• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.704-707
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• 2004

The structure should be designed to be safe to any direction of earthquake input. However, the reference axes whereby the structure is analyzed and designed against earthquake may influence the design member forces. This study is concerned with the effect of the choice of the reference axes on the seismic design member forces. The analytical results on member forces using the principal axes suggested by Wilson and the global axes generally adopted in design offices show that the values of member forces by the principal axes be about $15\%$ smaller than those by the global axes in the example structure.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.121-126
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• 2000

The attaching method of different types of structure and explanation of stress transfer mechanism are at important issue as beam having definitive factor such as the anchorage of RC main bar, the stress transfer of anchorage-end S member, RC member-anchorage, anchorage-end S member in the composite beam of S and RC member. In this study, the structural properties of composite beam according to attaching method of main bar about end RC-middle S beam were investigated in order to use them as fundamental data for the development of composite structure member. Throughout a series of study, it was shown that the proof stress of main bar - flange welding specimen is the highest and there is no difference between the deformation-properties according to attaching method of main bar.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.355-360
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• 1999

Polymer cement is made by the modifying ordinary cement concrete with polymer additive. Until now polymer cement concrete is not used for the structural member, but it is growing to be considered as developing uses such as a waterproof of roof slab, the structural member for protecting corrosion, and a road pavement. The plymer cement concrete, being used for those uses, is superior to the cement concrete against the inorganic, organic acid, salt of acetic acid and organic solvents generally. In this paper, the polymer cement concrete was made by the ratio of 1:1 of sands and tailing in fine aggregate in order to solve the environmental pollution which causes the social problem by the tailing, It was measured for the compressive strength, flexural strength, and chemicals resistance was tested by dealing with 10% HCI, 20% NaOH and 10% NaCl aqueous solution.

• Magazine of the Korea Concrete Institute
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• v.3 no.4
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• pp.97-106
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• 1991

The object of this study is to propose the Flexural moment-curvature relationship based on the bond property between concrete and steel for noncracking zone, to evaluate the flexural displacement of reinforced concrete member. The bond-slip relationship and the strain hardening effect of steel were taken into consideration in order to evaluate the spacing of the cracks and the curvature distribution. Calculated curvature distribution along the longitudinal axis was transformed into equivalent curvature distribution. The flexural displacement was calculated by means of double integrals of the equivalent curvature. Furthermore, 34 beams were tested in order to verify the proposed procedure Calculated values agreed well with the experimental data, and so it is pointed out that proposed method is widely acceptable for the practical evaluation of flexural displacement of reinforced concrete member.

• Journal of the Korea Concrete Institute
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• v.11 no.5
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• pp.79-88
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• 1999

The purpose of this paper is to develop a mathematical expression for computing crack angles based on reinforcement volumes in the longitudinal and transverse directions, member end-fixity and length-to-width aspect ratio. For this a reinforced concrete beam-column element is assumed to possess a series of potential crack planes represented by a number of differential truss elements. Depending on the boundary condition, a constant angle truss or a variable angle truss is employed to model the cracked structural concrete member. The truss models are then analyzed using the virtual work method of analysis to relate forces and deformations. Rigorous and simplified solution schemes are presented. An equation to estimate the theoretical crack angle is derived by considering the energy minimization on the virtual work done over both the shear and flexural components the energy minimization on the virtual work done over both the shear and flexural components of truss models. The crack angle in this study is defined as the steepest one among fan-shaped angles measured from the longitudinal axis of the member to the diagonal crack. The theoretical crack angle predictions are validated against experimentally observed crack angle reported by previous researchers in the literature. Good agreement between theory and experiment is obtained.

• International Journal of Concrete Structures and Materials
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• v.5 no.2
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• pp.77-85
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• 2011

The use of headed bars as opposed to standard 90- or 180-degree hooked bars in beam ends, beam-column joints or other steel congested areas for anchorage and bond has become more favorable due to the fact that steel congestion is often created by large bend diameters or crossties. This research mainly focuses on evaluating the code provisions regarding the use of headed bars. Nine simply supported rectangular concrete beams with headed longitudinal reinforcement were tested under a four-point monotonic loading system. The design clear spacing, which varies from 1.5 to 4.25 times the bar diameter, was the only parameter for the experimental investigation. The test results showed that the closely-spaced headed bars were capable of developing to full yield strength without any severe brittle concrete breakout cone or pullout failure. Bond along the bar was not sufficient due to the early loss of concrete integrity. However, the headed bars were effective for anchorage with no excessive moment capacity reduction. This implies that the clear spacing of about 2 times the bar diameter for headed bars may be reasonable to ensure the development of specified yield strength of headed bars and corresponding member design strength.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.207-214
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• 1997

This study was performed to verify the effect of axial force due to restraint on the mechanical behavior and the average crack spacing of the reinforced concrett. ilexural menlbers. For. this purpose, the flexural sttvngt.h and rigidity werc experimentally investigated undcl. axially rcstmined and unr.est.rainrd conditions. Furthermore , the average crack spacing was also checkcd for the axilly restrained contlit.ion. Thc test results showd that the flexual strength and rigidity of t,he restrained beam were higher. than those of the unrestrained beam. The major. factors affecting on the average crack spacing were steeel stress, axial force, cicumference of reinforcing bar and effective tension arm of concrete. However. the concrete compressive strength was minor effect. Including thesc factors, a prediction equation for the average crack spacing of the restrained member was proposed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.2
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• pp.149-158
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• 2011

Utilization of the fiber reinforced polymer (FRP) material has been increased as an alternative in a bid to supplement the problems with general construction materials such as long-term problems corrosion, etc. However, there are still many problems in using a linear-shaped FRP material for a tunnel lining structure which has arch-shape in general. In this study, the loading tests for the FRP-concrete composite member was carried out to evaluate their applicability as a tunnel reinforcement material, which are based on the results from preliminary numerical studies for identifying the behavioral characteristics of FRP-concrete composite member. Moreover, numerical analysis under the same condition as applied in the loading tests was again conducted for analysis of mechanical behavior of the composite member. As a result of the load test and numerical analysis, it appears that the FRP-concrete composite member is greatly subject to shear movement caused by bending tension acting on the interface between two constituent members.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.29-36
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• 1987

In most of the structural members with initial cracks, the strength tends to decrease as the member size increases. This phenomenon is known as size effect. Among the structural materials of glass, metal or concrete, etc., concrete represents the size effect even without initial crack. According to the previous size effect law, the concrete member of very large size can resist little stress. Actually, however, even the large size member can resist some stress if there is no initial notch. This means that the fracture mechanism of very small or very large size member follows strength criterion, but the medium size member follows non-linear fracture mechanics (NLFM). In this study, the empirical models which are derived based on nonlinear fracture mechanics are proposed according to the regression analysis with the existing test data of large size specimens for uni-axial compression test, splitting tensile test and shear test of reinforced concrete beams.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1185-1190
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• 2011

In designing cut and cover tunnels, load combination applied Korea seismic design code of urban transit and its sections applied Korea concrete code 2003. However, by revision of Korea concrete code in 2007, engineers have been experiencing difficulties in their work. In this study, application of Korea concrete code 2007 for designing is reviewed by comparing load combination of related codes and member force.