• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.30-36
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• 2018

Researches on strengthening and rehabilitation are important since structural capacity is degraded by deterioration or damage of structural members. An effective strengthening scheme such as an externally bonded Carbon Fiber Reinforced Polymers (CFRP) can improve the structural performance of a concrete structure in a cost-effective way. Therefore, many experimental studies on strengthening methods have been widely carried out. In regards to the shear strengthening of a concrete beam, variables of the experimental studies were the amount of CFRP, the angle of the strip, the width of the strip, and the interaction between the materials. However, there are insufficient researches on bi-directional CFRP layout compared to the previous researches. In this study, a total of ten concrete beams were designed and tested to evaluate the shear strengthening effect using CFRP strips. The effectiveness of strengthening was investigated based on the shear contribution of materials, strain distribution of stirrup, and the maximum shear capacity of specimens.

• Journal of the Korean Geotechnical Society
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• v.23 no.5
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• pp.5-14
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• 2007

The purpose of this study is to evaluate the normalized behaviors of existing bridge foundations reinforced by micropiles. In order to do numerical method a finite element program was used to predict the micropile behavior and quantify their reinforcing effects on existing bridge foundations. In addition, the installation effects of battered micropiles on existing foundations were compared with vertically reinforced bridge foundations. Based on the study performed, it was found that the use of battered micropiles more efficiently reduces displacement of existing foundations than vertically installed micropiles under vertical and horizontal loadings, respectively. The batter angle of micropiles was also found to be most effective at about $15^{\circ}{\sim}20^{\circ}$ in reducing the vertical displacement. The horizontal reinforcing effect continues to be larger with an increase in batter angles. So, it is believed that the results presented could give an idea to enhance In-service performance of existing bridge foundations reinforced by micropiles.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.4
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• pp.141-148
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• 2008

In the recent construction industry, Carbon Fiber Reinforced Polymers(CFRPs) have been highly considered as innovative strengthening materials for civil structures due to their superior material properties. This paper is to offer design data and strengthening efficiency of reinforced concrete beams strengthened with CFRP Plate. Static tests were carried out to evaluate failure modes and strengthening capacity. Displacements and strains of steel and CFRP plates were obtained and analyzed through a series of fatigue tests. Also, Those evaluated the energy dissipation. Results of the tests showed increase in strengthening ratios caused debonding failure at the end of beams. For the beams wrapped with CFRP sheets around the end of the plates, debonding failure mode that was induced from flexural cracks was indicated. Through the fatigue tests, it was observed that displacements, strains of steel and CFRP plates converged into certain values. It is also proved that the beams strengthened with CFRP plates are able to resist fatigue loading under serviceability.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.553-556
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• 2009

최근 우리나라의 건설 분야에서는 생애주기비용(Life Cycle Cost;이하 LCC)/가치공학(Value Engineering; 이하 VE)을 적용한 구조물 설계가 실시되고 있다. 이는, 건설교통부에서 공공건설사업의 효율성을 제고하기 위하여 실시하고 있으며, 대통령령에 따라 "건설기술관리법시행령"을 제정하여 공공사업분 수행 절차와 기준을 법제화 하였으며 이후 시행령 38조 13의 "설계의 경제성등 검토" 실시를 의무화하는 시행지침을 작성하여 수행하고 있다. 이러한, LCC/VE의 검토에서 보수 보강 공사비 산정은 유지보수공사 프로파일링을 통한 보수 보강 시기를 산정(건설교통부, 2003)하여 교량 구성요소별 보수 교체 주기를 산정(건설교통부, 2001)에서 제시한 기간을 적용하여 LCC/VE를 평가하고 있다. 하지만, 이러한 보수 보강 공사비의 적용은 일괄적인 적용이며, 예전 국내의 교량 건설기술이 현재와 같이 발전된 상태에서의 현황이 아니므로 본 연구에서는 현재 고속국도에 완공되어 운용중인 교량 구조물을 시설물의 안전관리에 관한 특별법 시행령(2008)에 따른 "시설물의 안전점검 및 정밀안전진단 지침"에 의한 교량의 초기점검, 정밀점검 및 정밀안전진단 자료를 조사 분석하여 보수 보강 공사비 곡선을 추정하려 한다.

• Journal of Korean Society of Steel Construction
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• v.20 no.3
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• pp.445-454
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• 2008

Based on previous research on steel moment connections, experimental and analytical results showed that the deformation capacity was poor in specimens using RHS columns and with conventional weld access holes and strain concentration at the end of beam is influenced by the efficiency in transmitting the moment in the web of beam through the beam-to-column joint. This paper is focused on the retrofitting of pre-Kobe steel moment frame connections using a stiffened RBS and a welded horizontal stiffener. These retrofitting methods were considered only in beam bottom flange. A parametric study was performed using nonlinear finite element analysis to elucidate and improve the retrofit methods of connections.

• Journal of the Korean Geotechnical Society
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• v.16 no.4
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• pp.129-139
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• 2000

The liquefaction of reclaimed land generally caused the harbor facilities to hazards. In Korea, the major harbor quay walls are gravity type and the gravity quay wall is not a good earthquake resistant structure. Recently, various earthquake resistant quay walls have been suggested, but the study on the efficiency of reinforced quay wall was not much performed. In this study, numerical analysis is carried out for performance evaluation of easily adoptable earthquake resistant quay walls. The results of numerical analysis are compared with shaking table test that is performed at the same cross-section.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.13 no.2
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• pp.209-220
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• 2000

For non-linear analysis of stiffened shell structures, the total Lagrangian formulation is presented based upon the degenerated shell element. Geometrically correct formulation is developed by updating the direction of normal vectors and taking into account second order rotational terms in the incremental displacement field. Assumed strain concept is adopted in order to overcome shear locking phenomena and to eliminate spurious zero energy mode. The post-buckling behaviors of stiffened shell structures are traced by modeling the stiffener as a shell element and considering general transformation between the main structure and the stiffener at the connection node. Numerical examples to demonstrate the accuracy and the effectiveness of the proposed shell element are presented and compared with references' results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.102-110
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• 2006

This paper examines experimentally the ultimate behavior of I-type steel beam strengthened with external tendon and cylindrical anchorage and analyzes the strengthening effect on the parameters such as initial tendon force, eccentricity, number of strands, and strand areas. The experiment demonstrated that increasing the number of strands, strand areas and eccentricity is more effective than increasing initial tendon force. The proposed cylindrical anchorage system has advantages in applying these parameters. The results showed that the cylindrical anchorage system is efficient and applicable to strengthen steel beam.

• Journal of the KSME
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• v.31 no.3
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• pp.293-299
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• 1991

단섬유보강 금속복합재료의 2차가공은 금속복합재료의 넓은 범위 응용을 위해 필히 요구된다. 여러 가공방법 중 하나인 열간압출시 보강섬유파괴 및 계면에서의 접합분리 및 균열발생이 없는 제조공정의 최적화를 위해서 가공시 내부조직의 소성변형 기구 규명보다 압출력에 의한 응력분 포와 기지재료와 보강섬유 사이 계면 변화 및 기계적 특성 관계규명이 정량적으로 요구된다. 본 글에서는 유한요소법을 이용하여 계면에서의 접합상태를 임의로 가정하여 압출조건에 따른 압 출후의 보강섬유 방향 및 계면균열 및 접합분리를 거시적으로 예측하고, advanced shear-lag을 이용하여 균열 전, 후의 응력. 변형관계를 미시적으로 규명할 수 있음을 제시하였다. 그러나 향후 현상적 모델인 shear-lag 모델을 수학적 모델인 균질화법에 도입하면 미시적. 거시적 거 동해석이 함께 요구되는 금속복합재료의 열간압출거동 해석을 일체적으로 행할 수 있어 효율적 이고 정확한 예측이 가능하리라고 사료된다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2005.03a
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• pp.220-227
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• 2005

최근에 수행된 철골모멘트 접합부의 실험 및 해석결과에 의하면, 기둥으로 각형강관을 가진 접합부가 H형강을 기둥으로 사용하는 접합부에 실험체에 비해서 조기에 스캘럽 단부에서 취성파단이 발생하는 열등한 변형능력을 나타냈다. 이는 각형강관 기둥의 면외변형에 따른 보 웨브의 모멘트 전달효율의 저하, 스캘럽이 가지는 노치효과 및 합성보의 구속효과가 주요원인으로 밝혀졌다. 실험결과는 또한 개선된 수평스티프너로 하부 플랜지를 보강한 실험체는 우수한 변형능력을 가짐을 보였다. 본 연구에서는 이러한 영향을 고려하여, 다양한 수평스티프너로 보강된 접합부에 관한 유한요소해석을 실시하였다. 해석결과를 바탕으로 파일럿 테스트를 실시한 결과, 수평스티프너로 보강된 RBS 접합부 (SR)와 연장된 수평스티프너를 가진 접합부(LH)는 우수한 변형능력을 보였다.