• 한국강구조학회 논문집
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• 제27권1호
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• pp.119-129
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• 2015

강재량을 줄이면서도 풍하중의 영향을 완화시킬 수 있는 장점으로, 수평재로 서로 연결된 다수의 수직 원형강관으로 구성된 멀티기둥 풍력타워 시스템은 기존의 단일 실린더형 타워구조에 대한 대안으로 고려될 수 있다. 멀티기둥 타워를 하나의 타워구조로 거동하게 하기 위해서는 수직 강관과 수평 강관의 연결부인 강관조인트의 강도 확보가 중요하다. 본 연구에서는 멀티기둥에 적용될 수 있는 T 조인트의 강도평가를 수행하였다. AISC, Eurocode3, ISO 19902, CIDECT의 4가지 강관조인트 설계기준을 검토하고, 조인트에서 주강관과 지강관의 세장비에 대한 매개변수해석을 통하여 설계기준에서 제공되는 강도산정식의 타당성을 검토하였다.

• Steel and Composite Structures
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• 제3권5호
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• pp.321-331
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• 2003

The paper presents the results of an experimental investigation conducted on welded tubular joints, that are employed in offshore platforms, to study the behaviour and strength of these joints under axial brace compression loading. The geometrical configuration of the joints tested were T and Y. The nominal diameter of the chord and brace members of the joint were 324 and 219 mm respectively. The chord thickness was 12 mm and the brace 8 mm. The tested joints are approximately quarter size when compared to the largest joints in the platforms built in a shallow water depth of 80 m in the Bombay High field. Some of the joints were actually fabricated by a leading offshore agency which firm is directly involved in the fabrication of prototype structures. Strength of the internally ring-stiffened joints was found to be almost twice that of the unstiffened joints of the same configuration and dimensions. Bending of the chord as a whole was observed to be the predominant mode of deformation of the internally ring-stiffened joints in contrast to ovaling and punching shear of the unstiffened joints. It was observed in this investigation that unstiffened joint was stiffer in ovaling mode than in bending and that midspan deflection of unstiffened joint was insignificant when compared to that of the internally ring stiffened joint. The measured midspan deflection of the unstiffened joint in this investigation and its relation with the applied axial load compares very well with that predicted for the brace axial displacement by energy method published in the literature. A comparison of the measured deflection and ovaling of the unstiffened joint was made with that published by the author elsewhere in which numerical prediction of both quantities have been made using ANSYS software package. The agreement was found to be quite good.

• Steel and Composite Structures
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• 제4권2호
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• pp.149-167
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• 2004

Offshore platforms have to serve in harsh environments and hence are likely to be damaged due to wave induced fatigue and environmental corrosion. Welded tubular joints in offshore platforms are most vulnerable to fatigue damage. Such damages endanger the integrity of the structure. Therefore it is all the more essential to assess the capacity of damaged structure from the point of view of its safety. Eight internally ring stiffened fatigue damaged tubular joints with nominal chord and brace diameter of 324 mm and 219 mm respectively and thickness 12 mm and 8 mm respectively were tested under axial brace compression loading to evaluate the reserve capacity of the joints. These joints had earlier been tested under fatigue loading under corrosive environments of synthetic sea water and hence they have been cracked. The extent of the damage varied from 35 to 50 per cent. One stiffened joint was also tested under axial brace tension loading. The residual strength of fatigue damaged stiffened joint tested under tension loading was observed to be less than one fourth of that tested under compression loading. It was observed in this experimental investigation that in the damaged condition, the joints possessed an in-built load-transfer mechanism. A bi-linear stress-strain model was developed in this investigation to predict the reserve capacity of the joint. This model considered the strain hardening effect. Close agreement was observed between the experimental and predicted results. The paper presents in detail the experimental investigation and the development of the analytical model to predict the reserve capacity of internally ring stiffened joints.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1998년도 가을 학술발표회 논문집
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• pp.43-50
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• 1998

The current design equations for ultimate strength of tubular joints are based on a limited number of experimental results performed on simple joints with simple loading conditions and depend on value of the branch to the chord diameter- ratio $\beta$ too much. Therefore, the purpose of this study is to estimate the ultimate strength of CHS tilbular joints considering the effects of branch inclination angles $\theta$, chord length to diametel ratio $\alpha$ and chord end conditions by finite element analysis. The analyses are performed using finite element software ADINA that is capable of modeling elasto-plastic material behavior as well as geometric nonlinearities. The results show that the current use of sin $\theta$ in normalized design equations for inclined branches is reasonable, but somewhat conservative. When compared with the previous experimental database, the close numerical results are obtained from the parametric studies on the static strength of T-, Y-, DT- and X-joints. Also, a new design equation for ultimate stregth of CHS tubular joints is derived using a modified version of the ring model which can include the effects of $\alpha$ and chord end condtion.

• Structural Monitoring and Maintenance
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• 제4권3호
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• pp.255-268
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• 2017

Fibre reinforced polymers (FRP) are widely used to strengthen steel structures and retrofitting of existing structures due to its excellent properties. This paper reviews the use of carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) in strengthening steel and concrete structures. The paper discusses the use of FRP in strengthening of steel bridges, uses of FRP in repairing of corroded structures and the behaviour of different adhesives. The paper then deals with the FRP strengthened hollow sections and the different failure experienced. The paper then reviewed the current state of art used in strengthening tubular structures and focusing on FRP in strengthening of joints.

• Steel and Composite Structures
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• 제43권1호
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• pp.107-116
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• 2022

This paper presents results of numerical studies completed on unreinforced and doubler plate reinforced Elliptical Hollow Section (EHS) T-joints subjected to axial compressive loading on the brace member. Non-linear finite element (FE) models were developed using the finite element code, ABAQUS. Available test data in literature was used to validate the FE models. Subsequently, a parametric study was carried out to investigate the effects of various geometrical parameters of main members and reinforcement plates on the ultimate capacity of reinforced EHS T-joints. The parametric study found that the reinforcing plate significantly increases the ultimate capacity of EHS T-joints up to twice the capacity of the corresponding unreinforced joint. The thickness and length of the reinforcing plate have a positive effect on the ultimate capacity of Type 1 joints. This study, however, found that the capacity of Type 1 orientation is not dependent on the brace-to-chord diameter ratio. As for type 2 orientations, the thickness and length of the reinforcement have a minimal effect on the ultimate capacity. A new design method is introduced to predict the capacity of the reinforced EHS T-joints Type 1 and 2 based on the multiple linear regression analyses.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.207-214
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• 2003

The fatigue behaviour of six different hollow section T-joints subjected to out-of-plane bending moment was investigated experimentally using scaled steel models. The joints had circular brace members and rectangular chord members. Hot spot stresses and the stress concentration factors. (SCFs) were determined experimentally. Fatigue testing was carried out under constant amplitude loading in air. The test results have been statistically evaluated, and show that the experimental SCF values for circular-to-rectangular (CHS-to-RHS) hollow section joints were found to be below those of circular-to-circular (CHS-to-CHS) hollow section joints. The fatigue strength, referred to experimental hot spot stress, was in reasonably good agreement with referred fatigue design codes for tubular joints.

• Ocean Systems Engineering
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• 제8권4호
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• pp.409-426
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• 2018

This paper presents the strengthening of tubular joint by wrapping Carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP). In this study, total number of layers, stacking sequence and length of wrapping are the different parameters involved when fiber reinforced polymers (FRP) composites are used for strengthening. For this, parameters where varied and results were compared with the reference joint. The best stacking sequence was identified which has the highest value in ultimate load with lesser deflections. For determining the best stacking sequence, numerical investigation was performed on CFRP composites; length of wrapping and number of layers were fixed. Later, the studies were focused on CFRP and GFRP strengthened joint by varying the total number of layers and length of wrapping. An attempt was done to propose a parametric equation from multiple regression analysis, which can be used for CFRP strengthened joints. Hashin failure criteria was used to check the failure of composites. Results revealed that FRP was having a greater influence in the load bearing capacity of joints, and in reducing the deflections and stresses of joint under axial compressive loads. It was also seen that, CFRP was far better than GFRP in reducing the stresses and deflection.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2001년도 추계학술발표대회 개요집
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• pp.281-284
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• 2001

Fatigue behaviour of eight different hollow section T-joints was investigated experimentally using scaled steel models. The joints had circular brace members and rectangular chords (CRHS). Hot spot stresses and the stress concentration factors (SCFs) were determined experimentally. Fatigue testing was carried out under constant amplitude loading in air. The experimental SCF values for CRHS joints were found to be between those of circular-to-circular (CCHS) and rectangular-to-rectangular (RRHS) hollow section joints. The fatigue strength referred to experimental hot spot stress was in reasonably good agreement with current fatigue design codes for tubular joints.

• 한국강구조학회 논문집
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• 제13권1호
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• pp.9-18
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• 2001

대스팬 철골구조물의 지붕구조로서 강관트러스가 많이 사용되고 있다. 강관트러스는 타 단면(H, L형강 등)에 비하여 구조역학적인 측면에서 유리하다고 할 수 있다. 그러나 지관의 압축력에 의하여 격점부에는 국부좌굴이 발생하고 이로 인하여 구조체 전체의 내력이 격점부의 지배를 받게 된다. 또한 강관 격점부에서의 내력 및 변형 성상은 거동이 복잡하여 정확한 거동을 예측하기 어려울뿐만 아니라 해석적으로 정밀해를 구하기 어렵다. 이 연구에서는 T형 격점부를 대상으로 지관과 주관의 직경비(d/D) 주관경과 두께비(D/T)에 관한 변수를 설정하여 일련의 실험을 진행하고 기초하여 단순한 링해석법을 이용하여 항복하중에 관한 실용해를 제안하였다. 또한 부가적으로 각국에서 제안된 항복하중에 관한 기존의 연구결과와도 비교, 검토하였다.