• 한국안전학회지
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• 제35권3호
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• pp.6-15
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• 2020

This study examined the structural behaviors and ultimate loads of assembled system scaffolds by load tests. Considering the number of bay and bracing installation, four specimens were tested. The bays were divided into 1 bay and 2 bays, with and without the bracing member installed. Failure modes and horizontal displacements show that the whole column buckled without showing no point of inflection in the column, regardless of whether or not braces were installed. Thus, the current design method of selecting the vertical spacing between the horizontal members of the system scaffold as the effective buckling length underestimates the effective buckling length. In case of 1 bay specimens, the ultimate loads between specimens with and with bracing members are similar. However, in case of 2 bay specimens, the specimen with bracing members shows the increased ultimate load of 36% compared with that without bracing members. In addition, as the number of bays in the system scaffold increases, the ultimate load of the unit vertical column increases in case of the specimen with bracing installation. However, in the specimen without bracing members, the ultimate load of the unit column reduces with the increment of the number of bays due to the torsional buckling. Therefore, it is essential to install bracing members to increase the whole strength of system scaffolds and the ultimate load of the unit column.

• 대한기계학회논문집A
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• 제36권1호
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• pp.51-58
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• 2012

본 연구는 외부 수압을 받는 복합재 원통 셸에 대해서 원통 좌굴식 (ASME 2007,NASA SP- 8007)과 유한요소법을 이용하여 좌굴 압력을 예측하기 위함이다. 본 연구에 사용된 모델은 적층 각도 [0/90]$_{12t}$ 이며 복합재 재질은 USN 125 이다. 복합재는 프리프래그 방식으로 제작되었다. 본 논문에 사용된 연구 방법은 원통 셸의 좌굴식, 유한요소해석을 수행하고 이를 실험으로 검증 하였다. 원통 셸의 좌굴식과 유한요소 결과를 비교하기 위하여 $20^{\circ}{\sim}90^{\circ}$까지 $5^{\circ}$씩 변화시켜 도식화 하여 비교하였다. 유한요소해석의 결과는 선형과 비선형은 안전율 0.85~1.0 으로 잘 일치하였다. 좌굴 압력식은 적층각이 증가할수록 좌굴압력이 증가하였다. 유한요소 해석과 비교하면 ASME 2007 식이 NASA SP-8007 식보다 안전율이 더 큰 식임을 알 수 있었다.

• 한국강구조학회 논문집
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• 제23권6호
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• pp.679-690
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• 2011

판의 탄성좌굴에 관해서는 이미 많은 이론적 실험적 연구가 이루어져 여러 가지 경계조건 및 하중에 대해서 좌굴응력을 결정하는데 큰 어려움이 없다. 현재 플랜지 및 웨브판에 대한 설계기준도 휨에 대한 좌굴응력을 기준으로 하고 있으며, 후좌굴강도에 안전율을 적용하여 고려하도록 하고 있다. 그러므로 본 연구는 이상적인 조건하에서 전개되는 선형좌굴이론에서 뿐만이아니라, 유한처짐을 허용하는 극한강도 설계개념에 까지 확장되어진다. 또한, 이 개념에 근거한 실험적 연구가 이루어져 단순지지 조건을 만족시킬 수 있는 보강재에 대한 현 시방규정의 적정성을 분석 검토하고자 한다. 본 연구의 결과를 토대로 세장비의 변화에 따른 강상자형의 극한강도를 결정하는 식을 제시하고자 한다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.178-188
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• 2007

In this paper, a half-scaled substructure test was performed to evaluate the buckling and structural safety of an existing transmission tower subjected to wind load. A loading scheme was devised to reproduce the dead and wind loads of a prototype transmission tower, which uses a triangular jig that is mounted on the reduced model to which the similarity law of a half length was applied. As a result of the preliminary numerical analysis carried out to evaluate the stability of a specimen for the design load, it was confirmed that the calculated axial forces of tower leg members were distributed to $80{\sim}90%$ of an admissible buckling load. When the substructured transmission tower was loaded by 270% of its maximum admissible buckling load, it was failed due to the local buckling that is occurred in joints with weak constraints for out-of-plane behavior of leg members. By inspection of load-displacement curves, displacements and strains of members, it is considered that this local buckling was due to additional eccentric force by unbalanced deformation because the time that is reached to yielding stress due to the bending moment is different at each point of a same section.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
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• pp.129-139
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• 2005

The focused topic according to be slender and longer of cable stayed bridge's main span is as follows (1) Aerodynamic stability (2) Lateral movement of stiffening girder caused by wind force during and after construction (3) Global bucking of stiffening girder caused by axial force Among this, the number 3 has not received much attention in the past due to high buckling safety factor of stiffening girder. However, according to be slender of stiffening girder, the topic of buckling stability of girder is not any more unconcerned subject. The purpose of this paper is to examine the effect of stay cable's nonlinear behavior on the buckling stability of cable-stayed bridge.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2003년도 춘계학술발표회
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• pp.167-172
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• 2003

Place that have cutout inner bottom and girder and floor etc. in hull construction absence is used much, and this is strength in case must be situated, but establish in region that high stress interacts sometimes fatally in region that there is no big problem usually by purpose of weight reduction, a person and change of freight piping etc.. Because cutout's existence gnaws in this place, and, elastic buckling strength by load causes large effect in ultimate strength. Therefore, perforated plate elastic buckling strength and ultimate strength is one of important design criteria which must examine when decide structural elements size at early structure design step of ship. Therefore, and, reasonable elastic buckling strength about perforated plate need design ultimate strength. Calculated ultimate strength change several aspect ratioes and cutout's dimension. and thickness in this investigation. Used program applied ANSYS F.E.M code transformation finite element law that is mediocrity finite element analysis code.

• Structural Engineering and Mechanics
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• 제6권2호
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• pp.161-172
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• 1998

Reinforced concrete beams possess variable flexural and torsional stiffnesses due to formation of cracks in the tension area along the beam. In order to check the stability of the beam, it is thus more appropriate to divide the beam into a finite number of segments for which mean stiffnesses and also bending moments are calculated. The stability analysis is further simplified, by using these mean values for each segment. In this paper, an algorithm for calculating the critical lateral buckling slenderness ratio for a definite load level, in a reinforced concrete beam without lateral support at the flanges, is presented. By using this ratio, the lateral buckling safety level of a slender beam may be checked or estimated.

• Structural Engineering and Mechanics
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• 제26권6호
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• pp.673-685
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• 2007

Reinforced concrete beams can be strengthened in a structural retrofit process by attaching steel plates to their sides by bolting. Whilst bolting produces a confident degree of shear connection under conditions of either static or seismic overload, the plates are susceptible to local buckling. The aim of this paper is to investigate the local buckling of unilaterally-restrained plates with point supports in a generic fashion, but with particular emphasis on the provision of the restraints by bolts, and on the geometric configuration of these bolts on the buckling loads. A numerical procedure, which is based on the Rayleigh-Ritz method in conjunction with the technique of Lagrange multipliers, is developed to study the unilateral local buckling of rectangular plates bolted to the concrete with various arrangements of the pattern of bolting. A sufficient number of separable polynomials are used to define the flexural buckling displacements, while the restraint condition is modelled as a tensionless foundation using a penalty function approach to this form of mathematical contact problem. The additional constraint provided by the bolts is also modelled using Lagrange multipliers, providing an efficacious method of numerical analysis. Local buckling coefficients are determined for a range of bolting configurations, and these are compared with those developed elsewhere with simplifying assumptions. The interaction of the actions in bolted plates during buckling is also considered.

• Structural Engineering and Mechanics
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• 제48권3호
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• pp.367-382
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• 2013

Different types of long slender pile shall buckle with weak soil and liquefied stratum surrounded. Different from considering single side earth pressure, it was suggested that the lateral earth pressure can be divided into two categories while buckling: the earth pressure that prevent and promotes the lateral movement. Active and passive earth pressure calculation model was proposed supposing earth pressure changed linearly with displacement considering overlying load, shaft resistance, earth pressure at both sides of the pile. Critical buckling load calculation method was proposed based on the principle of minimum potential energy quoting the earth pressure calculation model. The calculation result was contrasted with the field test result of small diameter TC pile (Plastic Tube Cast-in-place pile). The fix form could be fixed-hinged in the actual calculation assuring the accuracy and certain safety factor. The contributions of pile fix form depend on the pile length for the same geological conditions. There exists critical friction value in specific geological conditions that the side friction has larger impact on the critical buckling load while it is less than the value and has less impact with larger value. The buckling load was not simply changed linearly with friction. The buckling load decreases with increased limit active displacement and the load tend to be constant with larger active displacement value; the critical buckling load will be the same for different fix form for the small values.

• Steel and Composite Structures
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• 제47권2호
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• pp.269-287
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• 2023

The WGJ420 fire-resistant weathering (FRW) steel is developed and manufactured with standard yield strength of 420 MPa at room temperature, which is expected to significantly enhance the performance of steel structures with excellent fire and corrosion resistances, strong seismic capacity, high strength and ductility, good resilience and robustness. In this paper, the mechanical properties of FRW steel plates and buckling behavior of columns are investigated through tests at elevated temperatures. The stress-strain curves, mechanical properties of FRW steel such as modulus of elasticity, proof strength, tensile strength, as well as corresponding reduction factors are obtained and discussed. The recommended constitutive model based on the Ramberg-Osgood relationship, as well as the relevant formulas for mechanical properties are proposed, which provide fundamental mechanical parameters and references. A total of 12 FRW steel welded I-section columns with different slenderness ratios and buckling load ratios are tested under standard fire to understand the global buckling behavior in-depth. The influences of boundary conditions on the buckling failure modes as well as the critical temperatures are also investigated. In addition, the temperature distributions at different sections/locations of the columns are obtained. It is found that the buckling deformation curve can be divided into four stages: initial expansion stage, stable stage, compression stage and failure stage. The fire test results concluded that the residual buckling capacities of FRW steel columns are substantially higher than the conventional steel columns at elevated temperatures. Furthermore, the numerical results show good agreement with the fire test results in terms of the critical temperature and maximum axial elongation. Finally, the critical temperatures between the numerical results and various code/standard curves (GB 51249, Eurocode 3, AS 4100, BS 5950 and AISC) are compared and verified both in the buckling resistance domain and in the temperature domain. It is demonstrated that the FRW steel columns have sufficient safety redundancy for fire resistance when they are designed according to current codes or standards.