• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.415-418
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• 1999

This paper presents a study in the ductility of reinforced concrete beam-column-slab joints Three assemblies were designed 2/3 scale (f'c=240kg/$\textrm{cm}^2$, f'c=700kg/$\textrm{cm}^2$) and tested to investigate seismic behavior. From the test results, 1) flexural cracks emerge to inside of beam deeply for high strength concrete member, 2) the high-strength specimens degraded in stiffness and strength, and unstable hysteretic behaviors were observed, owing to the brittleness of high-strength concrete beyond its range. 3) The confinement provided by the additional hoops to the column bar is probably the main reason for this improvement in behavior.

• Computers and Concrete
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• v.19 no.1
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• pp.41-49
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• 2017

The use of external carbon-fiber-reinforced polymer (CFRP) wraps is one of the most effective techniques existing for the confinement of the circular concrete columns. Currently, several researches have been made to develop models for predicting the behavior of this type of confinement. The disadvantage of the most models, is to not take into account the contribution of the transverse steel reinforcements (TSR) effect, However, very limited models have been recently developed that considers this combined effect and gives less accurate results. This paper presents the development of a new model for the axial behavior of circular concrete columns confined by combining external CFRP warps-and-internal TSR (hoops or spirals) based on the existing experimental data. The comparison between the proposed model and the experimental results showed good agreement comparing to the several existing models. Moreover, the expressions of estimating the ultimate strength and the corresponding strain are simple and precise, which make it easy to use in the design applications.

• Architectural research
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• v.17 no.1
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• pp.41-48
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• 2015

Early investigations focused mainly on manipulating the confinement effect to develop a reinforced concrete column with lateral hoops. Based on this legacy model, Li's model incorporated the additional confinement effect of a steel jacket. However, recent experiments on plain concrete cylinders with steel jackets revealed relatively large discrepancies in the estimates of strength enhancement and the post-peak behavior. Here, we describe a modified constitutive law for confined concrete with an unbonded external steel jacket in terms of three regions for the loading stage. We used a two-phase heterogeneous concrete model to simulate the uniaxial compression test of a $150mm{\times}300mm$ concrete cylinder with three thicknesses of steel jackets: 1.0 mm, 1.5 mm, and 2.0 mm. The proposed constitutive model was verified by a series of finite element analyses using a finite element program. The damaged plasticity model and extended Drucker-Prager model were applied and compared in terms of the level of pressure sensitivity for confinement in 3D. The proposed model yielded results that were in close agreement with the experimental results.

• Computers and Concrete
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• v.5 no.6
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• pp.525-544
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• 2008

In this research, the self-centering effect in precast and prestressed reinforced concrete structures was investigated experimentally. The reinforced concrete beams and columns were precast and connected by post-tensioning tendons passing through the center of the beams as well as the panel zone of the connections. Three beam-to-interior-column connections were constructed to investigate parameters such as beam to column interfaces (steel on steel or plastic on plastic), energy dissipating devices (unbonded buckling restrained steel bars or steel angles) and the spacing of hoops in the panel zone. In addition to the self-centering effect, the shear strength in the panel zone of interior column connections was experimentally and theoretically evaluated, since the panel zone designed by current code provisions may not be conservative enough to resist the panel shear increased by the post-tensioning force.

• Journal of the Korean Home Economics Association
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• v.19 no.3
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• pp.1-9
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• 1981

The object of this study lies in reviewing of the western costume history in the light of the negative regulations concerning costumes and adornments. Readings related with the subject lead to the following findings; 1. the principal purpose of the sumptuary laws has relationship with the social stratification of the feudalism and the frequency of their occurrence is related with the formation of feudal system, its decline, the appearance of imperial regimes and the start of civil revolutions. 2. Sumptuary regulations spread westward with the flow of civilization, eg., in the sequence of Italy, swiss, France, Britain and new world. 3. Sumptuary laws are also found in abundance in the english colonies of America, and their object seems to be rather of the moral concern than class distinction of economical restriction.4. The reviewed sumptuary regulations are concerned with : A. Material gold or silver clothes, silks, ermine, marten or miniver furs, velvets, laces and embroies. B. Colors-Purple, scarlet and red. Other colors do not show consistent pattern of color-status symbol; C. Form-Length and width of headdresses, shoes, collars, trains or hoops. E. numbers of dresses allowed to be worn.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.931-936
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• 2003

Lap splices were located in the plastic hinge region of most bridge piers that were constructed before the adoption of the seismic design provision of Korea Highway Design Specification on 1992. Lap splicing is also permitted if hoops or spiral reinforcement are provided over the lap length in the current seismic design provision. But sudden brittle failure of lap splices may occur under inelastic cyclic loading. The purpose of this study is the analytical prediction of nonlinear hysteretic behavior and ductility capacity of reinforced concrete bridge piers with lap splices under cyclic loading. For this purpose, a nonlinear analysis program, RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology) is used. Lap spliced bar element is developed to predict behaviors of lap spliced bar. Maximum bar stress and slip of lap spliced bar is considered.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1993.04a
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• pp.87-94
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• 1993

The study summarized in this paper is concerned with the buckling of a longitudinal bar in reinforced concrete members by numerical analysis method. The objectives of this study are to investigate the stress transfer mechanism between concrete and reinforcment and to propose a modeling equation. The result gives an acceptable agreement between the proposed modeling equation and the computer package as follows: (1) the proposed equation is a possible prediction of the strain softening of concrete and reinforcement buckling. (2) the buckling of longitudinal bars is mainly influenced by the spacing of hoops and the location of the bar.

• 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.

• Computers and Concrete
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• v.7 no.1
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• pp.1-16
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• 2010

A simplified method, developed from the softened strut-and-tie model, for determining the mid-span deflection of deep beams at ultimate state is proposed. The mid-span deflection and shear strength predictions of the proposed model are compared with the experimental data collected from 70 simply supported reinforced concrete deep beams, loaded with concentrated loads located at a distance a from an end reaction. The comparison shows that the proposed model can accurately predict the mid-span deflection and shear strength of deep beams with different shear span-to-depth ratios, different concrete strengths, and different horizontal and vertical hoops.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.743-754
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• 1997

A three-dimensional constitutive modeling for reinforced concrete is presented for finite element nonlinear analysis of reinforced concrete. The targets of interest to the authors are columns confined by lateral steel hoops, RC thin shells subjected to combined in-plane and out-of-plane actions and massive structures of three-dimensional (3D) extent in shear. The elasto-plastic and continuum fracture law is applied to pre-cracked solid concrete. For post cracking formulation, fixed multi-directional smeared crack model is adopted for RC domains of 3D geometry subjected to monotonic and reversed cyclic actions. The authors propose a new scheme of decomposing stress strain fields into sub-planes on which 2D constitutive laws can be applied. The proposed model for 3D reinforced concrete is experimentally verified in both member and structural levels under cyclic actions.