests in terms of crack patterns, spacing of cracks, and load-deflection relationship.

A Study on the Flexural Fatigue Behavior of R/C Beams Repaired with Concrete-Polymer Composites (유기 및 유기재료로 보수된 R/C 보의 휨 피로거동에 관한 연구)

  • 심종성;황의승;배인환;이은호
    • Magazine of the Korea Concrete Institute
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    • v.7 no.6
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    • pp.233-241
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    • 1995
  • In this thesis, the fatigue tests were performed on a series of R /C beams repaired with co& crete-lmlyrner composites to investigate the fatigue bahavior. The three point loading system is used in the fatigue tests. In these tests, relations between the repeated loading cycles and mid-span deflections, number of repeated loading cycles when repaired beams were fractured, the bonding performance of repair materials were observed. On this basis, the mid-span deflections, the crack growth and failure mode of repaired R /C beams were studied. A S-N curve was drawn to present the fatigue strength of repaired beams. From the test results, it was shown that behavior of R /C beams repaired with polymer-cement series were very sirnillar to control beam about bonding performance, mid-span deflections and fatigue strength according to S-N curve drawn by the regression anlysis on the fatigue test results.

The Properties of Durability and Strength of Fiber-Reinforced Polymer-Modified Mortars Using Eco-Friendly UM Resin (친환경 UM수지를 사용한 섬유보강 폴리머 시멘트 모르타르의 내구성 및 강도 특성)

  • Kwon, Min-Ho;Seo, Hyun-Su;Lim, Jeong-Hee;Kim, Jin-Sup
    • Journal of the Korea Concrete Institute
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    • v.25 no.3
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    • pp.313-320
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    • 2013
  • In this study, performance of fiber-reinforced polymer-modified mortar was studied for the development of eco-friendly materials for high performance repair and reinforcement. The general cement mortar and eco-friendly UM resin was mixed with a certain percentage for increased durability. To increase the strength of the polymer-modified mortar, PVA fiber, steel fiber and hybrid fiber were added at a constant rate. Hybrid fiber is contains the same percentage of PVA fiber and steel fiber. In order to determine the strength properties of fiber-reinforced polymer-modified mortar, the compressive strength test, the splitting tensile strength test and the flexural strength test were performed. And, in order to determine the durability properties of fiber-reinforced polymer-modified mortar, water absorption test and chemical resistance test were performed. From the experimental results, polymer-modified mortar using UM resin was improved durability. And the tensile strength and flexural strength increased, which were the vulnerability of fiber reinforced polymer-modified mortar. From this study, fiber-reinforced polymer-modified mortar using eco-friendly UM resin can be used to repair and reinforcement for the external exposure of concrete structures to improve the durability.

Strut-Tie Models and Load Distribution Ratios for Reinforced Concrete Beams with Shear Span-to-Effective Depth Ratio of Less than 3 (I) Models and Load Distribution Ratios (전단경간비가 3 이하인 철근콘크리트 보의 스트럿-타이 모델 및 하중분배율(I) 모델 및 하중분배율)

  • Chae, Hyun-Soo;Yun, Young Mook
    • Journal of the Korea Concrete Institute
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    • v.28 no.3
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    • pp.257-265
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    • 2016
  • The failure behavior of reinforced concrete beams is governed by the mechanical relationships between the shear span-to-effective depth ratio, flexural reinforcement ratio, load and support conditions, and material properties. In this study, two simple indeterminate strut-tie models which can reflect all characteristics of the failure behavior of reinforced concrete beams were proposed. The proposed models are effective for the beams with shear span-to-effective depth ratio of less than 3. For each model, a load distribution ratio, defined as the fraction of load transferred by a truss mechanism, is also proposed to help structural designers perform the rational design of the beams by using the strut-tie model approaches of current design codes. In the determination of the load distribution ratios, the effect of the primary design variables including shear span-to-effective depth ratio, flexural reinforcement ratio, and compressive strength of concrete was reflected through numerous material nonlinear analysis of the proposed indeterminate strut-tie models. In the companion paper, the validity of the proposed models and load distribution ratios was examined by applying them to the evaluation of the failure strength of 335 reinforced concrete beams tested to failure by others.