• 한국농공학회:학술대회논문집
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• 한국농공학회 1999년도 Proceedings of the 1999 Annual Conference The Korean Society of Agricutural Engineers
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• pp.277-282
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• 1999

Recently , the use of steel fibers has been increased in flexural members and beams of concrete structures ; such as bridge decks, highway roads, runway of airport , buildings , ete.. An experimental investigation of the shear behavior of high-strength reinforced concrete beams using input steel fiber was conducted. However only a few experimental tests have been carried out under static loading . The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking , crack patters, fracture modes. The load versus strain and load versus deflection relation were obtained from the static test.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.245-251
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• 1999

이 연구는 탄소섬유판공법을 사용하여 보강된 철근콘크리트 슬래브에 집중하중 즉 같은 위치에서 휨모멘트와 전단력이 동시에 최대가 되는 경우에 대하여 탄소섬유판의 두께를 변수로 하여 슬래브의 구조적 거동을 실험하였다. 탄소섬유판의 두께에 따른 내력의 차이는 뚜렷이 나타나지 않았으며 이는 보강시험의 주된 파괴가 탄소섬유판의 파단이 아닌 하중점 주위에서의 휨-전단균열에서부터 층분리가 시작되기 때문이다. 그러므로 재하상태에 따른 설계방법을 다르게 할 필요가 있으며, 특히 같은 위치에서 휨 모멘트와 전단력이 최대가 되는 경우 탄소섬유판의 두께는 최대 0.6mm로 하고 무보강슬래브의 휨모멘트에 대한 보강된 슬래브의 휨모멘트는 1.5-2.0으로 제한하는 것이 바람직하다.

• Steel and Composite Structures
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• 제49권4호
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• pp.381-392
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• 2023

This study experimentally investigates the flexural behavior of steel-UHPC composite slabs composed of an innovative negative Poisson's ratio (NPR) steel plate and Ultra High Performance Concrete (UHPC) slab connected via demountable high-strength bolt shear connectors. Eight demountable composite slab specimens were fabricated and tested under traditional four-point bending method. The effects of loading histories (positive and negative bending moment), types of steel plate (NPR steel plate and Q355 steel plate) and spacings of high-strength bolts (150 mm, 200 mm and 250 mm) on the flexural behavior of demountable composite slab, including failure mode, load-deflection curve, interface relative slip, crack width and sectional strain distribution, were evaluated. The results revealed that under positive bending moment, the failure mode of composite slabs employing NPR steel plate was distinct from that with Q355 steel plate, which exhibited that part of high-strength bolts was cut off, part of pre-embedded padded extension nuts was pulled out, and UHPC collapsed due to instantaneous instability and etc. Besides, under the same spacing of high-strength bolts, NPR steel plate availably delayed and restrained the relative slip between steel plate and UHPC plate, thus significantly enhanced the cooperative deformation capacity, flexural stiffness and load capacity for composite slabs further. While under negative bending moment, NPR steel plate effectively improved the flexural capacity and deformation characteristics of composite slabs, but it has no obvious effect on the initial flexural stiffness of composite slabs. Meanwhile, the excellent crack-width control ability for UHPC endowed composite members with better durability. Furthermore, according to the sectional strain distribution analysis, due to the negative Poisson's ratio effect and high yield strength of NPR steel plate, the tensile strain between NPR steel plate and UHPC layer held strain compatibility during the whole loading process, and the magnitude of upward movement for sectional plastic neutral axis could be ignored with the increase of positive bending moment.

• 한국농공학회:학술대회논문집
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• 한국농공학회 2001년도 학술발표회 발표논문집
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• pp.176-180
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• 2001

Steel fiber and polymer are used widely for reinforcement material of RC structures because of its excellences of the durability, serviceability as well as mechanical properties. The purpose of this study is investigate the shear behavior of high concrete beams input polymer-steel fibrous. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. Also, load-strain and load-deflection examined, during the test cracks are sketched the load values according to grow of crack.

• Structural Engineering and Mechanics
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• 제67권2호
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• pp.165-173
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• 2018

A simple predicted model using a modified Shear-lag method was used to represent the moisture absorption effect on the stiffness degradation for $[0/90]_{2s}$ composite laminates with transverse cracks and under flexural loading. Good agreement is obtained by comparing the prediction model and experimental data published by Smith and Ogin (2000). The material properties of the composite are affected by the variation of temperature and moisture absorption. The transient and non-uniform moisture concentration distribution give rise to the transient elastic moduli of cracked composite laminates. The hygrothermal effect is taken into account to assess the changes in the normalised axial and flexural modulus due to transverse crack. The obtained results represent well the dependence of the stiffness properties degradation on the cracks density, moisture absorption and operational temperature. The composite laminate with transverse crack loaded in axial tension is more affected by the hygrothermal condition than the one under flexural loading. Through this theoretical study, we hope to contribute to the understanding of the moisture absorption on the composite materials with matrix cracking.

• Computers and Concrete
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• 제11권1호
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• pp.21-37
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• 2013

High-performance concrete (HPC) usually has higher paste and lower coarse aggregate volumes than normal concrete. The lower aggregate content of HPC can affect the shear capacity of concrete members due to the formation of smooth fractured surfaces and the subsequent development of weak interface shear transfer. Therefore, an experimental investigation was conducted to study the shear strength and cracking behavior of full-scale reinforced beams made with low-cement-content high-performance concrete (LcHPC) as well as conventional HPC. A total of fourteen flexural reinforced concrete (RC) beams without shear reinforcements were tested under a two-point load until shear failure occurred. The primary design variables included the cement content, the shear span to effective depth ratio (a/d), and the tensile steel ratio (${\rho}_w$). The results indicate that LcHPC beams show comparable behaviors in crack and ultimate shear strength as compared with conventional HPC beams. Overall, the shear strength of LcHPC beams was found to be larger than that of corresponding HPC beams, particularly for an a/d value of 1.5. In addition, the crack and ultimate shear strength increased as a/d decreased or ${\rho}_w$ increased for both LcHPC beams and HPC beams. This investigation established that LcHPC is recommendable for structural concrete applications.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.537-542
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• 1999

The design methodologies for carbon fiber sheet(CFS) strengthening of RC structures are not well established yet because the structural behavior of strengthened RC structures is more complex than that of unstrengthened ones. Even though the research for the methods using CFS has beed studied, the strengthening effects and structural behaviors of strengthened structures are not systematized yet. The purpose of this study is to carry out the experimental studies on three kinds of half scale RC slab bridges and to investigate the behavior of RC slab bridges from the experimental results. Typical flexural failure occurs in the non-strengthening slab like general RC slab bridges, and also the flexural failure occurs in the all area strengthened slab with sudden rip-off failure of strengthening material by punching shear. For the case of strip type strengthened slab, flexural failure occurs, with rip-off of second strip at the base of loading point. Strengthening effect on the slab using CFS is that the strength is increased upto 7~15 percent and the crack pattern is changed.

• 한국구조물진단유지관리공학회 논문집
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• 제24권5호
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• pp.1-8
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• 2020

이 연구에서는 철근콘크리트 부재의 전단파괴가 휨-전단 메커니즘에 지배된다는 가정을 바탕으로 인장측과 압축측에 대한 2개의 전단요구곡선들과 이에 대응되는 잠재전단강도곡선들을 각각 도출하였으며, 이를 기반으로 전단강도 산정모델을 제안하였다. 제안모델에서는 철근과 콘크리트의 부착거동을 고려하여 휨균열폭과 철근의 국부응력증가분을 산정하였다. 또한, 휨균열로부터 발전되는 지배전단균열의 생성과 균열진전거동을 이론적으로 모사하기 위하여 균열집중계수를 도입하였으며, 이를 통해 단면높이가 큰 철근콘크리트 부재에서 관측되는 크기효과를 반영하였다. 또한, 기존의 해석모델과는 다르게 전단철근과 콘크리트의 전단기여분 사이의 상호작용을 고려할 수 있는 새로운 형태의 수식을 개발하였다. 제안모델의 검증을 위하여 방대한 전단실험체들을 기존문헌으로부터 수집하였으며, 이를 통해 해석모델을 검증한 결과는 제안모델이 실험체들의 재료, 크기 및 철근의 부착특성에 관계없이 실험결과를 정확하게 평가할 수 있음을 보여주었다.

• 한국구조물진단유지관리공학회 논문집
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• 제1권1호
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• pp.65-73
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• 1997

In this paper, It is the effect of using fiber sheet (Carbon Fiber Sheet & Aramid Fiber Sheet) and Steel Plate for reinforced concrete beam. 25 specimens are tested, 16 specimens are for bending capacity and the other are for shear capacity. In the case of bending testing, the kind and quantity of the reinforcement materials, the bondage and the existence of crack were selected as experimental variables. In the case of shear testing, It is testified the effect of reinforcement with the variables of the method of reinforcement (side type and U type). As a result, Using the reinforcing materials can increase the capacity of bending and shear stress.

• 한국지진공학회논문집
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• 제23권3호
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• pp.183-190
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• 2019

Recent changes in the construction method of piles to minimize noise, along with the development of high-strength reinforcement, have provided an economical high performance RC pile development to compensate for the disadvantages of existing PHC piles. In this study, a methodology for the development of cross - section details of high performance RC piles of various performances is presented by freely applying high strength steel and concrete. This study suggested a technique for calculating bending moments for a given axial force corresponding to the allowable crack widths and this can be used for serviceablity check. In calculating the design shear force, the existing design equation applicable to the rectangular or the I section was modified to be applicable to the hollow circular section. In particular, in the limit state design method, the shear force is calculated in proportion to the axial force, and the procedure for calculating PV diagram is established. Last, the section details are determined through PM diagrams that they have the similar flexural and axial-flexural performances of the PHC pile A, B and C types with a diameter of 500 mm. To facilitate the application of the selected standard sections to the practical tasks, the design PM diagram and design shear forces are proposed in accordance with the strength design method and limit state design method.