• 한국농공학회논문집
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• 제61권3호
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• pp.43-53
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• 2019

It is well-known fact that the stone-mastic asphalt (SMA) mixture has shown superior rut resistance, compared with the dense-graded asphalt (DGA) mixture in highway pavements. However, the SMA is measured to be inferior to DGA mixes when tested by well-known high-temperature test methods, such as the wheel tracking (WT), asphalt pavement analyzer, the Marshall Stability and Kim Test. Therefore, this study examined the reasons why it was measured to be inferior, and devised a potential procedure by which the superiority of SMA could be measured at $60^{\circ}C$. The strength against deformation ($S_D$), which was known to show very high correlation with WT results for DGA mixes, was measured by the Kim Test on the specimen confined in the compacted mold. In standard Kim Test, which used the specimen without confinement, the DGA was measured to show higher $S_D$ than the SMA. But by confining specimen, it was found that the $S_D$ of SMA was measured to be higher than that of DGA. Therefore, the confined static test protocol devised in this study was found to be feasible for evaluating rut resistance of SMA mix.

• 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 1993년도 봄 학술발표회 논문집
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• pp.119-123
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• 1993

Axial load-strain relationships of confined concrete with spiral reinforcement were investigated. The main variables were compressive strength of concrete, spacing of hoop reinforcement, and specimen height of plain concrete. The program included tests of eleven confined specimens, and twelve plain specimens, but for all specimens no longitudinal reinforcement was provided. Load-strain curves of confined and plain concrete specimens are reporeted.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.487-492
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• 2003

High-strength concrete(HSC) is a new construction material with enormous potential. Structures using high-strength concrete are to be coming more and more popular. But high-strength reinforced concrete columns show brittle behavior. It, therefore, is necessary to improve the ductility of HSC members. The purpose of this study is to investigate the ductility and strength of high-strength columns with variable lateral confinement under concentric axial load. Five HSC columns with compressive strength 68㎫ are designed with variable lateral confinements such as carbon fiber sheet(CFS), glass fiber sheet(GFS), and metal lath. Test results indicate that specimen confined by CFS show 11% higher maximum strength, 2.74 times ductility than A specimen using hoop. On comparing with the specimen A and B confined metal lath instead of hoop, strength decrease of 3%, and ductility increase of 1.21 times were observed.

• 한국구조물진단유지관리공학회 논문집
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• 제5권2호
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• pp.93-102
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• 2001

The objective of this experimental study is to evaluate the strengthening effects of concrete compression confined with Epoxy-boned compound fiber sheets. An analytical model is proposed to construct a stress-strain relationship for confined concrete. Test results are summarized as followed. While non-FRP lateral confinement specimens appeared sudden failure after shell concrete was torn off, specimens confined laterally with FRP were showed that their failure. Specially, Glass fiber lateral confined specimens occurred obviously increase ductility ability. Hence, concrete specimen with lateral confinement by Hi-carborn and Aramide. Glass fiber simultaneously can be increased in not only strength but also a lot of ductility ability.

• International Journal of Concrete Structures and Materials
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• 제5권1호
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• pp.49-55
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• 2011

The main objective of this investigation is to study size effect on compressive strength of CFRP confined concrete cylinders subjected to axial compressive loading. In total 24 concrete cylinders with different sizes were tested, small specimens with a diameter of 100 mm and a height of 200 mm, medium specimens with a diameter of 200 mm and a height of 400 mm, and big specimens with a diameter of 300 mm and a height of 600 mm. The lateral confining pressure of each specimen is the same and from that hypothesis the small specimens were confined with one layer of CFRP, medium and big specimens were performed by two and three layers of CFRP respectively. Test results indicate a significant enhancement in compressive strength for all confined specimens, and moreover, the compressive strengths of small and medium specimens are almost the same while a bit lower for big specimens. These results permit to conclude that there is no size effect on compressive strength of confined specimens regardless of cylinder dimension.

• 콘크리트학회지
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• 제10권6호
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• pp.345-352
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• 1998

본 연구에서는 에폭시 모르터를 접착제로 사용한 탄소섬유판 접착공법을 사용하여 철그콘크리트 구조물의 주요부재인 압축부재를 간격, 두께, 폭, 겹수 및 이음길이의 변수로 하여 횡보강한 콘크리트 압축부재의 구조적 거동에 관한 연구를 실험적으로 진행하였다. 파괴양상은 보강된 시험체 모두가 보강재인 탄소섬유판의 인장파단과 동시에 급작스러운 취성파괴로 파괴를 보여주었다. 연구결과 압축부재 시험체를 동일한 조건으로 횡보강할 경우, 시험체의 지름에 대한 길이의 비가 다르더라고 횡보강도니 시험체의 구조적 거동은 같게 나타났다. 압축부재 시험체의 보강효과는 보강재의 간격이 좁을수록 동일하중에서의 변위는 작아지고, 연성이 커지는 것으로 나타났으며, 보강재의 폭이 다르더라도 보강량과 보강겹수가 같으면 횡보강효과는 거의 같은 것으로 나타났다. 또한 횡보강 시, 보강재 두께가 증가하면 그와 비례하여 횡보강효과도 증가하는 것으로 나타났다. 보강재의 겹수가 증가할 경우 보강재 겹수 증가에 의한 보강효과 증가는 비례적이지 않을 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.743-749
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• 1999

Recently new rehabilitation techniques have been proposed with advanced composite materials like carbon fiber, aramid, glass fiber sheet and so forth. The purpose of this paper is to investigate the mechanical characteristics of reinforced concrete columns confined with carbon fiber sheet and evaluate the degree of their strengthening effect. For the test, the specimen size of column is 15cm$\times$15cm$\times$90cm reinforced with 4 number of main bars of 10 mm diameter, tied bars of 6 mm diameter and slenderness ratio 20. Columns were wrapped with carbon fiber sheet along the column length. It is necessary to make some assumption regarding the confinement of carbon fiber sheet to apply to reinforced concrete columns under concentric loads. The strength gain effect of columns confined with carbon fiber sheet could be predicted using the proposed equation.

• Computational Structural Engineering : An International Journal
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• 제1권1호
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• pp.39-48
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• 2001

An analytical compressive stress-strain relationship model for circular and rectangular concrete specimens confined with laminated carbon fiber sheets (CFS) is studied. Tsai-Hill and Tsai-Wu failure criteria were used to implement orthotropic behavior of laminated composite materials. By using these criteria, an algorithm which analyzes the confinement effect of CFS on concrete was developed. The proposed analytical model was verified through the comparison with experimental data. Various parameters such as concrete strength, ply angle, laminate thickness, section shape, and ply stacking sequences were investigated. Numerical results by the proposed model effectively simulate the experimental compressive stress-strain behavior of CFS confined concrete specimens. Also, the pro-posed model estimates the compressive strength of the specimen to a high degree of accuracy.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.5-8
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• 2004

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of four one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The constant vertical axial stresses applied are 0, 0.84 and 1.80MPa, while the amount of reinforcements in horizontal and vertical directions are $0\%,\;0.08\%\;and\;0.18\%$ respectively. Test results obtained for each specimen include cracking patterns, load-deflection data, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.