• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.85-91
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• 1996

원전 증기발생기 시제 전열관으로 제조된 Alloy 600 및 690 에 대하여 ASTM 규정 (B163-86a)에 따라 확관실험을 실시하여 평가하였으며, 관 요소에 작용하는 응력을 해석하였다. 실험 결과 시제 전열관은 ASTM에서 요구하는 확관율 30% 및 그 이상의 35% 까지 확관할 경우에도 양호한 확관상태를 보였다. 확관에 따른 유동곡선의 축력은 Alloy 690 이 Alloy 600 에 비해 높았으며, 확관율의 증가에 따라 차이가 점진적으로 크지는 경향을 보였다. 얇은 벽 튜브의 확관에 대한 응력 해석식은 Modified Tresca's Yield Criterion를 도입하여 얻었으며, 소성변형식을 이용하여 확관율에 따른 응력을 예측하였다. 유동곡선의 이론 계산치와 실험치를 비교한 결과 Alloy 600의 경우 이론치는 실험치보다 약간 낮은 값으로 잘 일치되었으나, Alloy 690 경우는 Alloy 600에 비하여 확관율의 증가에 따라 차이가 커지는 경향을 보였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.310-313
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• 2010

본 논문에서는 등가소성힌지길이 개념을 새롭게 개선하여 도입함하여 구조물의 거동특성을 평가하는 프로그램을 개발하였다. 시간의 경과 및 외부환경 변화와 더불어 발생 가능한 지하구조물의 변상은 해당 구조물의 구성재료 및 작용하는 외압의 형태 등에 의해 다르게 나타나게 된다. 즉, 장기적인 지반외력의 변화에 의해 콘크리트 구조체의 천단부에 큰 휨압축응력과 인장을력이 생기는데, 내측에는 압축이 생기고 외측에는 인장균열이 발생한다. 또한 측벽이나 어깨부에서는 인장응력과 전단응력에 의한 균열이 발생하기도 한다. 따라서 개발된 프로그램으로 균열발생단면에 대하여 축력, 휨모멘트, 균열폭을 서로 연관 지을 수 있게 될 뿐만 아니라 균열폭의 확장을 추적해 나갈 수 있다. 해석기법을 토대로 개발된 해석모듈을 이용하여, 본 해석 기법의 타당성에 대한 검증을 실시하였다. 검증을 위해서는 수평보구조와 터널구조에 대해 각각 해석을 수행하였다. 그 결과, 구조물 내에서의 균열의 진전이 점차적으로 확장되어 가는 것이 표현 가능한 것을 확인하였으며, 해석결과의 타당성을 확인하였다.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.171-179
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• 1997

The high-tension bolted joints are clamped by the axial force which approaches the yielding strength. The introduced axial force is transmitted to the connection members pass through washer. The transferred load in connections is balanced to the compressive stress of plates, axial force in bolts and the external loads. In this mechanism, the compressive stress and slip load we dominated by the effective stiffness of bolted joints and plates. In general the effective stiffness is specified to product to the effective area and elasticity modulus in connections. In this reason, the conic projection formular which is assumed that the axial force in bolts is distributed to the cone shape and that region is related to the elastic deformation mechanism in connections, was proposed. But it conclude what kind of formula is justified. Therefore in this paper, the fatigue tests are performed to the high tension bolted joints and inspected to the phase on the friction face. And using the FEM and numerical method, it is analyzed and approximated to the compressive stress distribution and its region. Moreover, it is estimated to the effective area and to the relation the friction area to the effective compressive distribution region.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.81-92
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• 2010

In design of steel frames, it is generally believed that elastic system buckling analysis cannot predict real behaviors of structures, while inelastic system buckling analysis can give informative buckling behaviors of individual members considering inelastic material behavior. However, the use of Euler buckling equation with these system buckling analyses have the inherent problem that the methods evaluate unexpectedly large effective lengths of members having relatively small axial forces. This paper proposes a new method of obtaining elastic and inelastic effective lengths of all members in steel frames. Considering a fictitious axial force factor for each story of frames, the proposed method determines the effective lengths using the inelastic stiffness reduction factor and the iterative eigenvalue analysis. In order to verify the validity of the proposed method, the effective lengths of example frames by the proposed method were compared to those of previously established methods. As a result, the proposed method gives reasonable effective lengths of all members in steel frames. The effect of inelastic material behavior on the effective lengths of members was also discussed.

• Journal of Korean Society of Steel Construction
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• v.16 no.6 s.73
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• pp.737-745
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• 2004

In general, most of the beam-to-column connections for steel structures are regarded as either rigid connections or pin connections. Recently, the concept of a semi-rigid connection was introduced for a correct analysis of steel structures. Several experimental and theoretical researches have been performed regarding the structural behaviors of frames and buildings with semi-rigid connections. The results are not well known, and structural frame/building has not been designed to introduce the concept of semi-rigid connections between a beam and column until this time. To resolve this, this research depends on design specifications prepared by other advanced countries for the design of buildings with semi-rigid connections. Such a specification, however, should incorporate domestic characteristics of steel material properties and load conditions. This paper deals with structural capacities and deformable behaviors for a split-T tensile connection with F10T high-strength bolts to investigate the structural characteristics of semi-rigid frames. The experimental parameters include the thickness of T-flanges, painted or not, preloaded or not, and load pushover pattern. A total of 20 specimens were fabricated and tested with a 300-ton UTM. The structural capacities and behavior for split-T tensile connections were evaluated on each research parameter.

• Journal of Korean Society of Steel Construction
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• v.29 no.2
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• pp.99-110
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• 2017

This paper presents the study of the bending behavior of mooring chain links for keeping the position of the offshore floating structures. In general, chain links have been thought as the axial members due to the fundamental boundary condition. But, the flexural stiffness can be induced to the contact surface between chain links when friction occurs at the surface of the chain links due to high tensile force. Especially, the mooring chains for offshore floating platforms are highly tensioned. If the floater suffers rotational motion and the mooring chain links are highly tensioned, the rotation between contact links, induced by the floater rotation, generates the bending moment and relevant stresses due to the unexpected bending stiffness. In 2005, the mooring chain links for the Girassol Buoy Platform were failed after just 5 months after facility installation, and the accident investigation research concluded the chain failure was mainly caused by the fatigue due to the unexpected bending stress fluctuation. This study investigates the pattern of the induced bending stiffness and stresses of the highly tensioned chain links by nonlinear finite element analysis.

• Journal of Korean Society of Steel Construction
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• v.12 no.3 s.46
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• pp.259-268
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• 2000

In the friction-type joints the external applied load is transmitted by frictional force acting on the contact area of the plates fastened by the high strength bolts. This frictional force is proportional to the product of the bolt clamping force and slip coefficient of the faying surface. But the bolt clamping force is dependent on many factors when the turn-of-nut method is used. The preserved thread length and length-to-diameter ratios are one of the major factors governing the bolt clamping force. This paper presents the correct method of high strength bolt tightening through the experiment on the mechanical properties on sets of high strength bolts in accordance with preserved thread length and length-to-diameter ratios.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.91-100
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• 2019

Hollow prestressed concrete-filled steel tube (HCFT) piles, which combines PHC piles inside thin-wall steel tubes, were developed to increase the flexural strength of the pile with respect to the lateral load. Since P-M curves are needed for evaluating the structural safety of piles when applying HCFT piles to fields, equations for plotting P-M curves of HCFT piles in limit states were proposed. When the yield strength is applied to the steel tube and PC steel bar of HCFT piles, the proposed equations significantly underestimated the flexural strength of HCFT piles. Unlike the flexural strength test results, the proposed equations also provide greater flexural strengths for 12 mm thick steel pipe piles with the same diameter than for HCFT piles. However, when the ultimate strengths are used instead of the yield strengths for the steel tube and PC steel bar, the proposed equations provide the flexural strengths very close to the flexural strength test results.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2474-2480
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• 2013

A stress ribbon pedestrian bridge is the structure in which the axial force of prestressed deck, which is developed by introducing prestressed force into the thin deck with the very low value of span to deck-depth ratio which is installed on bearing cables with the specified sag, resists most of external loadings. Since the design of stress ribbon pedestrian bridges should be conducted by assuming the cross-section of deck, the area of bearing cables and post-tensioning cables, and the prestressed force of post-tensioning cables, it requires much more iterative processes than the design of general bridges. In this research, to minimize such iteration processes, regression equations which can reasonably assume the area of bearing cables and post-tensioning cables, and the prestressed force of post-tensioning cables, are suggested for the bridge length of 80m with the sag-span ratios of 1/30, 1/40, and 1/50.

• Journal of Korean Society of Steel Construction
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• v.20 no.3
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• pp.389-398
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• 2008

The current design practice of electric transmission tower is based on the allowable stress design. However, it is difficult to find the cause behind a transmission tower's collapse by the above design approach as the collapse is caused by large secondary deformations based on and geometrical nonlinear behavior.influence factor for the nonlinear behavior is mainly residual stress, initial imperfection and end restraints on members. In this study, the necessity of the nonlinear analysis is examined through the comparison between elastic ana the nonlinear analysis, a new analytical method (equivalent nonlinear analysis technique) is proposed. To confirm the reliability of the proposed method, the computed ultimate load of the transmission tower using the method was compared with that of the nonlinear finite element analysis. Effects of parameters, such as compressive force and the slenderness ratio of the brace member on the main post member, were investigated. The effective member length according to influential parameters was formulated in table form for practical purposes.