• 대한토목학회논문집
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• 제37권2호
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• pp.357-367
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• 2017

강지보로 보강된 터널 숏크리트 라이닝은 그 기하학적 형태로 인해 외부하중이 작용됨에 따라 휨 모멘트와 축력이 동시에 발생하게 된다. 숏크리트는 축력 수준에 따라 휨 강성이 달라지며, 이로 인한 심한 비선형 거동을 보인다. 또한 강지보 유형에 따라 역학적으로 상이한 지보 성능을 가진다. 본 연구에서는 화이버 단면 요소(fiber section element)를 이용해 압축력과 휨 모멘트를 동시에 받는 강지보-숏크리트 라이닝의 비선형합성거동을 평가할 수 있는 수치모델을 제시하였고, 이를 활용해 강지보 유형에 따른 합성지보 성능을 수치적으로 분석하였다. 또한, 지반-구조물 상호작용을 구현하기 위해 지반의 연화(softening) 거동을 고려하여 수정된 hyperbolic 모델을 제시하였다. 제시된 수치모델은 기존 아치형 실험체의 하중실험 결과와 해석결과를 비교하여 검증하였으며, 수치해석을 통해 강지보 유형에 따른 라이닝의 합성거동을 분석하였다. 해석결과를 통해, 복철근 형태의 강지보가 기존 H형강과 유사한 극한 하중 지지력을 가지는 것을 확인하였다. 또한 강재량 증가가 잔류 지지력 향상에 크게 기여하였으며, 지보재 주변의 지반강성이 증가함에 따라 강지보 유형에 따른 최대 하중지지력 개선 효과는 작아짐을 확인하였다.

• Steel and Composite Structures
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• 제18권1호
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• pp.213-233
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• 2015

A nonlinear finite element analysis (FEA) model is presented for simulating the behaviour of recycled aggregate concrete-filled steel tube (RACFST) beam-columns subjected to constant axial compressive load and cyclically increasing flexural loading. The FEA model was developed based on ABAQUS software package and a displacement-based approach was used. The proposed engineering stress versus engineering strain relationship of core concrete with the effect of recycled coarse aggregate (RCA) replacement ratio was adopted in the FEA model. The predicted results of the FEA model were compared with the experimental results of several RACFST as well as the corresponding concrete-filled steel tube (CFST) beam-columns under cyclic loading reported in the literature. The comparison results indicated that the proposed FEA model was capable of predicting the load versus deformation relationship, lateral bearing capacity and failure pattern of RACFST beam-columns with an acceptable accuracy. A parametric study was further carried out to investigate the effect of typical parameters on the mechanism of RACFST beam-columns subjected to cyclic loading.

• Steel and Composite Structures
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• 제23권5호
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• pp.517-527
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• 2017

In this paper, the effect of active confinement on the compressive behaviour of circular steel tube-confined concrete (STCC) and concrete-filled steel tube (CFST) columns is investigated. In STCC columns the axial load is only applied to the concrete core, while in CFST columns the load is carried by the whole composite section. A new method is introduced to apply confining pressure on fresh concrete by laterally prestressing steel tubes. In order to achieve different prestressing levels, short-term and long-term pressures are applied to the fresh concrete. Three groups of STCC and CFST specimens (passive, S-active and L-active groups) are tested under axial loads. The results including stress-strain relationships of composite column components, secant modulus of elasticity, and volumetric strain are presented and discussed. Based on the elastic-plastic theory, the behaviour of the steel tube is also analyzed during elastic, yielding, and strain hardening stages. The results show that using the proposed prestressing method can considerably improve the compressive behaviour of both STCC and CFST specimens, while increasing the prestressing level has insignificant effects. By applying prestressing, the linear range in the stress-strain curve of STCC specimens increases by almost twice as much, while the improvement is negligible in CFST specimens.

• 한국강구조학회 논문집
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• 제22권2호
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• pp.185-195
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• 2010

본 연구에서는 탄소섬유쉬트로 추가구속된 각형 CFT기둥 실험체의 단조압축실험을 수행하였고 이를 토대로 실험체의 연성능력을 평가하였다. 실험변수는 탄소섬유쉬트 보강겹수와 폭-두께비, 갭부착유무이며 실험변수에 따라 총 9개의 실험체를 제작하여 단조압축실험을 수행하였다. 실험을 통하여 각 실험체의 파괴거동, 하중-축변위 곡선, 최대내력, 변형성능을 비교한다. 탄소섬유쉬트의 추가구속은 기둥의 국부좌굴을 지연시켰으며 갭의 부착으로 탄소섬유쉬트의 구속분담시점을 지연시켜 연성능력은 상승한 것으로 나타났다.

• Computers and Concrete
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• 제15권1호
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• pp.1-20
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• 2015

Many existing reinforced concrete (RC) columns in structures tend to become substandard RC ones due to updated standards or environmental changes. These substandard columns may alter the behaviors of the whole structure and therefore are in urgent need of seismic retrofitting. Owing to their superior advantages, carbon fiber reinforced polymer (CFRP) composites are widely used to retrofit RC columns. The applications mainly focus on various substandard RC columns, but few deals with substandard columns with deteriorated concrete, especially damaged by earthquake. The purpose of this paper is to investigate the seismic behaviors of CFRP reinforced partially deteriorated RC columns and to evaluate the effect of CFRP sheets on them. Six flexure-dominant columns were tested under a constant axial load and transverse cyclic displacements. It is found that the seismic behaviors of partially deteriorated columns can be recovered by wrapping CFRP sheets on them. Numerical analysis is then conducted using finite element methods and verified with experimental results. The effects of the axial load ratio, the ratio of the thickness of CFRP sheet to the column diameter, and the slenderness ratio on the seismic behaviors of CFRP reinforced RC columns are evaluated. Finally, a method is proposed to determine the required thickness of CFRP sheet.

• Steel and Composite Structures
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• 제18권3호
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• pp.739-756
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• 2015

This paper presents investigations on the hysteretic behavior of concrete-filled circular tubular (CFCT) T-joints subjected to axial cyclic loading at brace end. In the experimental study, four specimens are fabricated and tested. The chord members of the tested specimens are filled with concrete along their full length and the braces are hollow section. Failure modes and load-displacement hysteretic curves of all the specimens obtained from experimental tests are given and discussed. Some indicators, in terms of stiffness deterioration, strength deterioration, ductility and energy dissipation, are analyzed to assess the seismic performance of CFCT joints. Test results indicate that the failures are primarily caused by crack cutting through the chord wall, convex deformation on the chord surface near brace/chord intersection and crushing of the core concrete. Hysteretic curves of all the specimens are plump, and no obvious pinching phenomenon is found. The energy dissipation result shows that the inelastic deformation is the main energy dissipation mechanism. It is also found from experimental results that the CFCT joints show clear and steady stiffness deterioration with the increase of displacement after yielding. However, all the specimens do not perform significant strength deterioration before failure. The effect of joint geometric parameters ${\beta}$ and ${\gamma}$ of the four specimens on hysteretic performance is also discussed.

• 한국항해항만학회지
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• 제29권6호
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• pp.515-522
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• 2005

선체를 구성하는 판부재는 일반적으로 면내하중과 횡하중의 조합하중이 작용하게 된다. 면내하중으로서는 주로 전체적인 선체거더의 휨과 비틀림에 의한 압축하중 및 전단하중이 있다. 횡하중은 수압과 화물압력에 의해서 작용하게 된다. 이러한 하중의 요소들은 항상 동시에 작용하는 것이 아니지만 한 개 이상의 하중이 존재하고 상호작용하게 된다. 그러므로, 좀더 합리적이고 안정적인 선박구조의 설계를 위해서는 이러한 조합하중이 선체판에 작응할 경우에 발생하게 되는 좌굴 및 최종강도거동의 상호관계를 좀더 자세히 분석할 필요가 있다. 실제로 선체판은 슬래밍과 팬팅과 같은 충격하중을 제외하고는 상대적으로 적은 수압이 작용하게 된다. 본 연구논문에서는 조합하중을 받는 선체판부재의 거동에 있어서 최종한계상태설계법에 기반을 둔 탄소성대변형 유한요소해석을 수행하였다. 본 연구에서는 압축하중과 횡하중이 판부재에 작용하였을 경우 횡하중의 크기에 따른 영향을 탄소성대변형 유한요소해석(ANSYS)을 수행하여 분석하였다.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2005년도 춘계학술대회 논문집
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• pp.61-67
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• 2005

선체를 구성하는 판부재는 일반적으로 면내하중과 횡하중의 조합하중이 작용하게 된다. 면내하중으로서는 주로 전체적인 선체거더의 휨과 비틀림에 의한 압축하중 및 전단하중이 있다. 횡하중은 수압과 화물압력에 의해서 작용하게 된다. 이러한 하중의 요소들은 항상 동시에 작용하는 것이 아니지만 한 개 이상의 하중이 존재하고 상호작용하게 된다. 그러므로, 좀더 합리적이고 안정적인 선박구조의 설계를 위해서는 이러한 조합하중이 선체판에 작용할 경우에 발생하게 되는 좌굴 및 최종강도거동의 상호관계를 좀더 자세히 분석할 필요가 있다. 실제로 선체판은 슬래밍과 팬팅과 같은 충격하중을 제외하고는 상대적으로 적은 수압이 작용하게 된다. 본 연구논문에서는 조합하중을 받는 선체판부재의 거동에 있어서 최종한계상태설계법에 기반을 둔 탄소성대변형 유한요소해석을 수행하였다. 본 연구에서는 압축하중과 횡하중이 판부재에 작용하였을 경우 횡하중의 크기에 따른 영향을 탄소성대변형 유한요소해석(ANSYS)을 수행하여 분석하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1994년도 봄 학술발표회 논문집
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• pp.199-208
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• 1994

One of the main objectives of the study is to propose a practical but realistic limit state model considering combined effect of axial and bending load for reliability analysis and safety assessment of cable-stayed bridge under vehicle traffic loads. This paper is intended to propose a new approach for the evaluation of reserved load carrying capacity of cable-stayed bridge under vehicle traffic loads in terms of equivalent strength, which may be defined as a bridge strength corresponding to the reliability index of the bridge. This can be derived from an inverse process based on the concept of FOSM form of reliability index. AFOSM and IST methods are used for the reliability analysis of the proposed models. The proposed reliability model and methods are applied to the safety assessment of Jindo Bridge which is one of major two cable-stayed bridges in Korea.

• Computers and Concrete
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• 제19권5호
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• pp.567-577
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• 2017

This study presents investigation of the behavior of moderately thick reinforced concrete slabs having hollow cores with different parameters. The experimental part of this investigation includes testing eight specimens of solid and hollow-core slab models having (2.05 m) length, (0.6 m) width and (25 cm) thickness under two monotonic line loads. Load versus deflection was recorded during test at mid span and under load. Numerically, the finite element method is used to study the behavior of these reinforced concrete slabs by using ANSYS computer program. The specimens of slab models are modeled by using (SOLID65) element to represent concrete slabs and (LINK180) element to represent the steel bars as discrete axial members between concrete nodes. The finite element analysis has showed good agreement with the experimental results with difference of (4.71%-8.68%) in ultimate loads. A parametric study have been carried out by using ANSYS program to investigate the effects of concrete compressive strength, size and shape of core, type of applied load and effect of removing top steel reinforcement.