• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.527-534
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• 2016

Beams strengthened in shear with Carbon Fiber Reinforced Polymer (CFRP) which had different transverse reinforcement ratio were tested to evaluate shear contribution in the CFRP and to analyze shear behavior of each test with Mohr's circle. Strain in the CFRP should be evaluated to estimate the shear contribution in the CFRP which is brittle material. Test results were compared each other based on the Mohr's circle which can correlate shear strain with both principal tensile strain and crack angle. With low transverse steel ratio, shear strengthening with CFRP not only increases the shear strength effectively but also minimizes the loss in shear contribution of concrete by limiting the development of crack. With high transverse steel ratio, the effect on shear strengthening with CFRP is not as much as the beam with low ratio. Therefore, the shear contribution in the CFRP should be evaluated based on the strain compatibility which can consider the interaction between steel and CFRP when determining the shear capacity of a strengthened member.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.75-83
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• 2014

In order to prevent brittle failure of concrete, steel fiber reinforcement is effective composite material. However ductility of steel fiber reinforced concrete may be limited due to shrinkage caused by large content of cement binder. Chemical prestressing for steel fiber reinforcement in cement matrix can be induced through expansive admixture and this can increase reinforcing effect of steel fiber. In this study, mechanical performances in concrete with CSA (Calcium sulfoaluminate) expansive admixture and steel fiber reinforcement are evaluated. For this work, steel fiber reinforcement of 1 and 2% of volume ratio and CSA expansive admixture of 10% weight ratio of cement are added in concrete. Mechanical and fracture properties are evaluated in concrete with steel fiber reinforcement and CSA expansive admixture. CSA concrete with steel fiber reinforcement shows increase in tensile strength, initial cracking load, and ductility performance like enlarged fracture energy after cracking. With appropriate using expansive admixture and optimum ratio of steel fiber reinforcement, their interactive action can effectively improve brittle behavior in concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4298-4307
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• 2015

The expenses of maintenance and reinforcement for aged concrete structures are significantly on the increase as their durability and general performance has been naturally degraded. Due to this reason, interests on concrete crack reduction technology are growing but more researches are required to fulfill such fast growing demands. Particularly in the underground power facilities, it is difficult to maintain the quality of aging concrete spheres for underground power as their deterioration caused by long-term operation is on-going. In recent years, many studies have been made to overcome the issues and now it is determined that the shrinkage reducing technology which can dramatically reduce the crack at the design stage is one of the most effective solutions. In this study, the test investigated fundamental propertiesof concrete using various shrinkage reducing materials to develop low shrinkage mortar. According to results of experimental study, for mortar and concrete, glycol based material showed excellent shrinkage property and compressive strength. For the later study to generic application of the shrinkage reducing materials, performance reviews on the shrinkage reducing materials with variable factors and various materials such as changes in the amount and type of materials should be followed.

• Journal of the Korea Institute of Building Construction
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• v.11 no.5
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• pp.419-425
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• 2011

Topping concrete that is not reinforced with rebar to prevent poor tensile performance is vulnerable to cracking. In this study, jute, which is known to be an excellent natural fiber material for strengthening concrete performance, was compared with other cellulose fibers in terms of its capacity to reduce the cracking of concrete. As a result, it was found that compared with concrete using other fibers, concrete using jute fiber showed more than a 50 % reduction of plastic shrinkage crack resistance with the contents of 0.9 kg/$m^3$ and 1.2 kg/$m^3$ for. For impact strength tests, the final destruction of WF and PULP fibers took up to 5 times the number of falls, while jute has 10-18 circuitry, showing excellent ductility properties.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.568-575
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• 2023

This paper aims to evaluate the quality characteristics and healing performance of precast concrete incorporating self-healing technology as a key technique for the construction of smart cities. The study found that precast concrete mixed with hybrid capsules exhibited a tendency of reduced slump and air content, impacting the quality characteristics. Specifically, the slump decreased by up to 14 %, and the air content by up to 9 %. Moreover, the inclusion of hybrid capsules in the concrete resulted in a maximum decrease of 16 % in compressive strength and 18 % in flexural strength. However, the introduction of hybrid capsules significantly enhanced the crack healing performance. The assessment through water permeability tests showed that the healing rate of 0.3 mm crack width after a 28-day healing period improved as the mixing ratio increased, with the healing rates at 1 %, 3 %, and 5 % hybrid capsule mixtures observed to increase by approximately 16 %, 25 %, and 32 %, respectively.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.409-410
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• 2009

The eco-cement concrete using fly-ash was produced for the improvement of the compressive strength of the eco-cement concrete under the long term age, and compressive strength test, drying shrinkage test, uniaxial restraint shrinkage cracking test, and bond test were carried out. In this study, the cracking resistance performance was investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.411-412
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• 2010

The objective of this study is to analyze crack occurrence of small scale structure fabricated with high strength concrete with 80 MPa using polylon fiber after fire. It is found that the addition of polylon fiber resultsd in reducing cracks by as much as 23.4% compared with plain concrete.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.660-663
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• 2019

본 논문은 진공을 이용한 흡착방식과 바퀴형 이동방식을 사용하는 벽면이동로봇의 균열 위치 추정에 관한 연구로써, 로봇의 Yaw값에 대해 PID제어를 통해 로봇의 방향을 제어 하고 이를 바탕으로 엔코더 모터의 홀센서와 IMU를 기반으로 하여 균열 위치를 추정 한다. 위치 추정 성능을 검증하기 위해 실제 위치와 추정된 위치를 비교하고 결과를 제시하였다.

• Proceedings of the Korean Institute of Landscape Architecture Conference
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• 2020.06a
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• pp.81-82
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• 2020

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.4
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• pp.49-56
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• 2015

Ultra-High Strength Concrete(UHPC) has ultra-high material performance including high strength and high flowability. On the other hand it is less ductile than high ductile fiber reinforced cementitious composite. This study investigated the effect of combination of steel fiber and micro fiber on the tensile behavior of UHPC. Four types of UHPC containing combination of steel fiber, polyethylene(PE), polyvinyl alcohol(PVA), and basalt fiber were designed. And then uniaxial tension tests were performed to evaluate the tensile behavior of UHPC according to combination of fibers. And density was measured to evaluate whether micro fiber induces unintentional high pore or not. From the test results, it was exhibited that PE fiber with high strength is effective to improve the tensile behavior of UHPC and basalt fiber is effective to increase the cracking and tensile strength of UHPC. Furthermore, it was also verified that micro fiber does not make high pore.