• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.160-170
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• 2010

Steel Fiber Reinforced Concrete (SFRC) beams has greater shear strength than typical reinforced concrete beams due to the high tensile strength of steel fibers. In this research, an experiment has been conducted to investigate the shear behavior of SFRC beams, and especially, the portion of shear resistance by uncracked compressive concrete section has been measured. Based on the test results in this study and 87 test data collected from literature, the accuracy of the existing equations for the estimation of shear strength has been evaluated. The shear strength of SFRC beams increased as more steel fibers were mixed. However, it is considered that the most efficient amount of steel fiber for enhancement of shear strength would be between 1% and 2% in that the specimen with 0.5% of steel fibers were abruptly failed after inclined cracking, and that the specimen with 2.0% of steel fibers showed a relatively low efficiency in increasing shear strength. The portion of shear resistance by the uncracked compressive concrete section was measured to be greater than 21%, and the equation proposed by Oh et al. provided the best accuracy on the estimation of shear strength of SFRC beams among the approaches evaluated in this study.

• Ecology and Resilient Infrastructure
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• v.5 no.3
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• pp.118-124
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• 2018

Social infrastructures and industrial complexes have been actively constructed in South Korea since the 1960 s as part of the economic development plan, resulting in rapid industrialization. However, side-effects due to the industrialization have occurred. An increase in industrial by-products or wastes is a typical problem. Although some industrial by-products are recycled in Korea as well as worldwide, some wastes are landfilled or dumped in the sea. Although many researchers have executed various technologies for the disposal of industrial wastes, economic and environmental technologies have not been developed. Thus, this study aims to activate paper and fly ashes during the crush process to overcome the drawback of simple concrete mixed with paper and fly ashes, which cause a reduction in workability and strength, derive an optimal content and replacement ratio of concretes mixed with Energetically Modified Material (EMM), and evaluate the material performance. In addition, the basalt fiber is mixed simultaneously to achieve the reduction of cracks and improve the tensile strength.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.23-29
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• 2023

The goal of this study is to evaluate the bursting characteristics and fire resistance performance of mixed cement concrete containing fibers at very high temperatures. For this purpose, FA-based, Slag-based, and each mix according to the amount of fiber mixed were heated to room temperature, 150℃, 300℃, 600℃, and 900℃, and then the burst shape, compressive strength, and elastic modulus were measured and evaluated. As a result of the experiment, it was found that relatively more surface damage occurred in FA-based specimens when heated at ultra-high temperatures than in slag-based specimens, and there was a difference between the mix without fibers and the mix with fibers when heated at ultra-high temperatures, that is, at 900℃. In the mix without fibers, a decrease in strength of more than 5% occurred. In addition, the elastic modulus also showed the same phenomenon as the compressive strength, and in particular, the decrease in elastic modulus was found to be greater than the amount of decrease in compressive strength. Meanwhile, estimation equations for compressive strength and elastic modulus according to heating temperature were statistically proposed.

• Journal of the Korea Institute of Building Construction
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• v.12 no.4
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• pp.442-450
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• 2012

In this study, fire resistance and residual strength were examined after the addition of PF fiber and bonding fireproofing gypsum board to a high strength concrete-model column of 50 MPa grade. At the beginning of the experiment, all the properties of base concrete appeared to satisfy the target range. In terms of the internal temperature record, a trend of slightly high temperature was shown when the fireproofing gypsum board was not bonding, and when the fireproofing gypsum board was bonding, as PF content increased gradually, the temperature was gradually lowered. In terms of the relationship, as time elapsed a low temperature was shown when fiber was mixed, and when the board was bonding, the trend of lower temperature could be confirmed. Meanwhile, in terms of spalling property, a severe explosive fracture was generated at PF 0%, and falling off was prevented as the fiber content was increased; however, discoloration and a multitude of cracks were discovered, and when the board was bonding, the trend in which the exterior became satisfactory when the content was increased emerged. In terms of the residual compressive strength, measuring of strength could not be performed at PF 0% without bonding of board, and the strength was increased as the fiber content was increased; however, there was a decrease in strength of about 30 ~ 40%, and in the case of PF 0% with the bonding of board, the strength could be measured; however, about an 80% decrease in strength was shown, and only about a 10 ~ 20% decline in strength was displayed, as the range of decrease was reduced as the fiber content was increased. Considering all of these factors, it was determined that a more efficient enhancement of fire resistance was obtained when two methods are applied in combination rather than when the PF fiber content and bonding of fireproofing gypsum board are utilized individually.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.75-76
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• 2012

In this study, it was evaluated about creep properties of high strength concrete according to compressive strength and moisture evaporation condition. As a results, creep strain and creep coefficient was greatly affected by moisture evaporation conditions rather than compressive strength. Also, the effect of fiber mixed was not show big difference.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.199-200
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• 2021

In the study, creep and dry shrinkage characteristics were evaluated to determine the material properties necessary for structural analysis such as column shortening and differential drying shrinkage. All the experiments were conducted in an constant temperature and humidity room. The mechanical properties as well as the specific creep and ultimate dry shrinkage values were derived. In addition the characteristics of the physical value of the high-strength fiber reinforced concrete were considered.

• International Journal of High-Rise Buildings
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• v.13 no.2
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• pp.187-194
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• 2024

The 53-meter tall Albizzia Tower is a white, mineral building with a mixed concrete and wood structure. It harmoniously interacts with the high rises of La Confluence. Its base is largely open, in direct relation to the public space. The spaces are mutable, reversible, moldable thanks to a streamlined structure: posts, beams in glued laminated wood, with posts pushed back on the facade to facilitate the layout of office and housing floors, CLT floors with a span of 7 meters.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.21-28
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• 2015

Recent studies on concrete floating structure development focused on connection system of concrete modules. Precast concrete modules are designed to be attached by prestressing in the water, exposing the structure to the loads from water and making the construction difficult. Therefore, a development of bond material became a key issue in successful connection of floating concrete modules. In this study, micro-silica mixed aqua epoxy (MSAE) is developed for the task. Existing primer aqua epoxy, originally used as a bond material for the retrofit of concrete structures using fiber reinforced polymers, is evaluated to find the optimum micro-silica added mix proportion. Micro-silica of 0~4 volume % was mixed in standard mixture of aqua epoxy. Then, the material property tests were performed to study the effect of micro-silica in aqua epoxy by controlling the epoxy silane proportion by 0, ${\pm}5$, ${\pm}10%$. The optimum mix design of MSAE was derived based on the test results. The MSAE was used to connect concrete module specimens with the epoxy thickness variation of 5, 10, and 20mm. Then, 3-point loading test was performed to verify the bond capacity of MSAE. The results show that MSAE improves the bond capacity of concrete module.

• Journal of the Korea Concrete Institute
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• v.29 no.2
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• pp.209-216
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• 2017

One of the important considerations in structural designing the flat plate system is ensuring the resistance to punching shear caused by axial loads and the ductile ability to follow horizontal deformation under earthquake. In this study, the ECC (Engineered Cementitious Composite) has been placed in the critical section zone of punching shear at slab-column joint to improve ductility and the advanced details of shear reinforced area nearby critical section zone has been developed using stud and steel fiber. The shear performance tests were performed on the specimens with parameters of fiber type mixed with ECC, stud and steel fiber set into the shear reinforced area in which the failure pattern, joint strength, displacement and strain of the specimen were compared and analyzed. The test results showed that the strength and ductility of specimens with ECC applied to joint were better than those of RC flat plate system. Also, the shear reinforcement effect of stud and the ductility improvement of steel fiber concrete were confirmed in the shear reinforcement area.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.865-868
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• 2008

As a part of a series of study, this study reviewed the fire proof characteristics of high performance concrete RC column members using non-stripping form that accompanied metal lath lateral confinement to prevent spalling of high performance concrete which is increasingly used recently, and the results are as follows. Flow and air amount both satisfied target range, and compressive strength, over 80MPa at age 28 days, showed high strength range. As for spalling characteristics, in the case of plain in which no fiber is mixed, severe spalling occurred, and in the case of 0.05% nylon("NY" hereinafter)+polypropylene("PP" hereinafter) fiber mixture, only surface area experienced partial spalling. Regarding non-stripping form changes, both non-stripping 25-20 and non-stripping 50-20 experienced spalling at finish material area, and non-stripping 50-20 showed better spalling proof performance than non-stripping 25-20. In the case of non-stripping 50-40, spalling was prevented, and while mass reduction rate was less than 10%, its temperature hysteresis showed the most excellent fire proof performance with base metal surface area maximum temperature $376.1^{\circ}C$.