• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.1 s.173
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• pp.250-258
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• 2000

The reinforcing effects of ductile short-fiber reinforced brittle matrix composites are studied by, measuring flexural strength, fracture toughness and impact energy as functions of fiber volume fraction and length. The parameters of fracture mechanics, K and J are applied to assess fracture toughness and bridging stress. It is found that fracture toughness is greatly, influenced by the bridging stress ill which fiber pull-out is occur. For the reinforcing effects as functions of fiber volume fraction($V_f$ = 1, 2, 3 %) and length(L = 3, 6. 10cm), the flexural strength is maximum at $V_f$ = 1% and both fracture toughness.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.617-620
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• 1999

The purpose of this study is to find the influence of interface and confinement on bond between reinforcing steel and concrete subjected to monotonic and cyclic loading. The key variables for the experimental program include rib height, rib spacing for reinforcing bars and confinement. From the results obtained in this study, the following main observations can be made for the bond properties. Bond strength increases when confinement increases under monotonic and cyclic loading. Bond stiffness and strength drop remarkably after the maximum bond strength. Both bond stiffness and strength also drop at a constant slip when the number of cyclic loading increase. The bond resistance subjected to cyclic loading decreases significantly for reinforcing bars with low rib height.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.517-520
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• 1999

In this study, the problem of strengthening of reinforced concrete (RC) columns by a central steel section with minimum amount is taken up. For this purpose, RC columns with central reinforcing elements such as a steel bar, a steel H section and a steel pipe were taken up. To certify the effect of this way of reinforcing, experimental study using specimens of RC columns of shear span ratio of 2.5 was carried out. The variables which are considered to affect the behavior of RC columns subjected to axial load and cyclic shear load are the magnitude of axial load, tie ratio and main bar ratio. As the results of this study, the effect of a central reinforcing element for making higher the earthquake resistant properties of RC columns were observed.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.653-660
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• 1998

Bond strength of reinforcing bar to high-performance concrete using belite cement is explored using beam end test specimen. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete covers. Specimen failed in the typical brittle bond failure splitting the concrete cover as the wedging action. The test results show that the specimens with belire cement concrete show higher bond strength than those with portland cement concrete. Bond strength of the top bar is less than bond strength of bottom bar, but the top bar factor satisfies the modification factor for top reinforcement. The results also show that the bond strength is function of the square root of concrete compressive strength and cover thickness. The recently developed high-strength and high-slump concrete with belite cement performs well in terms of bond strength to reinforcing steel.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.65-70
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• 1994

Reinforced concrete and prestressed concrete structures consist of different materials, namely concrete, reinforcing steel and/or prestressing steel. Reinforcing and prestressing steels can be considered homogeneous materials, and their properties are generally well defined. Howefer, concrete is a heterogeous materials, and it is difficult to define its properties accurately. Both concrete and steel exhibit various nonlinear materials properties. The stress-strain relationship of concrete is not only nonlinear, but it differs in compression and tension. And, tensile cracking is one of the most importnat factors which contribute to the nonlinear behavior of reinforced concrete structrures. In this strudy, the various stress-strain relationships of concrete and reinforcing steel in nonlinear analysis of RC and PC structures are examined.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.59-66
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• 2004

This study compared the reinforcing effect of sand by Geocell to those of newly devised Tirecell$^{\circledR}$ made by waste tires, tire mat by sidewalls of tires. Plate loading tests in a large chamber were conducted for different reinforcing materials at the same conditions of relative density, embedded depth of sand. The combination of Tirecell and sidewall gives the highest increase of bearing capacity and reduction of settlement. The Geocell with the same height of Tirecell gives similar reinforcement effect to the tire mat made by sidewalls.

• Journal of Korean Association for Spatial Structures
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• v.13 no.1
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• pp.105-112
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• 2013

An automation of standardized rebar shop drawing is necessary for easy application by improving workability, prompt preparation to field change request and easy revisions of shop drawing. Through investigating problem of current rebar shop drawing, we found that standardization of reinforcing detail, standardization of rebar expression and automation of rebar shop drawing program for the sake of designer is needed. We will investigate disagreement of reinforcing detail between building code and how worker build structure for standardization of reinforcing detail, demands of companies participated in rebar process for standardization of rebar expression and proper algorithm with selectable level of inputting data for automation of rebar shop drawing program for the sake of designer.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2002.05a
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• pp.97-102
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• 2002

The ability to pass between bars is one of the most important performance of self-compacting concrete or high-flowability concrete since it determines the final filling capacity which influences the strength and durability of hardened concrete in structure. Therefore it has been evaluated by many researchers using different kinds of testing apparatuses. The assessments of passing ability, however, differ largely according to the style, the dimension and the criteria in apparatuses, and the value obtained from one apparatus cannot be converted those of the others. There needs a rheological approach to the better understanding of the passing behavior of fresh concrete between reinforcing bars, where the flow velocity of concrete becomes slow and the blockade sometimes occurs due to the interference between aggregates and reinforcing bars. Experimental works were conducted to clarity the effects of the clearance between reinforcing bars, the volume of aggregate and the rheological properties of matrix on the behavior from the rheological point view and showed the rational mix proportioning of concrete.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.10a
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• pp.43-48
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• 2001

To overcome the disadvantages of conventional excavation technology, various trenchless (or excavation free, or no-dig) repair-reinforcement technologies have been developed and tried. But trenchless technologies so fat developed have some brawbacks such as high cost and inconvenience of operation. In this study, a repairing-reinforcing process for underground pipes with glass fiber fabric polymer composites using VARTM(Vacuum Assisted Resin Transfer Molding) has been developed. The developed process requires shorter operation time and lower cost with smaller and simpler operating equipments than those of the conventional trenchless technologies. For the reliable operation of the developed method, a simple method to apply pressure and vacuum to the reinforcement was devised and flexible mold technology was tried. Also, resin filling and cure status during RTM process were monitored with a commercial dielectrometry cure monitoring system, LACOMCURE. From the investigation, it has been found that the developed repairing-reinforcing technology with appropriate process variables and on-line cure monitoring has many advantages over conventional methods.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.141-148
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• 2005

When one opens the door of a microwave oven during operation, microwave might leak through the clearance of the door. Present research has been motivated by the need to reduce the possible clearance by enhancing torsional stiffness of the door of the microwave oven. Static deformation of the door frame of the oven is analyzed under a door-opening force. On the basis of the topological optimization, the right flange of the door frame is shown to need reinforcing. Several types of reinforcing brackets weldable to the right flange is proposed, and their effects to the stiffness of the door frame are compared and evaluated.