• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.169-178
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• 1998

Bond strength of reinforcing bar to high-perfomance concrete using belite cement is explored using beam end test specimens. The key parameters for the bond test are slump of concrete, top bar effect, and strength of concrete in addition to concrete cover. The test results show that the specimens with belite cement concrete show approximately 10% higer bond strength than those with portland cement concrete. The results also show that the bond strength from the high strength concrete is function of the square root of concrete compressive strength. Bond strength of the top bar is less than bond strength of bottom bar, but the ratios of the bond strength of bottom-cast bars to those for top-cast bars are much less than the modification factor for top reinforcement found in the ACI 318-95 code. Comparisons with other reported tests identified that belite cement increased bond strength while silica fume or flyash used in high strength concrete decreased bond strength. The high-strength and high-slump concrete with belite cement performs well in terms of bond strength to reinforcing steel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6565-6574
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• 2013

Precast concrete blocks are used mainly for score protection, slope protection and riverbed structure protection, etc. Because these concrete blocks are exposed to water or wetting environments, the steel rebar used as reinforcements in concrete blocks can corrode easily. Corrosion of the steel rebar tends to reduce the performance and service life of the concrete blocks. In this study, Glass Fiber Reinforced Polymer(GFRP) rebar, which does not corrode, was applied instead of a steel rebar to prevent performance degradation of the blocks. Recycled concrete aggregate and high early strength cement(HESC) were used in the concrete mix for field applicability. The experiment results showed that the workability and form removal strength of the recycled aggregate concrete using HESC showed comparable results to normal concrete and the compressive strength at 28 days increased by about 18% compared to normal concrete. The load resistance capacity of the recycled aggregate concrete blocks reinforced with a GFRP rebar increased by approximately 10~30% compared to common concrete block.

• Geotechnical Engineering
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• v.14 no.6
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• pp.57-71
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• 1998

Present bonding methods which connect steel pipe and spread footing in pile foundation have been generally used. These methods however showed lots of difficulties in the quality control. A new bonding method, which is called 'Bolted Bonding Method(BBM)' , is developed. This method uses factory-made parts so that it may increase the degree of quality, and workability, and is being adopted in the Held concerned. The method is verified by the structural analysis and laboratory test and then a new design formula is proposed. In addition, a comparison test of the present methods and BBM are conducted to observe the applicability and economy of the latter. As results, it is observed that BBM shows 5 to 10 times faster in Held work and 9% to 50% cheaper in construction cost than the existing methods.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.851-854
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• 2008

Using the recycled aggregate not only saves landfill space but also reduces the demand for extraction of natural raw material for new construction activity. However few investigations have been carried out to study the shear behaviors of RC beams with recycled aggregates such as low absorption of recycled aggregate and full-scale specimens. In this study, six reinforced concrete beams were tested to evaluate the effects of shear strength, and shear behavior on the replacement level (0, 30, 60, and 100%) of recycled coarse aggregate and different amounts of shear reinforcement. The results showed that the beams with recycled coarse aggregates present the similar shear strength and deflections as the beam with natural aggregate on an equal amount of shear reinforcement. the reinforced concrete beams with recycled coarse aggregates present the Influence of shear span-to-depth ratio, effective depth, tension reinforcement ratio and compressive strength as the beams with natural aggregate. Shear strength were compared with the provisions in current code (KCI2007) and the equation proposed by Zsutty. The KCI equations were conservative and subsequently can be used for the shear design of recycled aggregate concrete beam.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.801-804
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• 2008

Fiber reinforced plastics (FRP) are light in weight, non-corrosive and exhibits high tensile strength. FRPs having superior material properties to corrosive steels have been widely replacing steel bars or tendons used in concrete structures as flexural reinforcements. Although current design guidelines for estimating shear strength of FRP concrete beam follow the format of conventional reinforced concrete design method, there are noticeable differences among the existing formulas in calculating the contributions of concrete to shear resistance. In this paper, the artificial neural network (ANN) technique is employed as an analytical alternative to existing methods for predicting shear capacity of FRP concrete beams. Influential factors on shear strength were identified through literature review and input in ANN and the ANN was trained for the target ultimate shear obtained from database. The results from ANN were compared with existing formulas for its accuracy. It was found that the developed ANN were more closely predicting the test data than those of the currently available predictive equations.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.899-902
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• 2008

The GFRP rebar have been interested as the substituting material of the conventional steel rebar to the concrete structure for high durable concrete structure. The GFRP rebar, however, has different way to be fabricated and mechanical characteristics comparing with the conventional steel rebar. Therefore, to apply the GFRP rebar to the construction field, it needs the proper and reasonable design theory, codes and guidelines. In this study, for the design recommendation of the GFRP rebar, ACI440.IR and ISIS Canada design manual were investigated and concluded that the design theory of ISIS Canada design manual was relatively better design concept considering the limit state of the GFRP rebar in design and analysis. With this design concept, new design equation for the GFRP rebar was suggested and investigated with other design equations.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.275-281
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• 2007

Recently, steel-concrete composite structures are widely used in bridge and building constructions. In this paper, a new type of steel-concrete composite deck with profiled steel sheeting is proposed to replace the conventional cast-in-place reinforced concrete deck. Perfobond rib shear connectors were utilized to provide horizontal shear resistance between the profiled sheeting and the concrete. To validate the effectiveness of the proposed deck system, 8 full-scale deck specimens for PSC girder bridge were fabricated. The specimens were tested with four different shear span lengths to determine the horizontal shear resistance of the deck under a static monotonic loading. For comparison purpose, two reinforced concrete decks were also fabricated and tested. The horizontal shear resistance of the proposed deck system was calculated using the m-k method.

• Magazine of the Korea Concrete Institute
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• v.6 no.3
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• pp.173-179
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• 1994

Test results to evaluate the rr~echanical properties of epoxy-coated reinforcing bars are described. Tests include adhesion, impact, bend, and abrasion test of epoxy coating to reinforcing steel, specified in relevant KS and ASTM standards. Three nomnal thicknesses of epoxy coating, $120{\mu}m$, $220{\mu}m$, $300{\mu}m$ are used. The results show good adhesion and abrasion resistance satisfying the requirements. The results also show faily good bendability. However, the thicker the coating, the weaker the adhesion is. Impact resistance is in the tolerable range, but it is recorrmerided that careful treatments are required during handling of epoxy-coated bars. From the results, epoxy-coated bars, with a coating thickness ranging from $150{\mu}m$ to $300{\mu}m$, should well perform for fabrication in field construction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.155-162
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• 2011

The structures that use the bridge plates are considered to have advantages such as short work term, excellent economical efficiency and low maintenance cost. Bridge plates are being widely used for water ducts and eco-corridors as replacements of reinforced concrete ducts. Bridge plates are deep and have greater pitch as compare to conventionally deep corrugated steel plate. They are expected to be increasingly used in the future. The structures that use bridge plates have two forms, such as arch type and box type. The arch type structures are designed based on the compressive strength, and the box type structures, based on the moment in the plate member. In this study, the ultimate strength and moment strength of the connection part of the specimens were examined by their thickness. Static and bending tests used to evaluate the performance of bridge plate. Finally, These results were used in the design process.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.205-208
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• 2008

Using the recycled aggregate can reduces the landfill space, the demand for natural raw material for new construction. Some investigations have been carried out to study the shear behaviors of RC beams with recycled aggregates. But these have some limitation due to the use of low quality recycled aggregates and small-scale specimens in the laboratory. In this study, four full-scaled RC beams were tested to evaluate the effects of replacement level (0,30, 60, and 100%) of recycled fine aggregate on shear behavior of RC beams. The results showed that the beams with recycled fine aggregates show similar crack pattern and failure mode compared with the beam with natural aggregate. Also, the beams with recycled fine aggregates present the similar shear strength except the one with the replacement level of 100% recycled fine aggregates. Shear strength were compared with the provisions in current code (KCI2007) and the equation proposed by Zsutty. The KCI equations were conservative and subsequently can be used for the shear design of recycled aggregate concrete beam.