• Architectural research
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• 제8권1호
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• pp.47-56
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• 2006

In this research, the analysis of post-buckling behavior of tapered columns has been performed under a combined load of uniformly distributed axial load along the length and concentric axial load at free end by solving the nonlinear differential equation with the differential transformation technique. The buckling load at various slopes at free end of column is calculated and the results of the analysis using the differential transformation technique is verified with those of previous studies. It is also shown through the results that the buckling load of sinusoidal tapered columns is largest, the linear is second largest, and the parabolic is small in the all ranges of slopes at free end and the deflection of parabolic tapered columns in the x coordinates is largest, the sinusoidal is second largest, and the linear is smallest in the range of slope 0 to 140 degrees at free end. However, when the range of the slope is 160 to 176 degrees at the free end, the deflection of sinusoidal tapered columns in the x coordinates is largest, the linear is second largest, and the parabolic is smallest. In addition, for the linear tapered column, the buckling load increases along with the flexural stiffness ratio. Also, for the parabolic and the sinusoidal tapered column, the buckling loads increase and decrease as the flexural ratios increase in the range of flexural stiffness ratio n = 1.0 to n = 2.0. Through this research, it is verified that the differential transformation technique can be applied to solve the nonlinear differential equation problems, such as analysis of post-buckling behavior of tapered columns. It is also expected that the differential transformation technique apply to various more complicated problems in future.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.475-480
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• 2003

Latex modification of concrete provides the material with higher flexural strength. This increase in flexural strength can attribute to the crack-arresting action of polymer in concrete, and also to the bonding they provide between the matrix and aggregates. This experimental study presents the fracture behavior of 12 flexural reinforced concrete beams repaired or strengthened by latex-modified concrete with the main experimental variables such as overlay thickness, strength thickness, and shear reinforcement. The results are as follow: All beam specimens having shear reinforcement were failed by delamination rupture at concrete interface at about 80% of ultimate loading after flexural cracking. All specimens overlayed and strengthened by latex-modified concrete (LMC) showed higher ultimate flexural strength than OPC control specimen, but lower than LMC control specimen. This increase in flexural strength could attribute to the high bonding they provide between the matrix and aggregates. All specimens except two shear unreinforced showed quite similar and consistent displacement behavior. The effect of overlay and strength thickness on the load-displacement relationship were a small at this study.

• 한국건축시공학회지
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• 제15권3호
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• pp.351-357
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• 2015

Fiber reinforced concrete (FRC) has been successfully used to enhance the flexural toughness of concrete. As fibers are randomly oriented in FRC, they sometimes produce clumps that reduce the mechanical performance, and a properly chosen mixing protocol can be a way to minimize this problem. In this research, the effects of mixing method on the mechanical properties of FRC were investigated. The compressive strength, flexural strength, and flexural toughness were measured using three different mixing methods. It was shown from the results that the compressive strength and peak flexural load were not affected by changes in mixing method. However, in terms of flexural toughness, the changes in mixing method clearly affected the flexural toughness of FRC. The truck-mixed FRC outperformed two pan-mixed FRCs.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.405-411
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• 1998

An iterative numerical computational algorithm is presented to design a plate of shell element subjected to membrane and flexural forces. Based on equilibrium consideration, equations for capacities of top and bottom reinforcements in two orthogonal directions have been derived. The amount of reinforcement is determined locally, i. e., for each sampling point, from the equilibrium between applied and internal forces. One case of design is performed for a hyperbolic paraboloid saddle shell (originally used by Lin and Scordelis) to check the design strength against a consistent design load, therefore, to verify the adequacy of design practice for reinforced concrete shells. Based on nonlinear analyses performed, the analytically calculated ultimate load exceeded the design ultimate load from 14-43% for an analysis with relatively low to high tension stiffening, ${\gamma}$ =5~20 cases. For these cases, the design method gives a lower bound on the ultimate load with respect to Lower bound theorem. This shows the adequacy of the current practice at least for this saddle shell case studied. To generalize the conclusion many more designs-analyses are performed with different shell configurations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.385-390
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• 2001

This paper presents a nonlinear analysis technique with slip, the effects of slip modulus and composite action by shear connector on behavior and capacity in composite structure of sandwich system. As a results of this study, it proved that the slip modulus, in case of shear behavior, seldom influence load-resistance capacity such as yield and ultimate load, but in case of flexural behavior, it appropriately influence load-resistance capacity because of stress redistribution by slip. In case of flexural behavior, analysis result for perfect-composite results in over-estimation and perfect-slip results in under-estimation on behavior and capacity. Therefore, it is desirable to model steel-concrete interface with partial-composite. The effects of slip on behavior and capacity are less in case of positive composite than loosely composite, and it proved that composite action by shear connector improve the load-resistance capacity of this system.

• International Journal of Concrete Structures and Materials
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• 제1권1호
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• pp.45-55
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• 2007

Ten beams bonded with glass fiber reinforced polymer (GFRP) laminates were tested under cyclic loading with the load range and the FRP reinforcement ratio as test parameters. The maximum load level during cyclic loading was 55%, 65% and 75% of the static flexural strength while the minimum load level was kept constant at 35%. Deflections of the beams at the end of 525000 cycles were found to increase by 16% and 44% when the maximum load level was increased from 55% to 65% and 75% of the static flexural strength, respectively. Beams with FRP reinforcement ratios of 0.64% and 1.28% were found to exhibit lesser deflections of about 15% and 20%, respectively, compared to a similar beam without FRP reinforcement. An analytical approach based on cycle-dependent effective moduli of elasticity of concrete and FRP reinforcement is presented and found to predict the deflections of the test beams well.

• 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.

• Computers and Concrete
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• 제15권3호
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• pp.437-459
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• 2015

An experimental investigation on the behaviour of geopolymer composite concrete beams reinforced with conventional steel bars and various types of fibres namely steel, polypropylene and glass in different volume fractions under flexural loading is presented in this paper. The cross sectional dimensions and the span of the beams were same for all the beams. The first crack load, ultimate load and the loaddeflection response at various stages of loading were evaluated experimentally. The details of the finite element analysis using "ANSYS 10.0" program to predict the load-deflection behavior of geopolymer composite reinforced concrete beams on significant stages of loading are also presented. Nonlinear finite element analysis has been performed and a comparison between the results obtained from finite element analysis (FEA) and experiments were made. Analytical results obtained using ANSYS were also compared with the calculations based on theory and presented.

• 콘크리트학회논문집
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• 제11권3호
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• pp.69-80
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• 1999

The strengthening of reinforced concrete structures by externally bonded GFRP has become increasingly common in resent years. However the analysis and design method for GFRP plate strengthening of RC beams is not well established yet. The purpose of present paper is, therefore, to define the failure mechanism and failure behavior of strengthened RC beam using GFRP and then to propose a resonable method for the calculation of interface debonding load for those beams. From the experimental results of beams strengthened by GFRP, the influence of length and thickness, width of plate on the interfacial debonding failure behavior of beam is studied and, on the basis of test results, the semi-empirical equation to predict debonding load is developed. The proposed theory based on nonlinear analysis and critical flexural crack width, predicts relatively well the debonding failure load of test beams and may be efficiently used in the analysis and design of strengthened RC beams using GFRP.

• 한국강구조학회 논문집
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• 제27권6호
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• pp.525-536
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• 2015

콘크리트피복 충전강관의 휨-압축 성능을 평가하기 위한 편심압축실험을 수행하였다. 기둥 주철근의 국부좌굴을 구속하고 콘크리트피복의 조기파괴를 방지하기 위하여 U형 띠철근 상세를 제안하였다. 주요 실험변수는 축하중 편심거리, 띠철근 간격, 그리고 콘크리트피복 여부이다. 실험결과 얇은 콘크리트피복에 수직균열이 조기에 발생하였지만 실험체의 최대강도는 콘크리트 피복의 기여도를 고려한 예측강도를 만족하였다. 또한, 내부 원형강관으로 인하여 제안된 콘크리트피복 충전강관은 우수한 변형능력을 나타냈다. 실험체의 휨-압축 강도 및 휨강성을 현행 설계기준과 비교하여 분석하였다.