• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.303-306
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• 1999

For the purpose of Military means, explosion proof concrete, which protect the structures from the damage due to the explosion of bomb and maintain its shape, is required to develop. Therefore, in this paper, mechanical and explosionproof properties of concrete are tested under various steel fiber contents and member size. According to the experimental results, compressive, tensile and flexural strength go up with the increase of fiber contents. Energy bearing capacities is higher with the increase of fiber contents. Especially, it is confirmed that slurry infiltrated fiber concrete (SIFCON) gains in high strength and has high energy bearing capacities. SIFCON is expected to apply in the construction of explosion proof structures.

• Architectural research
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• v.1 no.1
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• pp.55-61
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• 1999

In reinforced concrete design, structural member sizes and amount of reinforcing steel areas are usually selected based on the structural designers' experience. Most existing charts provided for the design of reinforced concrete structural members were developed mainly based on force equilibrium conditions and some serviceability criteria. Sections selected from these charts may not result in an economic solution in terms of material costs as well as construction costs. Practical design aids are developed and suggested in this study for the economical design of reinforced concrete beam under flexural loading. With the beam width fixed, the depth of a beam, positive steel areas and negative steel areas are found from Khun-Tucker necessary conditions with Lagrangian multipliers to minimize the sectional cost of a beam. The developed design aids might be useful in selecting optimum reinforced concrete beam sections. Theoretical derivations and use of the developed design aids are described in this paper.

• Journal of the Korea Concrete Institute
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• v.28 no.1
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• pp.3-11
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• 2016

The concern about hollow core PC slab has been increased to improve the workability during a construction of building by reducing self weight of structural members. In this manner, recently, TRS (Tripple Ribs Slab) was developed as a new type of half PC slab system. TRS member consists of the triple webs and the bottom flange prestressed by strands. The slab system is completed by casting of topping concrete on the TRS after filling styrofoam between the webs. This paper, presents a flexural experiment to investigate the flexural capacity of the TRS. Five full scale TRS members were made and tested under simple support condition to be failed by flexure and their strength was evaluated by code equations; the variables in the test are the depth and the presence of topping or raised spot formed when slip-forming. In addition, a nonlinear sectional analysis was performed for the specimens and the result was compared with the test results. From the study, it was found that the TRS has enough flexural strength and ductility to resist the design loads and its strength can be suitably predicted by using code equations. The raised spot did not affect the strength so that the spot need not to be removed by doing additional work. For the more accurate prediction of TRS's flexural behavior by using nonlinear sectional analysis, it is recommended to consider the concrete's brittle property due to slip-forming process in the modeling.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.249-256
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• 2008

The durability of marine concrete structure is severely degraded by corrosion due to penetration and diffusion of chloride. So, many researches have been performed to improve the durability in marine concrete structure. In this study, the concrete members mixed with the mineral admixtures(SF and BFS), the epoxy-coated steel, and corrosion inhibitors are prepared, and four-point bending test of specimens are performed to investigate the flexural behaviors and the applicability for marine concrete structure. From the test results, the mineral admixtures and inhibitors are useful for safety against the initial cracking and the bending resistance in specimens. When the durable material is used in specimen, the tensile stress of reinforcing rod was less variable in same bending span length, and the durable member showed a stable behavior. And it is evaluated that the crack spacing is not larger in specimen used the durable material.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.519-524
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• 1998

The current study is a part of series of research about the evaluation method of the unbonded tendon stress in prestressed concrete member at flexural failure. As the experimental study, a test program with 14 beams and slabs was planed to identify the contribution of each important variable. The variables are (1) the effective prestress, (2) the concrete strength, (3) the amount of tendons (4) the amount of bonded reinforcements, (5) the loading type, (6) the span/depth ratio. It was found that the tendon stress increment decreases as the effective prestress increases. Also, the contributions of concrete strength, amount of tendons, bonded reinforcements, and loading type were observed to affect on tendon stresses. However, the tendon stress increments were minimal at high values of span/depth in contrast with the ACI Code.

• Structural Engineering and Mechanics
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• v.28 no.5
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• pp.587-601
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• 2008

In this study, a numerical procedure based on the finite element method for materially and geometrically nonlinear analysis of reinforced and prestressed concrete slender columns with arbitrary section subjected to combined biaxial bending and axial load is developed. In order to overcome the low computer efficiency of the conventional section integration method in which the reinforced concrete section is divided into a large number of small areas, an efficient section integration method is used to determine the section tangent stiffness. In this method, the arbitrary shaped cross section is divided into several concrete trapezoids according to boundary vertices, and the contribution of each trapezoid to section stiffness is determined by integrating directly the trapezoid. The space frame flexural theory is utilized to derive the element tangent stiffness matrix. The nonlinear full-range member response is traced by an updated normal plane arc-length solution method. The analytical results agree well with the experimental ones.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.3
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• pp.129-136
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• 2000

In the side of military purpose, the explosion proof concrete, which contributes to protect the military facilities from damages due to the explosion of bomb and to maintain their shapes, is required to develop, Therefore. in this paper, mechanical and explosion-proof properties of concrete are tested under various steel fiber contents and member size. According to the experimental results, compressive, tensile and flexural strength gain higher levels with an increase in fiber contents. It shows that energy bearing capacities are higher with an increase in fiber contents. Especially. it is confirmed that slurry infiltrated fiber concrete(SIFCON) gains high strength and has high energy bearing capacities. SIFCON is expected to be applied in the construction of explosion proof structures.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.139-146
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• 2002

A analysis of crack behavior in RC member was performed by nonlinear finite element method. Two crack models were used in F.E.M.(finite element method): one was FCM (the fixed crack model) and the other was RCM (the rotated crack model). Based on parametric study, the ratio of shear steel, strength of concrete, and a/d(shear span/effective depth) were compared with test results of references. According to the test results, when the member behavior was affected by the shear or diagonal tension, RCM was reasonable. However, when the behavior was affected by the flexibility, FCM was more appropriate. In addition, each crack model behavior for the change of shear steel ratio, the increase of strain energy was constant in FCM, but it was different in RCM because of diagonal crack distribution and crack width. Since the strength of concrete is affected not only by shear but also by flexural strength, each crack model behavior yields similar results.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.892-899
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• 2002

Among the methods for enhancement of load-carrying capacity on flexural concrete member, recently, a concept is being investigated which replaces the steel in a conventional reinforced concrete member with a fiber reinforced polymer(FRP) shell. This study focuses on modeling of the structural behavior of concrete surrounded with FRP shells in flexural bending members. A numerical model of fiber cross-sectional analysis is proposed to predict the stress and deformation state of the FRP shell and concrete. The stress-strain relationship of concrete confined by a FRP shell is formulated to be based on the constitutive law of concrete in multi-axial compressive stress state, in assuming that the compression response is dependent on the radial expansion of the concrete. To describe the FRP shell behavior, equivalent orthotropic properties of in-plane behavior from classical lamination theory are used. The present model is validated to compare with the experiments of 4-point bending tests of FRP shell concrete beam, and has well predicted the moment-curvature relationships of the members, axial and hoop strains in the section, and the enhancement of confinement effect in concrete surrounded by FRP shell.