• 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.

• Journal of Korean Association for Spatial Structures
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• v.18 no.4
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• pp.123-130
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• 2018

U-flanged truss beam is composed of u-shaped upper steel flange, lower steel plate of 8mm or more thickness, and connecting lattice bars welded on the upper and lower sides. The hybrid beam with U-flanged steel truss is made in the construction site through pouring the concrete, and designated as U-flanged truss hybrid beam. In this study the structural experiments on the 4 hybrid beams with the proposed basic shapes were performed, and the flexural capacities from the tests were compared with those from the theoretical approach. The failure modes of each specimen were quite similar. The peak load was reached with the ductile behavior after yielding, and the failure occurred through the concrete crushing. The considerable increasement of deformation was observed up to the concrete crushing. The composite action of concrete and steel member was considered to be reliable from the behavior of specimens. The flexural strength of hybrid beam has been evaluated exactly using the calculation method applied in the boubly reinforced concrete beam. The placement of additional rebars in the bottom instead of upper side is proposed for the efficient design of U-flanged truss hybrid beam.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.313-316
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• 2006

Externally prestressed structures have many advantages such as easy prestressing control and visible maintenance. Flexural strength of externally prestressed concrete members can be calculated by analysis of internal indeterminacy, which is different from internally prestressed concrete members. However, it needs nonlinear analysis considering member stiffness at strength limit state. Thus most of design codes proposed approximate methods which are empirical, based on test results. To reduce difference between accurate analysis and approximate design methods, many experiments and studies are continued. Since most of the experiments are single span beams. In order to adapt of continuous beam it needs further investigation for the continuous beam. In this study, we carried out externally prestressed 2-span concrete beam test to find out the flexural behavior and strength of externally prestressed concrete members.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.463-468
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• 2002

For the Externally bonded FRP systems, flexural design method is studied focusing on the reinforcement layer of the carbon fiber sheets. As the FRP layer is added, strengthening rate increases, but not proportionally as the FRP layer increases. This is reflected in the design formula appropriately by the bond cofficients from the added layers. As the number of FRP layer increases, the stress reinforcement and FRP sheet decreases, and it generally corresponds to the decrease rate of member flexural strength. This phenomenon is appearing indentically in a design formula and experimental result. The rate of $M_{test}$ and $M_n$ is 1.19 and it is estimated as safety factor which is the reduction factor, ${\psi}_f = 0.85$.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.897-902
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• 2001

Recently, structure performance is maximized by using high strength concrete. In design of structure, concrete need combination with reinforcement, but use of common strength reinforcement make member complex bar placement, so high strength concrete members require increased strength reinforcement. If common strength reinforcement replaced by equal tension area of high strength reinforcement, reinforcement ratio increase and brittle failure of member may occur by material change. So, adequate upper limit of strength ratio is required to affirm ductile behavior in application of high strength reinforcement. In this study, ductility behavior was analysed by factor of reinforcement ratio, strength of concrete and reinforcement. The result indicate that ductile failure is shown under 0.35 $\rho_{b}$ in any reinforcement strength of same section and high strength concrete of 800kg/$cm^{2}$ used commonly is compatible with reinforcement of 5500kg/$cm^{2}$.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.733-738
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• 2000

This paper was aimed to evaluate the structural performance of flexural members repaired by polymer cement and epoxy mortar at soffit. Main test variables were repair materials, ratio of reinforcement and additional reinforcing bars. Test results shows that the repaired beams could change flexural capacity by materials and additional reinforcing bars. In polymer cement, the section repaired can carry same load, cracking moment and the flexural stiffness of the monolithic beams with same size. In epoxy mortar, all data were greater than the shotcrete. However, note that epoxy mortar may conduct member into brittle failure mode.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.129-132
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• 2006

It is generally reported that most of RC beams strengthened with simply bonded FRP composite is failed by FRP debonding. Also, the flexural performance of RC member strengthened with FRP composite can be calculated using the effective strain of FRP. The effective strain as a result of the debonding failure depends on many variables, such as FRP stiffness including the thickness($t_f$) and modulus of elasticity($E_f$), the amount of FRP but the FRP stiffness is reportedly the most influential. The purpose of this paper, therefore, is to examine effects of FRP stiffness on the flexural strengthening of RC beams. 4 different stiffness of CFRP composite including CFRP sheet and laminae were selected. From the tests, it was found that the flexural performance of RC beams strengthened with CFRP composite can be calculated based on the effective strain of the CFRP composite and the effective strain is inversely proportional to the CFRP stiffness.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.16-25
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• 2018

Concrete is a suitable construction material for long-term structure, however, it is needed to understand the calcium leaching damage caused by exposure to underground pure water for a long time. In this paper, it is experimentally investigated that the characteristics of flexural behavior in RC member damaged by calcium leaching degradation. From the test results, when calcium leaching is happened, yielding load and flexural rigidity is reduced, neutral axis depth and displacement is increased. That is, calcium leaching degradation adversely affects RC member performance. And, when the mineral admixture is used in the calcium leaching environment, it is considered that the optimal replacement ratio should be prepared according to the type of mineral admixture.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.563-570
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• 2016

The composited structural member in which two or more materials having different stress-strain relationships (steel & concrete) has increased greatly in recent years. This paper presents the experimental results of flexural capacity of the composited H-Pile subjected to bending moment. Eight composited beams were tested under direct loading condition using the frame tester. Based on the experimental results it is noted that flexural capacity of composited H-Pile increased about 20~30% and ductility ratio significantly increased. Limit state analysis of the specimens was conducted and the result shows that flexural strength by limit state analysis is conservative.

• Earthquakes and Structures
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• v.5 no.5
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• pp.527-552
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• 2013

Development of flexural yielding and large rotation ductilities in the plastic hinge zones of frame members is synonymous with the spread of bar reinforcement yielding into the supporting anchorage. Yield penetration where it occurs, destroys interfacial bond between bar and concrete and reduces the strain development capacity of the reinforcement. This affects the plastic rotation capacity of the member by increasing the contribution of bar pullout. A side effect is increased strains in the compression zone within the plastic hinge region, which may be critical in displacement-based detailing procedures that are linked to concrete strains (e.g. in structural walls). To quantify the effects of yield penetration from first principles, closed form solutions of the field equations of bond over the anchorage are derived, considering bond plastification, cover debonding after bar yielding and spread of inelasticity in the anchorage. Strain development capacity is shown to be a totally different entity from stress development capacity and, in the framework of performance based design, bar slip and the length of debonding are calculated as functions of the bar strain at the loaded-end, to be used in calculations of pullout rotation at monolithic member connections. Analytical results are explored parametrically to lead to design charts for practical use of the paper's findings but also to identify the implications of the phenomena studied on the detailing requirements in the plastic hinge regions of flexural members including post-earthquake retrofits.