• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.11
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• pp.750-757
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• 2018

The mechanically stabilized earth wall abutment is an earth structure using a mechanically stabilized earth wall and it uses in-extensional steel reinforcements having excellent friction performance. In order to analyze the pullout behavior of in-extensional steel reinforcements usually applied on the mechanically stabilized earth wall abutment, effects of stiffness and particle-size distributions of backfills and also horizontal spacings were considered in this study. As a result of parametric analyses, the highest pulling force acted on the uppermost reinforcement, and the stiffness and the particle-size distributions of the backfill significantly affected the pulling resistance of the reinforced soils. The internal friction angle of backfills should be at least 25 degrees, the coefficient uniformity factor should be at least 4, and the horizontal spacing of the uppermost steel reinforcement should be less than 25cm. Therefore, in order to secure the pullout resistance of the reinforced soil, it is necessary a properly spacing of reinforcement and more strict quality control for the backfill.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.454-457
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• 2009

관이음부는 다양한 장점을 가지고 있어 여러 분야에 널리 이용되며, 관이음부의 구조강도를 증가시키기 위해 내부에 환보강재를 설치하는 방법이 대형 강관구조물에서 사용되고 있다. 그러나 환보강 관이음부의 해석 및 설계 자료에 관한 연구는 미흡한 실정이므로, 보강재의 기하학적 특성과 정적강도와의 관계를 규명하고자 한다. 환보강 K형 관이음부의 정적강도에 대하여 수치적으로 검토하기 위해 원형 중공단면의 관이음부를 유한요소 모델링하였고, 각 부재의 직경, 두께 및 폭의 상관관계를 이용한 무차원 계수를 통해 보강재의 위치와 기하학적 형상에 따른 보강효과를 수치적으로 검토하였다.

• Computational Structural Engineering
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• v.11 no.3
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• pp.165-172
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• 1998

본 연구에서는 종이 충격흡수의 효율적인 기하형상이 연구되었다. 일반적으로 충격흡수재는 골판지, 스폰지, 종이, 고무등으로 제작된다. 에너지 흡수거동에 대한 종이 충격 흡수재의 보강형태, 크기., 재료 특성에 대한 영향이 ABAQUS/Explicit5.5에 의한 유한요소 해석과 미끄럼 충격시험을 통해 연구되었다. 종이 충격 흡수재의 최대 변위는 충격속도에 따라 증가하며, 내부단수에 따라 감소하였다. 충격이력 특성은 내부단수가 7단일 때 5 msee까지 급속히 변형되며, 그 이후에는 영구변형으로 존재한다.

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.175-181
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• 2017

This paper presents the results of an investigation into the effect of forced temperature change cycles on physical and mechanical properties of sand and weathered granite soil. The effect of forced temperature change cycles on the particle arrangement and the thermal conductivity was first investigated. A series of triaxial compression tests on the soils were also performed to look into the effect of temperature change cycles on the stress-strain-strength behavior.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.2
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• pp.397-407
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• 2013

Recently, a great progress has been made in bridge construction technology through the development of high performance materials and new structural types. However, most of attention has been paid to the cast-in-place technologies and material cost saving. The cast-in-place method is always subject to some environmental damages in construction sites, which frequently causes conflicts with residents. To overcome the disadvantages, a lot of fabrication construction method was developed. Most fabrication construction methods developed up to now have been applied for superstructure of bridges. In contrast, such fabricable methods developed for substructures are extremely rare. A fabricated column using ICH CFT(Internally Confined Hollow CFT) column was developed in a series of previous researches. Included in the previous studies are design and construction methods for the precast segmental coping, the column-coping connection, the column-segment connection, column-foundation connection. In this paper, seismic performance of the fabricated ICH CFT columns was extensively investigated experimentally. Two test specimens were prepared depending on the connection methods of segments; one by mortar-grouting method and the other by reinforcement method using stiffeners.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.15-20
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• 2019

This paper evaluated the construction costs of 11 design cases to decrease the horizontal forces applied to the abutment. They include two abutment types, which are to improve backfill materials for a reversed T-shaped abutment and geosynthetic Reinforced Abutment for Railways (RAR). The first type of economic analysis was that the internal friction angles of backfill materials were increased from Φ=35° to Φ=40° and 50° for a reversed T-shaped abutment. In addition, the second type was the cases with the design of geosynthetic RAR. When friction angles of 40° or 50° were applied through the improvement of the backfill material, the decrease in construction cost of the abutment was not large (2.0~3.9%), even though the horizontal forces applied to the abutment had decreased to 18~48%. In the case of applying the RAR, however, a maximum 30% cost reduction was evaluated by the decrease in horizontal force to "0" theoretically. The cost reduction resulted from the decrease in wall thickness, base slab size, and number and material change of pile foundation for the abutment.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.347-355
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• 2021

During the earthquake, for multi-story structure, if the first floor is soft, the deformation will concentrate on that floor causing a serious damage to the column members which might leads to the collapse of the whole structure like Piloti structure during the Pohang earthquake in Korea. According to the 2016 National Disaster Management Research Institute's "Investigation of Seismic Reinforcement and Cost Analysis of Domestic Non-seismic Buildings", the rate of seismic resistance of private reinforced concrete buildings was 38.3 %. Among them, it was reported that the seismic-resistance ratio of the two to five-story structures was less than 50 %. Accordingly, the government is trying to improve the seismic rate through support projects, but the conventional seismic reinforcement methods are still expensive, and emergency construction is difficult. Therefore, in this study, the field applicability was evaluated by improving the reinforcement method using Velcro, which was developed through the research project of the Ministry of Land, Transport and Maritime Affairs in 2014. In order to improve the performance of the Velcro reinforcement method, introducing the initial tension of Velcro using high foaming rigid urethane filling between the Velcro and concrete of the columns was applied. Additionally, an experiment was conducted to evaluate the ductility of Velcro specimen from the concrete confinement effect. As a result, the ductility of the Velcro specimen was improved compare to Normal specimen. However, the energy dissipation capacity of VELCRO2 is better than VELCRO1, yet the maximum ductility of those two specimens did not show a significant difference. Therefore, the improvement of the internal filler material is still needed to have a better maximum ductility.

• Journal of the Korean Geosynthetics Society
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• v.17 no.1
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• pp.119-126
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• 2018

The ground cavity occurring in the downtown area is on the increase. However, when ground subsidence is occurred or a cavity that causes it to occur is found, time and economic difficulties are follwed in recovery. In advance, this study conducted to develop filling system for reinforcement material which is consist of polymer pouch and admixture as a new filler material. We developed a polymer pouch that is water soluble in the precedent study. Since the filling system is trenchless method and don't need any plant, it has time and economic benefits. This system uses air pressure to filling out cavity in a short time. We estimate this system with respect to filling speed and filling ratio by model experiment. In addition, we could confirm various filling condition using DEM Analysis. So, we could develop filling system and analysis it.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.183-190
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• 2006

From the result of this research above, it may be summed up as follows. As a summary of results from each experiment, as the test body reinforced with the carbon rods was embedded inside the concrete section and made it possible uniform movement, this study has shown that it had excellent characteristics in improving the flexural strength and ductility. Also, it was considered as the carbon-steel sheet composite plate was to exert the strength more if it would complement the adherence with the concrete.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.735-744
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• 2007

This study deals with literature review, developing a predicting equation for the ultimate stress of prestressing (PS) CFRP, and experimental test with the parameters affecting the ultimate stress of prestressing CFRF in prestressed concrete beams strengthened by external prestressing. The ACI (American Concrete Institute) predicting equation for the ultimate stress of unbonded prestressing CFRP is analyzed to develop a new integrated predicting equation. The proposed predicting equation takes rationally the effect of internal PS steel into consideration as a function of prestressing tendon depth to neutral depth ratio. In the experimental study, prestressed concrete beams strengthened using external prestressing CFRP are tested with the test parameters having a large effect on the ultimate stress of prestressing CFRP. The test parameters includes infernal prestressing steel and external prestressing CFRP tendon reinforcement ratios, and span to depth ratio. The test results are analyzed to confirm the rationality and applicability of the proposed equation for predicting the ultimate stress of external prestressing CFRP.