• Computers and Concrete
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• 제26권2호
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• pp.137-150
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• 2020

In this paper, the bending behavior of single-walled carbon nanotube-reinforced composite (CNTRC) laminated plates is studied using various shear deformation plate theories. Several types of reinforcement material distributions, a uniform distribution (UD) and three functionally graded distributions (FG), are inspected. A generalized higher-order deformation plate theory is utilized to derive the field equations of the CNTRC laminated plates where an analytical technique based on Navier's series is utilized to solve the static problem for simply-supported boundary conditions. A detailed numerical analysis is carried out to examine the influence of carbon nanotube volume fraction, laminated composite structure, side-to-thickness, and aspect ratios on stresses and deflection of the CNTRC laminated plates.

• Advances in concrete construction
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• 제10권4호
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• pp.289-299
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• 2020

A reliability analysis of the axial compressive load bearing capacity of postfire reinforced concrete (RC) columns strengthened with carbon fiber reinforced polymer (CFRP) sheets was presented. A 3D finite element (FE) model was built for heat transfer analysis using software ABAQUS. Based on the temperature distribution obtained from the FE analysis, the residual axial compressive load bearing capacity of RC columns was worked out using the section method. Formulas for calculating the residual axial compressive load bearing capacity of the columns after fire exposure and the axial compressive load bearing capacity of postfire columns retrofitted with CFRP sheets were developed. Then the Monte Carlo method was used to analyze the reliability of the axial compressive load bearing capacity of the RC columns retrofitted with CFRP sheets using a code developed in MATLAB. The effects of fire exposure time, load ratio, number of CFRP layers, concrete cover thickness, and longitudinal reinforcement ratio on the reliability of the axial compressive load bearing capacity of the columns after fire were investigated. The results show that within 60 minutes of fire exposure time, the reliability index of the RC columns after retrofitting with two layers of CFRPs can meet the requirements of Chinese code GB 50068 (GB 2001) for safety level II. This method is effective and accurate for the reliability analysis of the axial load bearing capacity of postfire reinforced concrete columns retrofitted with CFRP.

• 한국농공학회논문집
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• 제52권4호
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• pp.73-81
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• 2010

The cemented sand and gravel (CSG) method is a construction technique that adds cement and water to rock-like materials, such as rivered gravel or excavation muck which can be obtained easily at areas adjacent to dam sites. This study was performed to evaluate the compaction and compressive strength properties of stress-strain, elastic modulus and fracture mode CSG materials reinforced polypropylene fiber. Polypropylene fiber widely used for concrete reinforcement is randomly distributed into cemented sand. The two types of polypropylene fiber (monofillament and fibrillated fiber) were used and fiber fraction ratio was 0, 0.2 %, 0.4 %, 0.6 % and 0.8 % by the weight of total dry soil. The effect of fiber fraction ratio and fiber shape on compaction and compressive strength were investigated. The optimum moisture contents (OMC) of CSG material increased as fiber fraction increased and the dry density of CSG material decreased as fiber fraction. Also, the maximum increase in compressive strength was obtained at 0.4 % content of monofillament and fibrillated fiber. CSG material behaviour was controlled not only by fiber fraction but also fiber distribution, fiber shape and fiber type.

• Structural Engineering and Mechanics
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• 제64권1호
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• pp.135-143
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• 2017

To upgrade shear performance of reinforced concrete (RC) beams, and particularly of the segments under negative moment within continuous T-section beams, a series of original schemes has been proposed using carbon fibre-reinforced polymer (CFRP) U-shaped strips for shear-strengthening. The current work focuses on one of them, in which CFRP U-strips are wound around steel bars against the top of the flange of a T-beam and then spliced on its bottom face in addition to being bonded onto its sides. The test results showed that the proposed scheme successfully provided reliable anchorage for U-strips and prevented premature onset of shear failure due to FRP debonding. The governing shear mode of failure changed from peeling of CFRP to its fracture or crushing of concrete. The strengthened specimens displayed an average increase of about 60% in shear capacity over the unstrengthened control one. The specimen with a relatively high ratio and uniform distribution of CFRP reinforcement had a maximum increase of nearly 75% in strength as well as significantly improved ductility. The formulas by various codes or guidelines exhibited different accuracy in estimating FRP contribution to shear resistance of the segments that are subjected to negative moment and strengthened with well-anchored FRP U-strips within continuous T-beams. Further investigation is necessary to find a suitable approach to predicting load-carrying capacity of continuous beams shear strengthened in this way.

• The Journal of Asian Finance, Economics and Business
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• 제3권4호
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• pp.81-90
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• 2016

The core purpose of the paper is to explore perceptual displays of rural India towards the role and impact of ICT in transforming the lives through education and telecommunications. After meticulous review of pertinent literature on ICT, and its policy framework, the researcher administers both quantitative and qualitative field data collected from the villages of Andhra Pradesh, Karnataka, Kerala, and Tamil Nadu with a sample of 250 from each state. More than 90 percent of respondents from the four southern states in India clearly thought that the role and impact of ICT is very momentous. Predominantly, cent percent respondents from Kerala evinced that ICT is the major reason for achieving the tag of "100% Literacy State". And also in the remaining three states viz., Andhra Pradesh, Karnataka, and Tamil Nadu, the literacy rate has crossed mind-boggling figures only because of ICT's reinforcement. Even in the arena of telecommunications, these four states average telecom density is more than the country's average. The paper concentrated only on how ICT function empirically to build human capacity in rural south-India through the sectors of only education and telecom. This study is first of its kind and precious to all stakeholders of the ICT sector like educational institutional, telecom firms, customers, employees, and governments, etc.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.422-425
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• 2003

Investigated whether fiber orientation distribution of twisted yarn composites and the fiber content are 0$^{\circ}$ and 90$^{\circ}$ direction tensile strength and some correlation. Tensile strength of 0$^{\circ}$ directions of twisted yarn composites increased changelessly being proportional the fiber content and fiber orientation function get into anisotropic in isotropic. But, tensile strength ratio by separation of fiber filament of 90$^{\circ}$ directions tensile strength decreased when tensile load is imposed for width direction of reinforcement fiber. 0$^{\circ}$ and 90$^{\circ}$ direction tensile strength ratio value of a twisted yarn composites not receive almost effect of the fiber content of fiber orientation function J = 0.4 lows. Although do, 20 wt% of the fiber content is high about 0$^{\circ}$ and 90$^{\circ}$ direction tensile strength ratio about 1.6~2 than 10 wt% from J = 0.4. Therefore. could know that effect of the fiber content is dominate.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.281-287
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• 2003

A Natural cavities were found at shallow depth during construction of a huge bridge in Moon-Kyung, Korea. The distribution patterns of cavities in the Moon-Kyung limestone were investigated carefully with a supplementary field job such as a structural geological survey, a geophysical survey, and a rock mechanical test in laboratory or field. A structural geological mapping produced a detail geological map on this area. It suggested that there were three faults in this area, and these faults had an influence on the mechanism of natural cavities. Among many kinds of geophysical surveys, an electrical resistivity prospecting was applied firstly on the specific area that was selected by results from the geological survey. Many evidences for cavities were disclosed from this geophysical data. Therefore, a seismic tomography was tested on the target area, which was focused by results from the electrical resistivity prospecting and was believed to have several large cavities. A distinct element numerical simulation using the UDEC was followed on the target area after completing all of field surveys. Data from field tests were directly dumped or extrapolated to numerical simulations as input data. It was verified from numerical analysis that several natural cavities underneath the foundation of the bridge should be reinforced. Based on the project result, finally, most of foundations for the bridge were re-examined and the cement grouting reinforcement was constructed on several foundations among them.

• 지질공학
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• 제10권1호
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• pp.79-93
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• 2000

일반적으로 공동 주변에 분포하고 있는 지질구조는 지하 암반 공동 굴착시 지수, 보강, 지하수 유동 등에 상당한 영향을 주게 되므로 지질구조의 분포 및 특성을 아는 것이 매우 중요하다. 본 연구에서는 거제 지역에 기 시행된 지하 비축시설의 조사, 설계 및 시공자료를 토대로 지질구조와 공동 누수량 상호 관계를 분석한 결과, 본역에 발달하고 있는 주 함수구조대의 방향은 N50∼60W, 경사는 거의 수직이며 인장 단열로서 추정된다. 이 구조대는 양수 시험시 타원형의 장축 방향과 일치하고 N10∼30E 방향의 단열들과 교차하고 있으며, 화강섬록암에서 나타나는 전형적인 장방형 단열계를 나타낸다.

• 콘크리트학회논문집
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• 제20권6호
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• pp.681-687
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• 2008

이 연구는 적외선 열화상을 이용하여 철근의 부식을 정량적으로 파악하는 기법을 개발하는 것이다. 연구 진행 과정에서 전기적 가열방법이 실험 데이터에 지대한 영향을 끼치는 것을 발견했다. 가열접촉 방법에 대한 여러 실험적 연구를 통하여 실험 데이터의 신뢰성 확보와 효율적인 연구를 추구하였다. 사각어스클램프를 이용하여 철근을 가열하였을 때 철근의 온도변화를 통해 집게어스클램프보다 표면저항이 적다는 것을 입증하였다. 또한 접촉 방법의 표준화를 위해 토크렌치를 활용한 실험을 진행하였다.

• Smart Structures and Systems
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• 제3권4호
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• pp.475-494
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• 2007

This paper deals with the development of an innovative distributed construction system based on smart prefabricated concrete elements for the real-time condition assessment of civil infrastructure. So far, two reduced-scale prototypes have been produced, each consisting of a $0.2{\times}0.3{\times}5.6$ m RC beam specifically designed for permanent instrumentation with 8 long-gauge Fiber Optic Sensors (FOS) at the lower edge. The sensing system is Fiber Bragg Grating (FBG)-based and can measure finite displacements both static and dynamic with a sample frequency of 625 Hz per channel. The performance of the system underwent validation in the laboratory. The scope of the experiment was to correlate changes in the dynamic response of the beams with different damage scenarios, using a direct modal strain approach. Each specimen was dynamically characterized in the undamaged state and in various damage conditions, simulating different cracking levels and recurrent deterioration scenarios, including cover spalling and corrosion of the reinforcement. The location and the extent of damage are evaluated by calculating damage indices which take account of changes in frequency and in strain-mode-shapes. The outcomes of the experiment demonstrate how the damage distribution detected by the system is fully compatible with the damage extent appraised by inspection.