• Smart Structures and Systems
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• v.14 no.5
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• pp.785-809
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• 2014

In this paper, an Adaptive nerou-based inference system (ANFIS) is being used for the prediction of shear strength of high strength concrete (HSC) beams without stirrups. The input parameters comprise of tensile reinforcement ratio, concrete compressive strength and shear span to depth ratio. Additionally, 122 experimental datasets were extracted from the literature review on the HSC beams with some comparable cross sectional dimensions and loading conditions. A comparative analysis has been carried out on the predicted shear strength of HSC beams without stirrups via the ANFIS method with those from the CEB-FIP Model Code (1990), AASHTO LRFD 1994 and CSA A23.3 - 94 codes of design. The shear strength prediction with ANFIS is discovered to be superior to CEB-FIP Model Code (1990), AASHTO LRFD 1994 and CSA A23.3 - 94. The predictions obtained from the ANFIS are harmonious with the test results not accounting for the shear span to depth ratio, tensile reinforcement ratio and concrete compressive strength; the data of the average, variance, correlation coefficient and coefficient of variation (CV) of the ratio between the shear strength predicted using the ANFIS method and the real shear strength are 0.995, 0.014, 0.969 and 11.97%, respectively. Taking a look at the CV index, the shear strength prediction shows better in nonlinear iterations such as the ANFIS for shear strength prediction of HSC beams without stirrups.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.403-406
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• 2005

This paper deals with the propriety of the shear test data with stirrup reported in ACI and ASCE structural journal and the shear resistance characteristics affected by compressive strength of concrere($f_{ck}$), shear span-to-depth ratio (a/d), tensile reinforcement ratio($\rho$), and shear reinforcement ratio($rho_{v}$). The analysis was accomplished by the 242 shear test data. The test data include the flexural failure data around 40$\%$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.5 no.3
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• pp.181-189
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• 2001

Recently, the need for strengthening reinforced concrete(R.C.) structure has been increased, particularly when there is an increase in load requirements, a change in use, a degradation problem, or design/construction defects. The use of composite materials for structural repair presents several advantages and has been investigated all over the world. It is well known that the incorporation of carbon fiber sheet(CFS) with concrete is one of the most effective ways to strengthen the R.C. structure. In this papers, experimentally investigated the ductile behavior of the R.C. beams strengthened with CFS, and provided the basic data for design of R.C. beams strengthened with CFS. Tests were carried out with 15 beams ($20cm{\times}30cm{\times}240cm$) reinforced with CFS, and with parameters including and the ratio of tensile reinforcement to that of balanced condition and number of CFS. The results show that strengthened and non-strengthened beams exhibit different ductile behovior. Non-strengthened beams showed increase of ductility as amount of the tensile reinforcement decreased. However, bearing capacity of the CFS-strengthened beams are dictated by the strength of the CFS layers that a very high ductility is indicated for the beams with large number of CFS.

• Journal of the Korean Institute of Landscape Architecture
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• v.27 no.5
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• pp.80-93
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• 2000

This study measured the shearing resistance of the roots of the Pinus Koraiensis by the tensile strength gained through their individual tensile test for the Root Reinforcement Model. On the basis of the shearing resistance value calculated through such a process the factor of safety(Fs) was comparatively presented by using the simplified Janbu Method in PCSTABL5M, the slop-analyzing software which had been developed in Purdue University of the U.S.A according to the shape of a slope and the type of soil. The results to have measured a stress and the factor of safety(Fs) by experiment are as follows. 1) The mean root diameter of the Pinus Koraiensis used for this experiment was 2.483mm and the mean tensile stress was calculated as 422.846(kgf/$\textrm{cm}^2$). In the strain ratio of material and the elastic modulus was measured 7.8%, 9,291.92(kgf/$\textrm{cm}^2$). 2) The shearing strength including the resistance of soil and root is expressed as Rt=C+Cr+$\sigma$.tan . ΔCr(kg/$\textrm{cm}^2$) of the shearing resistance calculated by estimating the areal ratio of roots at 10 is 0.253(kgf/$\textrm{cm}^2$). 3) As the result of making an analysis of the natural slope stability by the soil parameter, the factor of safety(Fs) was calculated at 1.795 in CL, and the stability analysis of the root reinforcement slope, Fs was calculated at 1.952. However, since a precise analysis of the controlled factors of the slope analyses are demanded for more accurate dynamic analyses, the future demands a study on this.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.2
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• pp.117-126
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• 2020

The main objective of this experimental study is to investigate shear strength of reinforced concrete beams according to longitudinal reinforcement ratio (ρ) and size effect. In order to find out the shear strength according to the tensile reinforcement ratio, in particular, the main variables are 100%, 75% and 50% of ρ=0.01 which is widely used in construction field. A total of twelve RC beams were tested under 4-point loading conditions. In addition to the existing proposal equations, the theoretical values such as KBC and ACI equations are compared with the experimental data. Through this analysis, this study is designed to provide more reasonable equations for shear design of reinforced concrete beams. When shear reinforcement bar spacing of nine specimens (R^*-1, R^*-2, and R^*-3 series) fixed as d/s=2.0 and three specimens of R^*-4 series fixed as d/s=1.5 are compared, the shear strength of two groups showed similar values. As a result, the current standard of d/s=2.0 for shear reinforcement bar spacing may be somewhat alleviated.

• Magazine of the Korean Society of Agricultural Engineers
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• v.29 no.4
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• pp.124-131
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• 1987

The aims of this study was to determine the mechanical properties of steel-fiber reinforced concrete under direct tensile loading, and also to insestigate the mechanism fiber reinforcement in order to improve the possible applications of steel-fiber reinforced concrete. In this study the major variables of experimental investigation were fiber conntents, and the lengths and diameters of fibers. The major results obtained are summarized as follows : 1. The strength, elastic modulus and energy absorption capability of steel-fiber reinforced concrete under direct tensile loading were improved as increasing of fiber contents. 2. The direct tensile strength of steel-fiber reinforced concrete was not influenced by the lengths of fiber, but was decreased as increasing of fiber diameters. 3. The direct tensile strength of steel-fiber reinforced concrete was not influenced by the fiber aspect-ratio, but this was because the fiber contents were below the critical value of fiber content. 4. The correlation of direct tensile strength and combined parameter, Vf l/d, was not good. 5. Mutiple cracking and post-crack resistance were investigated at stress-strain curves in direct tensile test. 6. The effect of fiber reinforcement can be influenced by fiber orientation and the bond strength between fiber and matrix. 7. The improvement of mechanical properties of steel-fiber reinforced concrete under direct tensile loading can be theoretically explained by the concept of composite materials.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.86-94
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• 2022

Replacement of FRP rod as steel reinforcement has been attracted significantly to prevent the degradation of the concrete structure due to corrosion. So, the technology development to extend the structure's service life by improving FRP properties has been proceeded worldwide. Accordingly, it is necessary to develop Korea's CFRP rod and CFRP grid, including the manufacturing techniques to improve the properties of high-strength and high-stiffness. Moreover, the research should be conducted to evaluate the structural behavior of the beams using the CFRP rod or grid. This study investigates the flexural and shear behavior of reinforced concrete beam using demonstrated CFRP rod as reinforcement according to the reinforcement ratio and shear span to depth ratio. From the results, when the reinforcement ratio is out of a specific range, it is seemed that the effect on performance improvement of the beam using CFRP rod is cancelled or not significant. Meanwhile, when the CFRP rod was used as reinforcement, the possibility of shear failure occurred, even steel stirrups were installed in the beam with CFRP rod as tensile reinforcement according to the Korean Design Standard. Therefore, when the CFRP rod is used as tensile reinforcement in a beam, it should be prepared that a specific limitation of reinforcement ratio and an investigation against shear failure. Also, the ductility of the beam using the CFRP rod is determined by the deformation energy evaluation method. So, the ductility should be investigated by applying the deformation energy evaluation method that reflects the structural behavior of the beam.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.279-282
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• 2005

Experimental study is performed to investigate the variation of shear strength of reinforced concrete beams according to design parameters. The major parameters are loading condition, shear span-to-depth ratio, ratio of tensile longitudinal reinforcement, prestress and boundary rigidity.14 reinforced concrete beams without web reinforcement are tested under monotonic downward loading. The shear strength of the tested specimens were compared with the prediction by design code and Choi's method.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.277-287
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• 2017

This paper describes the specifications on balanced steel ratio and maximum reinforcement for the design of RC flexural members by the Korean Highway Bridge Design Code based on limit states design. The Korean Highway Bridge Design Code (Limit States Design) is not provide for the balanced steel ratio specification for the calculation of required steel area of RC flexural members design. The maximum steel area limited the depth of the neutral axis at the ultimate limit states after redistribution of the moment, and also recommended the maximum steel area should not exceed 4 percent of the cross sectional area. However, from the maximum neutral axis depth provisions should increase the cross section is calculated to be less the maximum reinforcement area, and according to the 4% of the cross sectional area of the concrete, the tensile strain of the reinforcement is calculated to be greater than double the yielding strain, so can not guarantee a ductile behavior. This study developed a balanced reinforcement ratio that is basis for the required reinforcement calculation for tension-controlled RC flexural members design in the ultimate limit states verification provisons and material properties and applied the ultimate strain of the concrete compressive strength with a simple formular to be applied to design practice induced. And assumed the minimum allowable tensile strain of reinforcement double the yielding strain, and applying correction coefficient up to the ratio of maximum neutral axis depth, proposed maximum steel ratio that can be applied irrespective of the reinforcement yield strength and concrete compressive strength.