• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.619-626
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• 2008

There have been numerous studies to develop eco-friendly concrete. The attempt to reduce the amount of cement usage is suggested as one of the solutions for eco-friendly concrete. To reduce the amount of cement usage, the pozzolan-reaction materials such as ground granulated blast furnace slag, fly ash, and meta kaolin are widely used as the mineral admixture. Hwangtoh which deposited broadly in Korea is a well known eco-friendly material and the activated Hwangtoh with pozzolan-reaction can be practically used as a mineral admixture of concrete. Meanwhile, PET fiber made of recycled PET bottle is a type of recycled material, which can be used to control micro cracks in concrete. But the study about concrete mixed with recycled PET fiber is insufficient and the research of Hwangtoh concrete mixed with PET fiber is urgently needed presently. In this study, experiment and analysis flexural behavior of Hwangtoh concrete blended with recycled PET fiber are carried out. The results are discussed in detail.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.505-511
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• 2005

This experimental investigation was conducted to examine the seismic performance of reinforced concrete bridge columns. The columns were subjected to a constant axial load and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research were the volumetric ratios of transverse reinforcement (ps=0.96, 1.44 percent) and axial load ratios (P/Po=0.05, 0.1, 0.2) and concrete strengths (35, 60MPa). Test results showed that bridge columns with $44\%$ higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behavior. For bridge columns with axial load ratio(P/Po) less than 0.2, the ratio of $M_{max}\;over\;M_{ACI}$, nominal moment capacity predicted by ACI 318-02 provisions, was consistently greater than 1 with approximately a $20\%$ margin of safety.

• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.27-35
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• 2012

Facings of mechanically stabilized earth retaining walls have function to fix the reinforcement and prevent backfill loss, but the walls are lack of structural rigidity capable of resisting applied loads. The reinforced subgrade with rigid wall was developed to have the structural functions under train loading. Though it has lots of advantages such as small deformation after construction, its negative side effects of economics and difficult construction were mainly mentioned and not practically used. To apply it for railroad subgrade, this study focus on the construction cost down and the enhancement of constructability without functional loss. To do so, the behaviors of reinforced subgrade with rigid wall were evaluated with the change of the vertical spacing and length of reinforcement. Small scale model tests (1/10 scale) and 3 m full scale tests were performed to evaluate deformation characteristics of reinforced subgrade under simulated train loading. Even though it uses short reinforcement, it showed small horizontal displacement of wall and plastic settlement of subgrade. Also, it was verified that not only 30 cm but also 40 cm of vertical spacing of reinforcement had good performance in serviceability aspects.

• Journal of the Society of Disaster Information
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• v.18 no.4
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• pp.930-935
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• 2022

Purpose: The purpose of this study is to evaluate the stiffness reduction and damping ratio of reinforced concrete hollow slabs and to analyze their performance, and to study the effect of the damping effect of hollow bodies and the stiffness reduction on the serviceability of slabs. Method: Test specimen was made in a size of 0.6m^*0.21m^*3.6m to evaluate the vibration effect of the slab, and the hollow ratio was set in six steps from 0.0% to 30% to measure the change in rigidity and damping according to the change in the hollow ratio. Result: As the hollow ratio increases, rigidity decreases and the natural frequency decreases, but as the mass decreases, the natural frequency increases gradually. Since energy is hardly dissipated up to the hollow ratio of 20%, the hollow ratio should be reduced by 30%. Conclusion: It was found that the bending strength degradation of the slab with a hollow ratio of about 30% is minimized, but an appropriate natural frequency can be maintained, and a certain damping effect can be obtained.

• International Journal of Highway Engineering
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• v.5 no.3 s.17
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• pp.11-20
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• 2003

Concrete structures such as bridges, pavement, and offshore structures are normally subjected to repeated load. Because highway and airfield pavements are to resist tension in bending, fatigue failure behavior is very important the fatigue life of materials. Therefore, in this paper was carried according to the fatigue test method and experiment variables for pavement concrete. The fatigue tests were applied split tension($150{\times}75$ in size) and flexural($150mm{\times}150mm{\times}550mm$ in size) beam fatigue test method. Major experimental variable in the fatigue tests in order to consideration of fatigue life were conducted loading frequency of 1, 5, 10, 20Hz and loading shape of block, sine, triangle and moisture condition of dry and wet condition and curing age of 28day and 56day. The test results show that the effect of loading frequency increasing the frequency increased fatigue life, decreased significant at frequencies below 200 cycles. The effect of loading wave form on fatigue life show that a block decreased, triangular increased in comparison with sine. The effect of moisture condition decreased in wet condition in comparison with dry condition. The effect of curing age increased in 564ays in comparison with 28day.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.141-148
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• 2016

This paper employed finite element method (FEM) to study the dynamic response of Steel Fiber-Reinforced Concrete(SFRC) panels subjected to impact loading by spherical projectiles. The material properties and non-linear stress-strain curves of SFRC were obtained by compression test and flexural test. Various parametric studies, such as the effect of fiber volume fraction and thickness of panels, are made and numerical analyses are compared with experiments conducted. It is shown that protective performance of concrete panels will be improved by adding steel fiber. Area loss rates and weight loss rates are decreased with increasing fiber volume fraction. Also, penetration modes can be expected by FEM, showing well agreement with experiment. Results can be applied for designing the protection of military structures and other facilities against high-velocity projectiles.

• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.9-15
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• 2018

Radon gas, which is present on the earth, is a primary carcinogen released from rocks, soil, building materials, etc., and exists as a unique gas phase. In order to solve the risk of radon gas, we evaluated the basic performance which can be used as indoor finishing materials in addition to the radon gas reduction properties of the matrix using anthracite. An anthracite used as a conventional filter material was used to produce a matrix, and a test was conducted to replace the gypsum board, which is one of the building materials used in the existing room. As the anthracite replacement ratio increases, flexural failure load strength increases and thermal conductivity tends to decrease. Depending on the thickness of the board, the reduction performance of radon gas shows a slight difference.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.121-127
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• 2010

An experimental study of composite beam with perforated fiber reinforced polymer(FRP) plank as a permanent formwork and the tensile reinforcement was performed. A combined formwork and reinforcement system can facilitate rapid construction of concrete members since no conventional formwork is needed, which requires time consuming assembly and dismantling. In order for a smooth FRP plank to act compositely with the concrete, the surface of the FRP needs to be treated to increase its bond properties. Aggregates were bonded to the FRP plank using a commercially available epoxy and perforated web of plank. No additional flexural or shear reinforcement was provided in the beams. For comparison, two control specimens were tested. One control had no perforated hole in the web of FRP plank and the other had internal steel reinforcing bars instead of the FRP plank. The beams were loaded by central patch load to their ultimate capacity. This study demonstrates that the perforated FRP plank has the potential to serve as a permanent formwork and reinforcing for concrete beam.

• Journal of the Society of Disaster Information
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• v.8 no.4
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• pp.391-400
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• 2012

Recently, the construction industry commonly uses FRP as a reinforcement material because of its material advantages. FRP attached reinforcement has various advantages such as high strength, stiffness, excellent durability and construction practicability comparing to its weight. However, external attachment of FRP is water-tighted with low water permeable material, not draining water, probably causing damages on a permanent structure. The study manufactured it through pultrusion and examined GP(glass fiber panel) of which material-mechanical properties are almost same as the existing FRP but durability and attachment performance are better by stationary experiments, testing load-deflection curve, destruction types and load-deflection relation under repetitive loading test. As a result of 2,000,000 fatigue tests, it did not result in the destruction and showed excellent permanent attachment and durability as it displays significantly low compressive strain of concrete.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.161-168
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• 2010

The bonded tendon was adopted to the reactor building of some operating nuclear power plants in Korea and the assessment of the effective prestress force on the bonded tendon is being issued as an important pending problem for continuous operation beyond their design life. The sensitivity analysis of various parameters was carried out to evaluate the effective prestress force using the system identification technique and the optimal parameters were determined for SI technique in this study. The 1/5 scaled post-tensioned concrete beams with the bonded tendon type were manufactured and in order to investigate the relationship of the natural frequency and the displacement to the effective prestress force, impact test, SIMO sine sweep test and bending test using the optical fiber sensor and the compact displacement transducer were carried out. As a result of tests, both the natural frequency and the displacement show the good relationship with the effective prestress force and both parameters are available for the SI technique to estimate the effective prestress force.