• Steel and Composite Structures
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• 제31권1호
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• pp.69-83
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• 2019

This paper investigates the structural behavior of very high strength concrete encased steel composite columns via combined experimental and analytical study. The experimental programme examines stub composite columns under pure compression and eccentric compression. The experimental results show that the high strength encased concrete composite column exhibits brittle post peak behavior and low ductility but has acceptable compressive resistance. The high strength concrete encased composite column subjected to early spalling and initial flexural cracking due to its brittle nature that may degrade the stiffness and ultimate resistance. The analytical study compares the current code methods (ACI 318, Eurocode 4, AISC 360 and Chinese JGJ 138) in predicting the compressive resistance of the high strength concrete encased composite columns to verify the accuracy. The plastic design resistance may not be fully achieved. A database including the concrete encased composite column under concentered and eccentric compression is established to verify the predictions using the proposed elastic, elastoplastic and plastic methods. Image-oriented intelligent recognition tool-based fiber element method is programmed to predict the load resistances. It is found that the plastic method can give an accurate prediction of the load resistance for the encased composite column using normal strength concrete (20-60 MPa) while the elastoplastic method provides reasonably conservative predictions for the encased composite column using high strength concrete (60-120 MPa).

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.185-190
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• 1992

ACI318-89 Recommended that when the specified compressive strength of concrete in a column is greater than1.4 times that specified for a floor system, top surface of the column concrete shall extend 2ft(600mm)into the slab from the face of column to avoid unexpected brittle failure. The major variables are extension distance, flexural strength ratio(Mr), and shear reinforcement ratio(Vs). Test results are as follows ; (1) The failure modes of specimens under cyclic loading were concentrated at critical region from beam-column joint face. (2) Ductility index($\mu$f) were increased with increasing of shear confinement ratio and flexural strength ratio. (3)The specimens with 2ft extension distance showed more ductility than the specimens with 1ft extension distance.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.1091-1096
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• 2003

Pullout tests of single headed bars using plain concrete blocks indicate that the embedment depth of $10d_b$ is in general required for the headed bars to develop pullout strength equivalent to 125% of bar yield strength. In this experimental study, test results of multiple headed bars installed in reinforced concrete column sections are presented. Test variables included embedment depth, column main reinforcement ratio, and spacing of column ties. 2D29 bars were pulled out at one time from normal strength concrete. Test results indicated that the embedment depths, column tie spacings, and column main reinforcement ratios all influenced the pullout strengths of the headed bars. When the embedment depth was not sufficient, narrow tie spacings especially resulted in increased pullout strengths of the headed bars. Test results also indicated that the embedment depth of 15㏈ was sufficient for the closely spaced two headed bars (head-to-head spacing =$6d_b$) to develop pullout strength equivalent to 125% of the bar yield strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.468-474
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• 1997

High strength concrete is a more effective material for columns subject to axial force and moment than for other structural elements. The purpose of this study is to review strength calculation methods for high strength concrete columus by comparison of analytical values and experimental results. The variables of column test under eccentric loading were concrete compressive strength, longitudinal steel ratio, and eccentricity of load. The tied column sections of 120×120mm and 210×210mm were tested and the eccentricity of load varied in the range from 0.16 times to 0.54 times the column depth. The analytical results using the stress-strain relationship to 0.54 times the column depth. The analytical results using the stress-strain relationship as well as the ACI's rectangular block, Zia's modified block, and the trapezoidal block are compared with experimentally obtained data, and discussed in this paper.

• Structural Engineering and Mechanics
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• 제41권3호
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• pp.421-440
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• 2012

In this analytical study numerous prior experimental studies on reinforced concrete beam-to-column connections subjected to cyclic loading are investigated and a database of geometric properties, material strengths, configuration details and test results of subassemblies is established. Considering previous experimental research and employing statistical correlation method, parameters affecting joint shear capacity are determined. Afterwards, an equation to predict the joint shear strength is formed based on the most influential parameters. The developed equation includes parameters that take into account the effect of eccentricity, column axial load, wide beams and transverse beams on the seismic behavior of the beam-to-column connections, besides the key parameters such as concrete compressive strength, reinforcement yield strength, effective joint width and joint transverse reinforcement ratio.

• Steel and Composite Structures
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• 제20권4호
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• pp.851-867
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• 2016

Cruciform sections are an appropriate option for columns of orthogonal moment resisting frames for equal bending strength and stiffness about two main axes and the implementation is easier for continuity plates. These columns consist of two I-shaped sections, so that one of them is cut out in middle and two generated T-shaped sections be welded into I-shaped profile. Furthermore, in steel moment frames, unbalance moment at the beam-column connection leads to shear deformation in panel zone. Most of the obtained relations for panel zone strength derived from experimental and analytical results are on I-shaped columns with almost thin flanges. In this paper, a parametric study has been carried out using Finite Element Method (FEM) with effective parameters at the panel zone behavior. These parameters consist of column flange thickness, column web thickness, and thickness of continuity plates. Additionally, a mathematical model has been suggested to determine strength of cruciform column panel zone and has been shown its accuracy and efficiency.

• 한국강구조학회 논문집
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• 제21권5호
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• pp.461-470
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• 2009

기둥은 축하중과 지진하중에 저항하는 주부재로서 구조물에서 가장 중요한 부재중의 하나이다. 이러한 기둥은 화재 시 고온에 의해 그 성능이 저하되어 전체 구조물계에 심각한 균열을 초래할 수 있으며, 구조물의 붕괴로도 이어질 수 있다. 본 연구에서는 새로운 형식의 기둥인 내부구속 중공 콘크리트 충전강관 기둥 (ICH CFT column; Internally Confined Hollow Concrete Filled Tube column)의 내화 성능이 연구되어져 있지 않기 때문에 건축물에 적용을 하여 기준에 맞는 기둥을 만들기 위해서는 내화 성능 평가가 필요하다. 본 기둥은 콘크리트 충전 강관 기둥 (CFT column; Concrete Filled Tube column)과 같이 외부 강관에 의해 콘크리트가 구속되어 기둥의 성능을 발휘하므로, 외부 강관의 항복 여부가 전체 기둥의 강도를 결정하게 될 것이다. 그래서 본 연구에서는 화재에 의한 기둥의 온도 변화에 따른 ICH CFT 기둥의 강도를 콘크리트의 구속효과와 재료비선형성을 고려하여 해석을 수행하였고, 또한 기둥의 중공비, 외부강관의 두께, 콘크리트의 강도를 매개 변수로 선정하여 기둥의 내화 성능을 평가하였으며, 해석에는 범용 프로그램과 전용 프로그램을 병행하여 사용하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.582-588
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• 1998

The experimental study for the interior beam-column joint for high strength conccrete using Belite cement is presented. Test parameters are compressive strength, flexual strength ratio and joint shear stresslevel. The results from cyclic loading tests show different behaviors from the various parameters. Also, The different behaviors on beam-column joint can be achived by the different concrete strength.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.177-178
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• 2017

The beam-column connection using high-strength GFRP bars exhibited a comparable flexural strength but brittle failure mode, when compared with those of connection using high-strength steel reinforcement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.493-498
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• 2002

An experimental investigation was conducted to study the behavior of high-strength RC wide beam-column joints with slab subjected to reversed cyclic loads under constant axial load. Six half scale interior wide beam-column assemblies representing a portion of a frame subjected to simulated seismic loading were tested, including three specimens without slab and three specimens with slab. The primary variables were compressive strength of concrete( $f_{ck}$ =240, 500kgf/c $m^2$), the ratio of the column-to-beam flexural capacity( $M_{r}$=2$\Sigma$ $M_{c}$$\Sigma$ $M_{b}$ ; 0.77-2.26), extended length of the column concrete($\ell$$_{d}$ ; 0, 9.6, 30cm), ratio of the column-to-beam width(b/H ; 1.54, 1.67). Test results are shown that (1) the behavior of specimen using high-strength concrete satisfied the required minimum ductile capacity according to increase the compressive strength, (2). In the design of the wide beam-column joints, one should be consider the effects of slab stiffness which is ignored in the current design code and practice.ice.e.e.