• Proceedings of the KSME Conference
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• 2000.11a
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• pp.177-184
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• 2000

In this work, some inaccuracies and limitation of prior indentation theory, which is based on the deformation theory of plasticity and experimental observations, are first investigated. Then effects of major material properties on the configuration of indentation load-deflection curve are examined via incremental plasticity theory based finite element analyses. It is confirmed that subindenter deformation and stress-strain distribution from the deformation theory of plasticity are quite dissimilar to those from incremental theory of plasticity. We finally suggest the optimal data acquisition location, where the strain gradient is the least and the effect of friction is negligible. This data acquisition point increases the strain range by a factor of five.

• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.5
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• pp.29-37
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• 2008

Stress-strain relation and stress block parameters of polymer concrete flexural compression members were experimentally investigated. For these purposes, a series of C-shaped polymer concrete specimens subjected to axial compressive load was tested. Based on the test results, we proposed an equation by which the stress-strain relation of polymer concrete can be predicted. In this model, we took account the slope of descending branch beyond the peak stress point of single curve. The proposed equation was numerically integrated to compute the rectangular stress block parameters. Computed ${\beta}_1$ was greater than the values prescribed in ACI 318 Code for cement concrete, and $\gamma$ was about 0.85 that is similar to the value regulated in the ACI.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.1
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• pp.53-64
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• 2000

Strain gage method is investigated to evaluate the mode I stress intensity factor. Two types of specimens for CT and three point bend specimen are used. Sharp notch of specimens is manufactured by wiring discharge machining. Strain gages signal from the crack tip region are used to calculate stress intensity factors. The results are compared with those of the ASTM E399 method and finite element analysis. The present experimental results coincide well with the data obtained from finite element analysis. Attached position of strain gage should be seriously considered during the application of this method.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.685-692
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• 2004

A stochastic approach has been presented for superplastic deformation of Ti-6Al-4V alloy, and probability functions are used to model the heterogeneous phase distributions. The experimentally observed spatial correlation functions are developed, and microstructural evolutions together with superplastic deformation behavior have been investigated by means of the two-point and three-point probability functions. The results have shown that the probability varies approximately linearly with separation distance, and deformation enhanced probability changes during the process. The stress-strain behavior with the evolutions of probability function can be correctly predicted by the model. The finite element implementation using Monte Carlo simulation associated with reconstructed microstructures shows that better agreement with experimental data of failure strain on the test specimen.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.547-552
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• 1998

Lateral pressure by circular reinforcement greatly enhances the maximum strength and ductility of spiral columns. The lateral confinement effects will be improves ductility of high-strength concrete. The major purpose of this paper is to study on the improvements of maximum strength and strain at that point of spiral concrete columns subject to axial loads. For this purpose, this study collected the other analytical results and the experimental data that has been performed by a lot of worldwide researchers and also analyzed it statistically. As the result, the theoretical equation for predict maximum strength and strain at that point was proposed. It is based on calculation of lateral confinement pressure generated by circular reinforcement, and the resulting improvements in strength and ductility of confined concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.405-410
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• 2002

This paper deals with the flexural behavior of RC hems strengthened with CFRP plate and the estimation on anchorage length of CFRP Plate. Experimental variables included concrete strength, reinforcement ratio, cover thickness of concrete and length ratio of CFRP plate for a pure span. A failure load, failure mode, deflection and strain response at different distances from a cut-off point of CFRP plate were observed and anchorage length was determined through strain distribution of CFRP plate. Herein, anchorage length is defined the length between CFRP plate end and the beginning point of full composite behavior. Also, the anchorage length observed from the experiment was compared with Nguyen's equation and BS specification.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.206-211
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• 2004

This paper deals with the flexural strengthening of reinforced concrete beams by means of thin fiber reinforced plastic(FRP) laminas. This study focuses on modeling of structural of concrete bonded FRP laminate in flexural bending members. Used computational equation is derived by relation of stress and strain. The section analysis is based on experimental observations of a linear strain distribution in the cross section until failure, and a multi-linear moment-deflection curve that is divided into four regions, each terminated by a similarly numbered point. The load-deflection relationship in each region is assumed to be linear. The present model is validated to compare wit the experiment of 4-point bending tests of R/C rectangular beams strengthened with CFRP laminates, and has well predicted the moment-displacement relationships of members.

• Computers and Concrete
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• v.4 no.2
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• pp.83-100
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• 2007

Applying a direct formulation for the enrichment of the displacement field an extended finite element (XFEM) scheme for modeling of cohesive crack growth is developed. Only elements cut by the crack is enriched and the scheme fits within the framework of standard FEM code. The scheme is implemented for the 3-node constant strain triangle (CST) and the 6-node linear strain triangle (LST). Modeling of standard concrete test cases such as fracture in the notched three point beam bending test (TPBT) and in the four point shear beam test (FPSB) illustrates the performance. The XFEM results show good agreement with results obtained by applying standard interface elements in FEM and with experimental results. In conjunction with criteria for crack growth local versus nonlocal computation of the crack growth direction is discussed.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.2
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• pp.84-93
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• 2000

Computer simulations of the mechanical behavior of 3 point bend specimens with a quarter notch under impact load are performed. This validity is found to be identified by the experimental proof. The cases with various loading rates applied at the side of the specimen are considered. An elastoplastic von Mises material model is chosen. Gap opening displacement, reaction force, crack tip opening displacement and strain rate are also compared with rate dependent material(visco-plastic material). The stability during various dynamic load can be seen by using the simulation of this study. These differences of the cases with various loading rates are also investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.609-614
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• 1998

Lateral pressure by tied reinforcement greatly enhances the maximum strength and ductility of columns under concentric loading. The lateral confinement effects will be improves ductility of high-strength concrete. The major purpose of this paper is to study on the improvements of maximum strength and strain at the point of tied high-strength concrete columns subject to axial loads. For this purpose, this study collected the other analytical results and the experimental data that has been performed by a lot of worldwide researchers and also analyzed it statistically. As the result, the theoretical equation for predict maximum strength and strain at the point was proposed. It is based on calculation of lateral confinement pressure generate from tensile that develop in transverse reinforcement.