• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.513-520
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• 2005

The uniform truss mechanism is widely accepted as a shear transfer mechanism in reinforced concrete members. However, the uniform truss action cannot be expected when the bond stress distribution is not constant along longitudinal bars. A test method in which only the truss action takes place is developed and conducted to investigate the truss actions under various bond contributions. Based on the experimental results and analysis, the following findings can be obtained: 1) The bond stress distribution depends on the axial compression force, the amount of shear reinforcement and loading conditions. 2) The analysis using the combined truss model consisting of uniform and fan-shape trusses can predict the experimental results

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.45-52
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• 2012

A variety of retrofit material such as CFRP, GFRP, and PolyUrea have been developed for strengthening RC structures and infrastructures. From previously reported research results, the capacity of strengthened concrete structures was dictated by the behavior of the interface between retrofit material and concrete. In this study, bond-shear test was carried out to estimate the bond behavior between retrofit material and concrete using a newly developed test grip. The test results of load and slip relation and energy absorption capacity of each retrofit material were obtained. These test results will provide basic information for retrofit material selection to achieve target retrofit performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.1
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• pp.109-116
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• 2008

In order to test the adhesive capacity of carbon fiber sheet, a static loading method for bending-behavior-type beam specimens, cut in half was developed and test was conducted with compressive strength of concrete set as the test parameter. The tests were performed to prescribe adhesive shear strength based upon the result of shear failure as well as verification of testing method. First of all, the test method proved to be reliable in determining the adhesive shear strength. The test result also exhibited two types of variations in adhesive shear strength. Among two types of variations, average and minimum values for adhesive shear strength, relatively stable results, 3.41MPa and 2.11MPa, respectively. Particularity in the adhesive shear strength with respect to compressive shear strength was not found.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.377-387
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• 2017

The objective of this study is to investigate the influence that how does contact surface between concrete and steel influence the steel encased composite column by push-out test. Also nominal bond stress indicated by design standard such as Eurocode 4 is underestimated in small scale steel encased composite column. The other objective of this study is to investigate how does the number and space of shear connector influence the H-shaped steel encased composite column. The shear behavior of shear connectors is investigated by push-out test.

• Resources Recycling
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• v.10 no.1
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• pp.32-41
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• 2001

Bond shear strengths of recycled asphalt concrete were evaluated under different tack coat applications. Regardless of the new and old mixtures, the bond shear strengths at $30^{\circ}C$ were increased by 10-20% than those at 1$0^{\circ}C$. The bond shear strengths of recycled asphalt concrete without tack coat showed very low ones. These are the main reasons for the frequent longitudinal interface crack in the field. The effect of tack coat curing time on bond shear strengths was inferior to the tack coat construction temperature.

• Journal of the Korea Concrete Institute
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• v.21 no.3
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• pp.337-345
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• 2009

The purpose of this study is to investigate the shear strengthening effectiveness of the beams strengthened with near surface mounted (NSM) and external bonded (EB) CFRP strips. A total of nine concrete beams were made and tested. From this study, it was found that the shear stiffness and strength of the beams strengthened with NSM and EB strips were significantly improved compared to the control beam. Failure of the beam strengthened with NSM and EB strips was initiated by shear cracks, propagated diagonally to the adjacent epoxy grooves without crossing the epoxy and finally sudden diagonal crack connecting the point of application of load and flexural crack was occurred. For the beam strengthened combined with NSM and EB CFRP strips, the tensile strains in the NSM CFRP strips were observed in the range of 0.35% to 0.45% and strains with EB strips were measured about 0.3%.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.259-266
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• 2012

A general earthquake resistant design philosophy of ductile frame buildings allows beams to form plastic hinges adjacent to beam-column connections. In order to carry out this design philosophy, the ultimate bond or shear strength of the beam should be greater than the flexural yielding force and should not degrade before reaching its required ductility. The behavior of RC members dominated by bond or shear action reveals a dramatic reduction of energy dissipation in the hysteretic response due to the severe pinching effects. In this study, a method was proposed to predict the deformability of reinforced concrete members with short-span-to-depth-ratios, which would result in bond failure after flexural yielding. Repeated or cyclic loading produces a progressive deterioration of bond that may lead to failure at lower cyclic bond stress levels. Accumulation of bond damage is caused by the propagation of micro-cracks and progressive crushing of concrete in front of the lugs. The proposed method takes into account bond deterioration due to the degradation of concrete in the post yield range. In order to verify bond deformability of the proposed method, the predicted results were compared with the experimental results of RC members reported in the technical literature. Comparisons between the observed and calculated bond deformability of the tested RC members showed reasonably good agreement.

• Journal of the Korea Concrete Institute
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• v.22 no.4
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• pp.527-534
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• 2010

This study presents a simple method to improve the bond performance of reinforced concrete (RC) beams having high-strength shear reinforcement. In general, the yield strength and the ratio of shear reinforcements are the main parameters governing the shear capacity of RC beams. The yield strength of shear reinforcement, however, has little influence on the bond capacity of RC beams. Therefore, a sudden bond failure of the members with high-strength shear reinforcement can occur before flexural failure. To estimate the structural performance of the proposed method, four RC beams were cast and tested. The main test parameters were the yield strength, ratio, and reinforcing types of shear reinforcements. The experimental results indicated that the proposed method was able to effectively improve the bond performance of RC beams with high-strength shear reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.1
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• pp.41-47
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• 2016

This paper presents a bond test to find the effect of shear key and edge length from the bonded FRP in near surface-mounted(NSM) retrofit using FRP plate. Main parameters in the test are the location and size of shear key and the edge length. For the test, 10 specimens were made by embedding FRP plate of $3.6mm{\times}16mm$ into $400mm{\times}200(300)mm{\times}400mm$ concrete block and fixing it by using epoxy. Tensile load was applied to the FRP of the specimens until failure and was recorded at each load increase. In addition, the bond slip and elongation of FRP were measured during the test. From the test, it was found that the further the shear key located from the loading, the higher strength we could get. The bond strength inversely depended on the size of shear key. Especially, when the size of shear key was to be lagger than certain size, the bond strength decreased to very low value; even less than that of the case without shear key. The bond strength somewhat increased corresponding to the increase of edge length from the bonded end of FRP to loading in spite of same bond length. The bond-slip between FRP and concrete governed overall deformation in the bond test of NSM FRP so that the effect of excessive slip is necessary to be considered in the design.

• Journal of Korean Society of Steel Construction
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• v.13 no.3
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• pp.255-263
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• 2001

Longitudinal shear failure is the most common failure-type in composite slabs. In this paper, the shear-connection behavior of composite slabs with a particular profiled steel sheeting, so called ACE-DECK, having a depth of 60mm is studied experimentaly. Twenty two pull-out test specimens of different shapes, concrete topping thickness, and different steel sheeting thickness are carried out. It is founded that the shear connection behavior of composite slabs are not affected significantly in the steel sheeting thickness and concrete topping thickness. A new type of profiled steel sheeting is more effective in shear-bond strength that of existing flat-type deck plate, which can offer longitudinal shear strength in composite slope up to $3.6kgf/cm^2$