• Title/Summary/Keyword: concrete filled circular steel tube

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Axial Loading Behaviors and ACI 440 Code Applied Ultimate Axial Strength Formula of CFRP Strengthened Circular CFT Columns (탄소섬유쉬트로 보강된 원형CFT기둥의 압축거동과 ACI 440 code를 응용한 압축내력예측식 제안)

  • Park, Jai-Woo;Hong, Young-Kyun;Choi, Sung-Mo
    • Journal of the Korean Society for Advanced Composite Structures
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    • v.2 no.1
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    • pp.23-29
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    • 2011
  • This study investigates the axial behavior of CFRP strengthened circular CFT columns and proposes the design formula of CFRP strengthened circular CFT columns. 10 specimens were prepared and axial loading test were conducted to investigate the retrofitting effects of CFRP composites on CFT columns. The main parameters are the number of FRP sheets and D/t ratio. Test results showed that the CFRP retrofitting enhanced the load bearing capacity of the circular CFT columns. Finally, A ACI 440 code applied ultimate axial strength formula is proposed to predict the ultimate strength of CFRP strengthened circular CFT columns. The proposed formula are good agreement with the test results.

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.

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.

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.