• Title/Summary/Keyword: 횡구속압

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Stress-strain Model of Laterally Confined High-strength Concrete with the Compressive Fracture Energy (압축파괴에너지를 도입한 횡구속 고강도 콘크리트의 응력-변형률 모델)

  • Hong, Ki-Nam;Shim, Won-Bo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.1
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    • pp.54-62
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    • 2019
  • In this paper, a stress-strain model for high-strength confined concrete is proposed using compressive fracture energy. In the compression test performed by author in Reference [6], an acrylic bar with strain gauges was embedded in the center of the specimen to measure the local strain distribution. It was found from the test that the local strain measurement by this acrylic rod is very effective. The local fracture zone length was defined based on the local strain distribution measured by the acrylic rod. Specifically, it was defined as the length where the local strain increases more than twice of the strain corresponding to maximum stress. In addition, the stress-strain relationship of confined concrete with compressive fracture energy is proposed on the assumption that the amount of energy absorbed by the compressive members subjected to the given lateral confining pressure is constant regardless of the aspect ratio and size. The proposed model predicts even results from other researchers accurately.

Behavior of Circular Concrete Cylinders Confined with Both Steel Spirals and Fiber Composites (나선형 철근 및 섬유에 의하여 동시에 구속된 원형 콘크리트 실린더의 거동)

  • Lee Jung-Yoon;Oh Young-Jun;Jeong Hoon-Sik
    • Journal of the Korea Concrete Institute
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    • v.16 no.2 s.80
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    • pp.175-184
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    • 2004
  • When the columns of existing RC structures are repaired with FRP composites, the core concrete of the columns is confined by both materials of steel spirals (or steel hoops) and FRP composites because the FRP composites wrap the existing columns which have been already confined with steel spirals or hoops. As the stress-strain curves of steel and fiber are different to each other, the behavior of concrete columns confined with both steel spiral and FRP composites is also different to that of concrete columns confined with only steel spiral or FRP composites. Twenty four RC cylinders were tested in order to observe the behavior of RC cylinders confined with both materials. The observed results of the test showed that the behavior of the test cylinders confined with both materials was quite different to that of cylinders confined with only one material.

Prediction of the Maximum Strain of Circular Concrete Columns Confined with Fiber Composites (섬유에 의하여 구속된 원형 콘크리트 기둥의 최대변형률 예측)

  • Lee, Jung-Yoon;Jeong, Hoon-Sik
    • Journal of the Korea Concrete Institute
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    • v.15 no.5
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    • pp.726-736
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    • 2003
  • Concrete columns confined with high-strength fiber composites can enhance its strength as well as maximum strain. In recent years, several equations have been developed to predict the behavior of the concrete columns confined with fiber composites. While the developed equations can predict the compressive strength of the confined columns with reasonable agreement, these equations are not successful in predicting the observed maximum strain of the columns. In this paper, a total of 61 test results is analysed to propose an equation to predict both compressive strength and maximum strain of concrete cylinders. The proposed equation takes into account the effects of confining pressure and cylinder size. Furthermore, in order to verify the proposed stress-strain curve for concrete cylinders, six cylindrical specimens were tested. Comparisons between the observed and calculated stress-strain curves of the tested cylinders showed reasonable agreement.

Development of Design Method of Compression(SSC) Anchor (압축헝 앵커의 설계법 개발)

  • 임종철;홍석우;이태형;이외득
    • Journal of the Korean Geotechnical Society
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    • v.15 no.1
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    • pp.63-78
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    • 1999
  • For the design of compression anchor, three things should be considered. The first is a resistance force by skin friction, the second is a tension strength of tendon, and the third is a compressive strength of grout. Especially, compressive strength of grout is the most important design parameter of compression anchor. When compression anchor is pulled out from the ground, the compressive strength of grout increases by confining pressure of ground($\sigma_{tg$). Here, $\sigma_{tg$ is the confining pressure which is produced by earth pressure at rest and by lateral expansion of grout. We call this phenomenon of increase of confining pressure "poisson effect". In this paper, the design method of compression anchor called SSC anchor and the computer program for the design are developed through compression tests of anchor body grout.ody grout.

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An Experimental Study on Uniaxial Compressive Behavior of RC Circular Columns Laterally Confined with Prestressing Aramid Fiber Strap (아라미드 스트랩으로 프리스트레싱 횡구속된 RC 원형기둥의 일축압축거동에 관한 실험적 연구)

  • Han, Sang-Hoon;Hong, Ki-Nam;Lee, Jae-Bum
    • Journal of the Korea Concrete Institute
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    • v.21 no.2
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    • pp.159-168
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    • 2009
  • In this study, strength, stiffness and confinement effect with stress-strain and stress-volumetric strain curves for improved uniaxial compressive behavior of RC circular columns laterally confined with prestressing aramid fiber strap were experimentally investigated. The test variables were the specimens with or without axial reinforcing bar and the number and spacing of strap, prestressing level, the types of reinforcing fiber (CFS, GFS). As a result, the failure type of the columns was very stable and strength increase rate was about 73% comparison with the general RC columns. Moreover, the strain increase rate is very small and the axial displacement confinement effect was very effective compared with existry methods (CFS, GFS), the initial and final lateral confinement effect was excellent.

Experimental Study on the Triaxial Compressive Behaviour of Unsaturated Compacted Silt under Various Suction Levels (다양한 석션 레벨에서의 불포화실트의 삼축압축거동에 관한 실험적 연구)

  • Kim, Young-Seok;Oka, Fusao
    • Journal of the Korean Geotechnical Society
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    • v.24 no.1
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    • pp.25-35
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    • 2008
  • It has been recognized that the behaviour of unsaturated soil plays an important role in geomechanics. However, up to now, only a few experimental data are available for the technical difficulties related to both volume changes and suction measurements. In this study, the volume changes of unsaturated compacted silty soil were monitored with proximeter during various triaxial compression tests, which gave a realistic estimation in the volume changes of unsaturated soil sample. From the test results, the behaviours of wetting-induced collapses are observed during the drainage/water absorption tests. Under exhausted-drained conditions during shearing, the shear strength increases with an increasing initial suction. On the other hand, the volume changes become small with an increase in the initial suction. And, the volumetric strain during shearing is independent of the confining pressure.

A Numerical Study on Granular Compaction Pile Method Reinforcing by Using Lean-Mixed Concrete (빈배합 콘크리트로 보강된 조립토 다짐말뚝공법에 관한 기초연구)

  • Kim, Seung-Wook;Kim, Hong-Taek;Kim, Jeong-Ho;Baek, Seung-Cheol
    • Journal of the Korean GEO-environmental Society
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    • v.7 no.1
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    • pp.5-18
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    • 2006
  • Stone column or granular compaction pile have been used in widely during the several decades as a technique to reinforce soft cohesive soils and increase bearing capacity, accelerate consolidation settlement of the foundation soil. The bearing capacity of the granular compaction pile is governed mainly by the lateral confining pressure mobilized in the native soft soil to restrain bulging collapse of the granular pile. Therefore, the technique becomes unfeasible in soft, compressible clayey soils that do not provide sufficient lateral confinement. This paper presents the main results of numerical study of granular compaction pile which is partly mixed with lean concrete. 3D finite element analyses are performed with composite reinforced foundations by both granular compaction pile and partly mixed granular compaction pile with lean-mixed concrete. Finally, a regression formula for calculating settlement reduction coefficients is proposed in this study by using numerical analysis results and applicability of the proposed method is identified by a series of parametric study about settlement reduction coefficients.

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Bond Stress in Concrete Pilled Steel Tubular Column (CFT 기둥의 부착응력에 관한 연구)

  • 권승희;김진근
    • Journal of the Korea Concrete Institute
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    • v.13 no.2
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    • pp.93-98
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    • 2001
  • CFT column has excellent structural properties due to the composite action between concrete and steel tube. The bond behavior between the constituent elements has to be found for analyzing the behavior of CFT column. A new model is necessary because most of existing models for bond stress-slip relationship of the deformed bar cannot be applied to the CFT column. Therefore, the objective of this research is to develop a new model related to the bond behavior of CFT column considering the relation between bond stress and vertical stress, and the distribution of lateral stress under the confinement created by steel casing. From equilibrium condition, the formula for relationship between bond stress and vertical stress is derived, and the relationship for the lateral stresses of the CFT column section is obtained by an Airy stress function. The experiments are performed for five CFT column specimens axially loading on concrete alone. The relation between bond strength and lateral stress is investigated from the regression analysis using the measured strains. Finally a new bond strength model is proposed, which is able to predict the relationship for the stress of each direction of CFT column loading on concrete.

Countermeasure and Spalling Property of High Performance Concrete (고성능 콘크리트의 폭렬특성 및 대책)

  • Han, Min-Cheol;Han, Cheon-Goo
    • Proceedings of the Korea Concrete Institute Conference
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    • 2008.04a
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    • pp.1105-1108
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    • 2008
  • This paper investigated measures of spalling prevention and mechanism to secure stability of subjected to a fire circumstance. The results were summarized as following. 1) There were 4 kinds of methods for spalling prevention, such as declining percentage of water content and cement water ratio, isolating from high temperature with fire proof covering, giving lateral resistance stress, and discharging vapor pressure using fibers. 2) It was confirmed that methods using fibers to a new construction and fire proof covering to a existing construction on the basis of investigation for the spalling mechanism through the existing theory of spalling and a new theory of WPB.

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Dynamic Characteristics of Railway Structures under High-Speed Train Loading (고속열차 주행 시 동적하중을 받는 철도구조물의 진동 특성)

  • Rhee, Inkyu;Kim, Jae Min
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.33 no.2
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    • pp.121-128
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    • 2020
  • The purpose of this study is to investigate the distribution patterns of displacement and acceleration fields in a nonlinear soil ground based on the interaction of high-speed train, wheel, rail, and ground. For this purpose, a high-speed train in motion was modeled as the actual wheel, and the vertical contact of wheel and rail and the lateral contact, caused by meandering motion, were simulated; this simulation was based on the moving mass analysis. The soil ground part was given the nonlinear behavior of the upper ground part by using the modified the Drucker-Prager model, and the changes in displacement and acceleration were compared with the behavior of the elastic and inelastic grounds. Using this analysis, the displacement and acceleration ranges close to the actual ground behavior were addressed. Additionally, the von-Mises stress and equivalent plastic strain at the ground were examined. Further, the equivalent plastic and total volumetric strains at each failure surface were examined. The variation in stresses, such as vertical stress, transverse pressure, and longitudinal restraint pressure of wheel-rail contact, with the time history was investigated using moving mass. In the case of nonlinear ground model, the displacement difference obtained based on the train travel is not large when compared to that of the elastic ground model, while the acceleration is caused to generate a large decrease.