• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 가을 학술발표회 논문집
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• pp.501-508
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• 2001

Free vibration analysis of multi-delaminated composite beam-columns subjected to axial compression load is performed in the present study. In order to investigate the effects of multi-delaminations on the natural frequency and elastic buckling load of multi-delaminated beam-columns, the general kinematic continuity conditions are derived from the assumption of constant slope and curvature at the multi-delamination tip. Characteristic equation of multi-delaminated beam-column is obtained by dividing the global multi-delaminated beam-columns into segments and by imposing recurrence relation from the continuity conditions on each sub-beam-column. The natural frequency and elastic buckling load of multi-delaminated beam-columns according to the incremental load of axial compression, which is limited to the maximum elastic buckling load of sound laminated beam-column, are obtained. It is found that the sizes, locations and numbers of multi-delaminations have significant effect on natural frequency and elastic buckling load, especially the latter ones.

• 한국공간구조학회논문집
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• 제23권1호
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• pp.69-76
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• 2023

A timber lattice roof, which has around 30m span, was constructed. In order to figure out the realistic buckling load level, the structural analysis of this roof structure was performed especially by stiffness of connection with various asymmetric snow load. Due to the characteristics of application of snow load, the load combinations of snow should be considered not only global area but also local part so that the critical buckling load could be observed as easy as possible. Geometrical imperfection was simulated to consider inaccurate shape of structure. And then nonlinear analysis were performed. Finally, this paper could investigate that the asymmetric snow load with the lower level stiffness of connection decreased the level of buckling load significantly.

• Steel and Composite Structures
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• 제34권4호
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• pp.547-559
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• 2020

Buckling restrained braces (BRBs) were developed as an enhanced alternative to conventional braces by restraining their global buckling, thus allowing development of a stable quasi-symmetric hysteretic response. A wider adoption of buckling restrained braced frames is precluded due to proprietary character of most BRBs and the code requirement for experimental qualification. To overcome these problems, BRBs with capacities corresponding to typical steel multi-storey buildings in Romania were developed and experimentally tested in view of prequalification. The first part of this paper presents the results of the experimental program which included sub-assemblage tests on ten full-scale BRBs and uniaxial tests on components materials (steel and concrete). Two different solutions of the core were investigated: milled from a plate and fabricated from a square steel profile. The strength of the buckling restraining mechanism was also investigated. The influence of gravity loading on the unsymmetrical deformations in the two plastic segments of the core was assessed, and the response of the bolted connections was evaluated. The cyclic response of BRBs was evaluated with respect to a set of performance parameters, and recommendations for design were given.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.223-227
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• 2004

The pultruded structural shapes are usually composed of thin-walled plate elements. Because the composite material has relatively low elastic moduli, the design of pultruded compression members may not be governed by the material strength limit state but by the stability limit state such as the local buckling or the global buckling. Therefore, the stability limit state must be checked to design pultruded columns. In this research, the local buckling analysis of pultruded I-shape column was conducted for various composite materials using the closed-form solution. To establish the design guidelines for the local buckling of pultruded I-shape compression members, the simplified form of equation to find the local buckling coefficient of pultruded I-shape column was proposed as a function of mechanical properties and the width ratio of plate components using the results obtainde by the closed-form solution. In order to verify the validity of proposed solution, the results obtained by the proposed approximate solution were compared with those of the closed-form solution and the experimental results.

• Structural Engineering and Mechanics
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• 제40권6호
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• pp.783-800
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• 2011

This paper addresses the finite strip formulations for the stability analysis of viscoelastic composite plates with variable thickness in the transverse direction, which are subjected to in-plane forces. While the finite strip method is fairly well-known in the buckling analysis, hitherto its direct application to the buckling of viscoelastic composite plates with variable thickness has not been investigated. The equations governing the stiffness and the geometry matrices of the composite plate are solved in the time domain using both the higher-order shear deformation theory and the method of effective moduli. These matrices are then assembled so that the global stiffness and geometry matrices of a moderately thick rectangular plate are formed which lead to an eigenvalue problem that is solved to determine the magnitude of critical buckling load for the viscoelastic plate. The accuracy of the proposed model is verified against the results which have been reported elsewhere whilst a comprehensive parametric study is presented to show the effects of viscoelasticity parameters, boundary conditions as well as combined bending and compression loads on the critical buckling load of thin and moderately thick viscoelastic composite plates.

• 한국항공우주학회지
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• 제33권4호
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• pp.35-40
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• 2005

압축하중을 받는 실린더형 구조물에 대한 보강방법으로는 스킨-스트링거, 격자보강 형상 등 여러 종류가 있다. 그 중 isogrid 형상은 정삼각형형태의 보강대가 반복되는 보강구조로서 여러 가지 조합하중 및 집중하중에 대한 대처능력이 우수한 보강구조이다.본 논문에서는 격자보강 구조 중 isogrid 구조에 대한 압축 좌굴시험 및 비선형 해석을 수행하였다. Isogrid 패널은 두께가 11.43 mm, 높이가 660 mm, 외경이 2.4 m이며 70도의 원호를 이루는 알루미늄합금 일체형 구조이다. 시편에 대한 압축 좌굴시험을 통하여 국부좌굴강도, 전체좌굴강도, 국부좌굴후의 거동 등을 확인하였다. 또한 MSC/MARC를 이용한 비선형 FEM 해석을 수행하여 구조시험 결과와 비교하였다. 해석 시에는 패널의 소성 가공 시 발생한 형상공차를 고려하였다. 시험결과와 해석결과는 좌굴하중 및 좌굴모드가 모두 비교적 일치하였다.

• 한국항공우주학회지
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• 제38권5호
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• pp.421-426
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• 2010

본 논문에서는 코너에서 대각선방향으로 인장하중을 받고 있는 접힌자국이 있는 사각형 멤브레인에서 두께가 주름 거동에 미치는 영향을 기하학적 비선형 후좌굴 유한요소해석을 통하여 연구하였다. 멤브레인은 쉘 요소로 모델링 하였고 좌굴을 발생시키기 위하여 면외방향으로 미소의 무작위성 기하학적 결함을 메쉬에 가하였다. 해석은 접히지 않은 원멤브레인과 수직방향으로 접힌 멤브레인에 대해 수행하였고 그 결과를 비교하였다. 해석결과 멤브레인의 두께가 감소함에 따라 주름의 발생과 성장을 크게 촉진함을 알 수 있었다. 또한 접힌 자국의 초기 전개각이 증가할수록 국부주름의 낮은 하중에서 발생하였으나 전역주름으로의 성장은 지연되는 경향을 보였다.

• 한국항공우주학회지
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• 제36권9호
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• pp.851-858
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• 2008

본 논문에서는 수직방향으로 접은 사각형 멤브레인의 주름 거동을 기하학적 비선형 후좌굴 해석을 사용하여 연구하였다. 멤브레인은 쉘 요소로 모델링 하였고 하중은 멤브레인의 코너에서 대각선 방향으로 가하였다. 해석에는 다양한 각도의 초기 전개각을 가지는 멤브레인을 고려하였고 접힌 자국이 없는 경우에 대해서도 해석을 수행하여 그 결과를 비교하였다. 해석결과 주름은 큰 코너하중이 가해진 지역에서 국부적으로 발생하였는데, 이 국부 주름은 하중 비의 증가에 따라 점차 성장하여 전역 주름으로 발전하였다. 또한 주름의 발생 및 성장 거동은 접힌 자국의 초기 전개각에 좌우되는 경향을 보였다.

• Steel and Composite Structures
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• 제46권3호
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• pp.417-433
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• 2023

The maximum ductility and cumulative ductility of connection joints of Buckling-Restrained Braced Frames (BRBF) are critical to the structural overall performance, which should be matched with the BRB ductility. The two-story and one-span BRBF with a one-third scale was tested under cyclic quasi-static loading, and the top-flange beam splice (TFBS) rotational connections were proposed and adopted in BRBF. The deformation capacity of TFBS connections was observed during the test, and the relationship between structural global ductility and local connection ductility was studied. The rotational capacity of the beam-column connections and the stability performance of the BRBs are highly relevant to the structural overall performance. The hysteretic curves of BRBF are stable and full under large displacement demand imposed up to 2% story drift, and energy is dissipated as the large plastic deformation developed in the structural components. The BRBs acted as fuses and yielded first, and the cumulative plastic ductility (CPD) of BRBs is 972.6 of the second floor and 439.7 of the first floor, indicating the excellent energy dissipation capacity of BRBs. Structural members with good local ductility ensure the large global ductility of BRBF. The ductile capacity and hysteretic behavior of BRBF with TFBS connections were compared with those of BRBF with Reduced Beam Section (RBS) connections in terms of the experimental results.

• 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.