• Structural Engineering and Mechanics
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• 제84권2호
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• pp.239-251
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• 2022

The use of lateral reinforcement in confined concrete columns can improve bearing capacity and deformability. The lateral responses of lateral reinforcement significantly influence the effective confining pressure on core concrete. However, lateral strain-axial strain model of concrete columns confined by lateral reinforcement has not received enough attention. In this paper, based on experimental results of 85 concrete columns confined by lateral reinforcement under axial compression, the effect of unconfined concrete compressive strength, volumetric ratio, lateral reinforcement yield strength, and confinement type on lateral strain-axial strain curves was investigated. Through parameter analysis, it indicated that with the same level of axial strain, the lateral strain slightly increased with the increase in the unconfined concrete compressive strength, but decreased with the increase in volumetric ratio significantly. The lateral reinforcement yield strength had slight influence on lateral strain-axial strain curves. At the same level of lateral strain, the axial strain of specimen with spiral was larger than that of specimen with stirrup. Furthermore, a lateral strain-axial strain model for concrete columns confined by lateral reinforcement under axial compression was proposed by introducing the effects of unconfined concrete compressive strength, volumetric ratio, confinement type and effective confining pressure, which showed good agreement with the experimental results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.191-196
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• 2001

The structural performance of a shear wall subjected to lateral loads is influenced by many factors, such as sectional shape, aspect ratio, vertical and horizontal reinforcement, lateral confinement and axial compression, etc. This experimental research is focusing to investigate the structural performance of T-shaped walls with different confining reinforcement. Experimental results show that all specimens finally failed by the crushing of the concrete in the compression zone. Although the location and content of the lateral confinement is different, the results are very similar during the negative loading direction where the flange is compressed. However, when flange is subjected to tension, the location and content of the lateral confinement results in a large difference in the structural performance of T-shaped walls. Therefore, selection of location and content of the lateral confinement would be important aspect in the design of the nonsymmetric structural walls.

• 콘크리트학회논문집
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• 제17권5호
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• pp.843-852
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• 2005

Presently, test results and stress-strain models for poorly confined high-strength columns, more specifically for columns with a tie volumetric ratio smaller than $2.0\%$, are scarce. This paper presents test results loaded in axial direction for square reinforced concrete columns confined by various volumetric ratio lateral ties including low-volumetric ratio. Test variables include concrete compressive strength, tie yield strength, tie arrangement type, and tie volumetric ratio. Local strains measured using strain gages bonded to an acryl rod. For square RC columns confined by lateral ties, the confinement effect was efficiently improved by changing tie arrangement type from Type-A to Type-B. A method to compute the stress in lateral ties at the concrete peak strength and a new stress-strain model for the confined concrete are proposed. Over a wide range of confinement parameters, the model shows good agreement with stress-strain relationships established experimentally.

• 콘크리트학회논문집
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• 제12권4호
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• pp.3-14
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• 2000

Structural performance of the walls subjected to lateral load reversals depends on various parameters such as loading history, sectional shape, reinforcement, lateral confinement, aspect ratio, axial compression, etc. Thus, the performance of the shearwall for wall-type apartment should be evaluated properly considering above parameters. This study investigates the effect of sectional shape on the structural performance of the wall. Sectional shape of the specimen is rectangular, barbell and T. Based on this experimental results, all specimens behaved as ductile fashion and failed by concrete crushing of the compression zone. Deformation index of those specimens evaluated better than 3 of ductility ratio, and 1.5% of deformability specified by seismic provision. Moreover, the performance of the rectangular shaped specimen, whose compression zone was confined with U-bar and cross tie, was as good as the barbell shaped specimen. Therefore, if we considered construction practice such as workmanship and detailing, shearwall with rectangular section may be more economical lateral load resisting system.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.305-308
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• 2008

이 연구에서는 최근 연구가 활발히 진행되고 있는 조립식 프리캐스트 세그먼트 콘크리트 교각공법에서 사용되어지는 기성 콘크리트 세그먼트의 횡 방향 구속철근에 의한 구속효과에 대한 연구를 수행하였다. 일반적으로 횡방향 구속철근에 의한 콘크리트의 구속효과는 구속효과계수에 의하여 결정되며 구속효과계수는 유효 구속 콘크리트 단면적과 구속 콘크리트 단면적의 비로서 결정된다. 유효 구속 콘크리트 단면적은 횡 방향 구속철근간의 간격에서 발생하는 Arching action에 의하여 결정되어지며 구속 콘크리트 단면적은 교각의 주철근비에 의하여 결정되어진다. 그러나 프리캐스트 콘크리트 세그먼트의 경우 세그먼트 상, 하부에 존재하는 피복을 고려하여야 한다. 즉 최상단 및 최하단에 배근되는 횡방향 구속철근에서 상, 하부 콘크리트 표면의 피복까지의 구속효과를 고려하여야 한다. 이 연구에서는 이에 대한 고려 방법을 제안하였다. 제안한 프리케스트 구속효과를 고려한 콘크리트 재료 모델을 RCAHEST에 적용하여 그 타당성을 검증하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제6권2호
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• pp.245-253
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• 2002

This study was focused on the effect of concrete strength and lateral ties of concrete columns using high-strength concrete. Thirty-six concrete columns with 20cm square cross-section were tested. Experimental parameters included the concrete strength, the distribution of longitudinal bars and the volumetric ratio, yield strength, spacing of lateral ties. From the experiments, we found that: 1) the increasing rate of the strength and ductility of concrete columns caused by confinement of lateral ties was decreasing, as the concrete strength increased. 2) The high volumetric ratio and the reduction of tie spacing had a tendency to enhance the strength and improve the ductility. 3) The high-strength concrete columns required high volumetric ratio of lateral ties to maintain the proper strength and ductility. It was observed that the current AIK design code to specify the maximum tie spacing of high-strength concrete columns led to the poor strength and ductility for seismic design.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.563-568
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• 2002

This paper is a fundamental study on the mechanical properties of the high performance concrete confined with metal lath, glass and carbon fiber laterally. According to the results, it shows that the compressive strength increases by 9%, 8% and 6% in metal lath carbon fiber and glass fiber in case of W/B 30% respectively. In case of W/B 30% and 40%, flecxural strength shows largely in order of carbon fiber, metal lath, glass fiber. In strain-stress curve with the kinds of material for lateral confinement, while brittleness failure occurs in plain concrete just after maximum load, it is improved in some degree in confined concrete due to increase of the strain by increase of toughness. But, elastic modulus shows the similar tendency between confined concrete and plain concrete. Length change ratio by drying shrinkage shows little a bit in order of carbon fiber, glass fiber and metal lath due to confinement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.403-408
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• 2003

The objective of this study is to understand the variables affected the confinement for the transverse reinforcement of the reinforced concrete structural walls with the T-shaped cross section subjected to cyclic lateral loads. The structural performance of T-shaped walls was advanced by the transverse reinforcement which restrained the concrete subjected to compressive stress. If the arrangement of transverse reinforcement was not suitable for the confinement, T-shaped walls happened the brittle failure by web crushing or bucking of vertical reinforcement at the compression zone. It is necessary to confine transverse reinforcement in order to prevent the these failure. But the location of neutral axis and the magnitude of ultimate strain vary according to the section shape, a ratio of axial load, a ratio of wall cross sectional area to the floor-plan area, an aspect ratio and the reinforcement ratio. Therefore, the objective of this research is to grasp the location of neutral axis and the range which needs for the confinement of transverse reinforcement through the results of the sectional analysis which varies the ratio of axial load and the ratio of vertical reinforcement.

• 콘크리트학회논문집
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• 제15권6호
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• pp.877-887
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• 2003

구조벽의 성능에 기초한 내진설계를 위해서는 변형요구량을 만족시킬 수 있도록 구조벽의 횡보강 길이 및 보강상세를 결정하는 합리적인 설계 방법이 필요하다. 이를 위하여, 다양한 설계변수를 고려하여 단부 횡보강된 구조벽의 최대곡률성능을 정의하였고 벽체의 형상, 설계변위에 따른 곡률요구량을 정의하였다. 벽체의 곡률성능과 요구량을 등가로 하여 벽체 단부의 횡보강길이를 산정할 수 있는 방법을 제안하였다. 본 방법에 의하면 단부횡보강길이는 압축력과 설계변위가 증가하면 늘어나고 콘크리트 강도, 벽체두께, 횡보강효과, 형상비가 커지면 줄어든다. 또한 효율적인 단부 횡보강 효과와 시공성을 확보하기 위해서 단부 횡보강상세에 대한 연구를 수행하였으며 이 연구결과를 근거로 효율적인 횡보강근의 배치간격에 대한 합리적인 지침을 제안하였다.

• Earthquakes and Structures
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• 제7권5호
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• pp.667-689
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• 2014

Structural walls (also known as shear walls) are one of the common lateral load resisting elements in reinforced concrete (RC) buildings in seismic regions. The performance of RC structural walls in recent earthquakes has exposed some problems with the existing design of RC structural walls. The main issues lie around the buckling of bars, out-of plane deformation of the wall (especially the zone deteriorated in compression), reinforcement getting snapped beneath a solitary thin crack etc. This study compares performance of a typical wall designed by different standards. For this purpose, a case study RC shear wall is taken from the Hotel Grand Chancellor in Christchurch which was designed according to the 1982 version of the New Zealand concrete structures standard (NZS3101:1982). The wall is redesigned in this study to comply with the detailing requirements of three standards; ACI-318-11, NZS3101:2006 and Eurocode 8 in such a way that they provide the same flexural and shear capacity. Based on section analysis and pushover analysis, nonlinear responses of the walls are compared in terms of their lateral load capacity and curvature as well as displacement ductilities, and the effect of the code limitations on nonlinear responses of the different walls are evaluated. A parametric study is also carried out to further investigate the effect of confinement length and axial load ratio on the lateral response of shear walls.