• Title/Summary/Keyword: concrete filled circular tube

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Fire Resistance of Circular Internally Confined Hollow Reinforced Concrete Column (원형 내부 구속 중공 철근콘크리트 기둥의 내화 성능)

  • Won, Deok-Hee;Han, Taek-Hee;Lee, Gyu-Sei;Kang, Young-Jong
    • Journal of Korean Society of Steel Construction
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    • v.22 no.2
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    • pp.139-150
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    • 2010
  • Reinforced-concrete (RC) columns are frequently designed and constructed. other types of columns includes composite types such as concrete-filled tube columns (CFT). Hollow RC columns may be effective in reducing both the self weight of columns and total amount of materials used. This is due to the fact that a hollow RC column possesses larger moment of inertia than that of solid RC columns of same cross sectional area. Despite the effectiveness the hollow RC column has not been popular because of its poor ductility performance. While the transverse reinforcements are effective in controlling the brittle failure of the outside concrete, they are not capable of resisting the failure of concrete of inner face which is in unconfined state of stress. To overcome these drawbacks, the internally confined hollow reinforced concrete (ICH RC), a new column type, was proposed in the previous researches. In this study, the fire resistance performance of the ICH RC columns was analyzed through a series of extensive heat transfer analyses using the nonlinear-material model program. Also, effect of factors such as the hollowness ratio, thickness of the concrete, and thickness of the internal tube on the fire resistance performance were extensively studied. Then the factors that enhance the fire-resistant performance of ICH RC were presented and analyzed.

Finite Element Analysis of Inelastic Behavior of SRC Composite Piers (SRC 합성교각의 비탄성거동에 대한 유한요소해석)

  • Shim, Chang-Su;Han, Jung-Hoon;Park, Chang-Kyu;Chung, Young-Soo
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 2006.03a
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    • pp.269-275
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    • 2006
  • In the design of bridge piers in seismic area, the ductility requirement is one of the most important design criteria. In order to enhance the seismic performance of RC columns, it is necessary to make the ductility of columns larger by covering RC columns with steel tubes or confining RC columns by arranging transverse reinforcement such as hoop ties closely. Concrete encased composite columns can be utilized for bridge piers especially in seismic area. In this paper, finite element analyses are performed to study the nonlinear behavior of concrete encased composite columns with single core steel or multiple steel elements under static and quasi-static loads. The cross-sections of these specimens ate composed of concrete-encased H-shaped structural steel columns and a concrete-encased circular tube with partial in-filled concrete. Test parameters were the amount of the transverse reinforcement, encased steel member, and loading axis. Through the comparison between FE analyses and test results, adequate material models for confined concrete and unconfined concrete ate investigated. After getting the proper analysis models for composite columns, several parameters are considered to suggest design considerations on the details of composite piers.

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A Study on the fire-resistance of concrete-filled steel square tube columns without fire protection under constant central axial loads

  • Park, Su-Hee;Choi, Sung-Mo;Chung, Kyung-Soo
    • Steel and Composite Structures
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    • v.8 no.6
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    • pp.491-510
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    • 2008
  • This paper presents a plan and guidelines that were drawn for Korean based research carried out on the fire-resistance of CFT columns. This research was carried out by reviewing the Korean regulations related to the fire-resistance of CFT columns and examining studies which had been made in Korea as well as overseas. The first phase of the study plan was to compare the fire-resistance of square CFT columns without fire protection (obtained through fire-resistance tests and numerical analyses) with estimated values (obtained through fire-resistance design formulas proposed in Korea and overseas). This comparison provided conclusions as outlined below. Fire-resistance tests conducted in this study proved that, when the actual design load is taken into consideration, square CFT columns without fire protection are able to resist a fire for more than one hour. A comparison was made of test and analysis results with the fire-resistance time based on the AIJ code, the AISC design formula and the estimation formula suggested for Korea. The results of this comparison showed that the test and analysis results for specimens SAH1, SAH2-1, SAH2-2 and SAH3 were almost identical with the AIJ code, the AISC design formula and estimation formula. For specimens SAH4 and SAH5, the estimation formula was more conservative than the AIJ code and the AISC design formula. It was necessary to identify the factors that have an influence on the fire-resistance of CFT columns without fire protection and to draw fire-resistance design formulas for these columns. To achieve this, it is proposed that numerical analyses and tests be conducted in order to evaluate the fire-resistance of circular CFT columns, the influence of eccentricity existing as an additional factor and the influence of the slenderness ratio of the columns. It is also suggested that the overall behavior of CFT structures without fire protection within a fire be evaluated through analysis simulation.

Development of Connection between CFT Column and Pier Foundation for Top-Down Construction (Top-Down 공사용 원형충전강관기둥과 피어기초의 개발)

  • Jeong, Mee-Ra;Rhim, Hong-Chul;Kim, Seung-Weon;Kim, Dong-Gun;Kang, Seung-Ryong
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2009.05b
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    • pp.29-32
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    • 2009
  • Building foundations for Top-Down construction require a special setting, because the foundations have to be placed way before excavation for the substructure of main building, Usually, the foundation goes into the layer of rock and it is often called rock-pier foundation, Currently, a cage of steel reinforcing bars is inserted to the pre-excavated hole in the rock layer, hanging down from the wide flange steel column above. This paper presents a new method for connecting the prefounded column and the steel cage with a coupler for better connection between the two, The use of a circular Concrete Filled Tube (CFT) as a prefounded column makes it possible to have this type of connection. The details of the connection and application to a Top-Down construction site is also included in this paper.

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A Study on Behavioral Characteristics of Inner Reinforced CFT Column-to-Foundation Connections (내부보강형 CFT 기둥 기초 연결부의 거동특성에 대한 연구)

  • Kim, Hee-Ju;Ham, Jun-Su;Chung, Jin-Il;Hwang, Won-Sup
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.5 no.4
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    • pp.36-43
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    • 2014
  • In this study, circular sectional concrete-filled tube(CFT) column-to-foundation connections were numerically investigated in order to improve their structural details. A inner reinforced specimen with high-tension bolts and inner deformed bars was adopted from a previous experimental study to make the numerical model. The validity of the numerical method was verified through comparing the experimental results with the analysis's ones. In order to optimize design variables about the inner reinforced model, a number of numerical analyses were conducted for various variables. Finally, this study suggested the optimum variables about the reinforced circular sectional CFT column-to-foundation connections.

Experimental and analytical investigations of CFFT columns with and without FRP bars under concentric compression

  • Khan, Qasim S.;Sheikh, M. Neaz;Hadi, Muhammad N.S.
    • Steel and Composite Structures
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    • v.30 no.6
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    • pp.591-601
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    • 2019
  • This research study investigates experimentally and analytically the axial compressive behaviour of Concrete Filled Fiber Reinforced Polymer Tube (CFFT) columns with and without Fiber Reinforced Polymer (FRP) bars. The experimental program comprises five circular columns of 204-206 mm outer diameter and 800-812 mm height. All columns were tested under concentric axial compressive loads. It was found that CFFT columns with and without FRP bars achieved higher peak axial compressive loads and corresponding axial deformations than conventional steel reinforced concrete (RC) column. The contribution of FRP bars was about 12.1% of the axial compressive loads carried by CFFT columns reinforced with FRP bars. Axial load-axial deformation ($P-{\delta}$) curves of CFFT columns were analytically constructed, which mapped well with the experimental $P-{\delta}$ curves. Also, an equation was proposed to predict the axial compressive load capacity of CFFT columns with and without FRP bars, which adequately considers the contributions of the circumferential confinement provided by FRP tubes and lower ultimate strength of FRP bars in compression than in tension.

Cyclic Loading Test for Composite Beam-Column Joints using Circular CEFT Columns (콘크리트피복 원형충전강관 기둥-강재보 접합부에 대한 반복하중실험)

  • Lee, Ho Jun;Park, Hong Gun;Choi, In Rak
    • Journal of Korean Society of Steel Construction
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    • v.29 no.6
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    • pp.411-422
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    • 2017
  • In this study, to investigate the seismic performance of beam-column joints using concrete-encased and -filled circular steel tube(CEFT) columns, two types of tests were performed: (1) column - flange tension test and (2) beam - column joint cyclic load test. In column - flange tension test, test parameters were concrete encasement and connection details: flange width and strengthening rebar. Five specimens were tested to investigate the load-carrying capacity and the failure mode. Test results showed that increase of flange width from 200mm to 350mm result in increase of connection strength and stiffness by 61% and 56%, respectively. Structural performances were further improved with addition of tensile rebars by 35% and 92%, respectively. In cyclic loading test, three exterior beam-column joints were prepared. Test parameters were strengthening details including additional tensile rebars, thickened steel tube, and vertical plate connection. In all joint specimens, flexural yielding of beam was occurred with limited damages in the connection regions. In particular, flexural capacity of beam-column joint was increased due to additional load transfer through tube - beam web connection. Also, connection details such as increase of tube thickness and using vertical plate connection were effective in improving the resistance of panel zone.

An Analytical Study on the Strength Behavior of Column-Foundation Connection with High Tension Bolts (고장력 볼트 기둥-기초 연결부의 강도특성에 관한 해석적 연구)

  • Hwang, Dong A;Hwang, Won Sup;Ham, Jun Su;Jeong, Jin Il
    • Journal of Korean Society of Steel Construction
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    • v.28 no.2
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    • pp.121-128
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    • 2016
  • In order to suggest a reasonable design for the circular concrete filled tube steel column-foundation connection applying high-tension bolts, Overall structural behavior and characteristics according to various variables of column-foundation connection are numerically analyzed using a commercial FE analysis program, ABAQUS. To that goal, finite element analysis is conducted on the basis of the previous study replacing anchor bolts to high-tension bolts, and the analytical results are validated by comparison with experimental results. Also, the various variables(embedded depth and grade of anchor, and height and thickness of rib) involved in behavior of the column-foundation connection are selected through analyzing the current design criteria, and the characteristics of the column-foundation connection are compared and analyzed according to the various variables. In case of the anchor bolts, Applying the high-tension bolts is more advantage and securing the embedded depth beyond 0.5D is recommendable. In case of the rib, a minimum of 0.5D for rib's height and $0.4t_b$ for rib's thickness should be secured to develop the structural performance.