• 한국도로학회:학술대회논문집
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• 2000.11a
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• pp.191-197
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• 2000

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.3
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• pp.19-26
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• 2024

In this study, the compressive behavior of a 1/12.5 scale model of a wind tower support structure connection was experimentally analyzed. A high-performance cementitious grout with a compressive strength of 140 MPa was used to fill the connection, and experiments were conducted with shear key spacing, the shape, and connection length as variables. When the number of shear keys in the connection is the same, the smaller the spacing of the shear keys than the length of the connection, the higher the shear strength, and for the same spacing and connection length, the higher the height of the shear keys, the higher the strength. In addition, it was found that the strength showed a linear behaviour until the connection slip reached 1.0 mm, and it reached the maximum strength at 7.0 mm connection slip showing a non-linear behaviour as the load increased. It was found that the failure mode changed from interfacial shear failure to grout failure as the strength increased according to the shape and spacing of the shear key, and brittle failure did not occur due to steel fibers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.144-152
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• 2010

In this study, cement-based filler is used as an adhesive instead of organic adhesive, epoxy because there were problems under wet condition. First, the bond strength of cement-based filler was measured and the result was satisfied with KS F 4716. However, in case of wet condition, bond strength of epoxy adhesive decreased $0.73N/mm^2$ in 7 days and $0.84N/mm^2$ in 14 days from pilot test. This implies that there would be a problem on reinforced concrete structure in wet condition, such as tunnel and sewage box. In the second experiment, the flexural strength of RC beams with GFRP using different thickness of cement-based filler was investigated, and the result was indicated 113%, 66%, 75% increase in 10mm, 20mm, 30mm thickness, respectively. From the result, it was known that 10mm filler thickness produces stable bond performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.5
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• pp.55-64
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• 2008

Shotcrete have become a deterioration which was exposed to harmful environments. In this study, in order to evaluate the deterioration properties of shotcrete, visual examination, compressive strength, adhesive strength, microstructural analysis were investigated up to the 60th weeks of exposure. The attack solutions for test are sodium sulfate and hydrochloric acid solution with different concentrations, respectively. From the results, although the compressive strength of shotcrete specimens and the adhesive strength between specimens and rocks were high at the early immersion age, they rapidly dropped in the subsequent phases, especially in 5% sodium sulfate and pH1 hydrochloric acid solution. With continued exposure, various harmful ions penetrated into the shotcrete specimen, reacted with the cement hydrate, and generated expansion substances. It was verified that the shotcrete specimens suffered a serious deterioration by chemical attack.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.5
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• pp.7-13
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• 2008

This paper presents experimental and analysis studies about both the corroded steel expansion and the variation of poor bonding range between steel and concrete. A loss of overall bonding capacity at the concrete-steel interface is evaluated experimentally and crack patterns at the bottom of the concrete are presented here. Steel-concrete interface is covered by rubber due to present local loss of the concrete-steel interface bonding capacity. In case of crack analysis performed by commercial FEM programs. we investigated crack‘s pattern and location. Finally, it is concluded that overall flexural capacity of the reinforced concrete structure is increased by the corroded steel expansion and is dependent of the bonding range at the steel- concrete interface. These results give an important factor to decide a life of reinforced concrete structures.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.451-456
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• 2015

This study aimed to evaluate of the hardened properties (mortar consistency, setting time, absorption properties, drying shrinkage, and bond strength) of the basalt powder sludge mortar recycling a basalt powder sludge occurred during the manufacture process of basalt stone as a replacing material for the sea-sand used to cement filling compound for surface preparation. The hardened mortar made of the basalt powder sludge showed an enhanced performance or similar with the properties of normal mortar used to cement filling compound for surface preparation. But, the drying shrinkage was increased more than a normal cement mortar in the hardened mortar made of the basalt powder sludge since curing 8 - 9days. And the bond strength is low in the hardened mortar used the basalt powder sludge. On the whole, properties of the hardened mortar used the basalt powder sludge correspond to the required minimum quality criterion in the KS F 4716 'cement filling compound for surface preparation'.

• Journal of the Korea Concrete Institute
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• v.22 no.1
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• pp.77-84
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• 2010

Latex modified concrete (LMC) exhibits improved material properties including high tensile strength and durability compared with conventional concrete, and hence LMC has been used as protective layers over the bridge deck slabs to increase their service life with underlying assumption of excellent bond behavior between the LMC overlay and the concrete substrate. In this study, the effect of the primary parameters of the concrete substrate (i.e., shrinkage, stiffness and cracking capacity) as well as the LMC overlay thickness on the probability of cracking of the bridge deck slabs using LMC overlays was investigated by carrying out the finite element analysis that simulated the bond behavior of LMC overlays on normal strength concrete (NSC) and HPC bridge deck slabs. Based on the results of the numerical analysis, it is concluded that the relatively high shrinkage strains and stiffness of HPC slabs can increase its probability of cracking in bridge deck slabs using LMC overlay.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.5
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• pp.1-8
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• 2020

This study presents a shear strength estimation model, in which the shear failure of a reinforced concrete (RC) member is assumed to be governed by the flexure-shear mechanism. Two shear demand curves and corresponding potential capacity curves for cracked tension and uncracked compression zones are derived, for which the bond mechanism developed between reinforcing bars and surrounding concrete is considered in flexural analysis. The shear crack concentration factor is also addressed to consider the so-called size effect induced in large RC members. In addition,unlike exising methods, a new formulation was addressed to consider the interaction between the shear contributions of concrete and stirrup. To verify the proposed method, an extensive shear database was established, and it appeared that the proposed method can capture the shear strengths of the collected test specimens regardless of their material properties, geometrical features, presence of stirrups, and bond characteristics.

• Journal of the Korea Institute of Building Construction
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• v.21 no.6
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• pp.519-527
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• 2021

In this study, an electromagnetic pulse shielding effect was obtained by applying the arc metal spraying method to the ordinary concrete. For this study, to evaluate the electrical properties in the thickness of the metal sprayed coating, 8 types of metals(Cu, CuAl, CuNi, CuZn, Al, Zn, ZnAl, AlMg) were sprayed as coatings with a thickness of 100, 200 and 500㎛. The electrical conductivity on the surface was measured with a 4-pin probe, and an electromagnetic wave shielding effect test was performed according to KS. Based on the test results, 200 ㎛ was proposed as an optimal metal coating thickness for electromagnetic pulse shielding, and it was thermally sprayed on a 300×300×100mm concrete specimen to analyze the electromagnetic wave shielding performance. However, in the area of adhesion strength, the maximum was 1.11MPa, which was found to be less than 74% of the target performance.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.119-126
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• 2022

This study proposed a BCM(Binding Column Method) that can reinforce the insufficient seismic force of piloti buildings that are not designed for seismic resistance. In addition, 4 reinforcement specimens and 1 reference specimen were manufactured for the proposed seismic reinforcement method. The effect of improving seismic performance before and after reinforcement was examined through repeated loading tests. As a result of experiment, seismic reinforcement specimen with BCM system showed hysteretic characteristics of a large ellipse with great energy dissipation ability and increased strength and stiffness, while reference specimen showed rapid reduction in strength and brittle shear failure column. In addition, it can be seen that the reinforcing effect is improved as the gap is narrow, the torque is large, and the thickness of the L-shaped steel sheet is thicker. The SC4 specimen showed the best seismic performance reinforcement effect.