• Structural Engineering and Mechanics
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• 제34권2호
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• pp.175-188
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• 2010

This paper deals with the buckling and postbuckling responses, and the progressive failure of square laminates of symmetric lay-up with a central rectangular cutout under in-plane shear load. A detailed investigation is made to show the effects of cutout size and cutout aspect ratio on the buckling and postbuckling responses, failure loads and failure characteristics of $(+45/-45/0/90)_{2s}$, $(+45/-45)_{4s}$ and $(0/90)_{4s}$ laminates. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. In addition, the effects of boundary conditions on buckling loads, failure loads, failure modes, and maximum transverse deflection for a $(+45/-45/0/90)_{2s}$ laminate with and without a square cutout have been presented. It is concluded that because of early onset of delamination at the net section of cutouts before first-ply failure, total strength of the laminate with very small cutouts can not be utilized.

• 한국강구조학회 논문집
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• 제21권1호
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• pp.71-81
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• 2009

본 연구에서는 지진에 대해 보강 효과가 뛰어난 비좌굴 가새를 바탕으로 필로티를 가진 중저층 집합주택에 적합한 비좌굴 knee brace에 대해 총 5개의 실험체를 제작하여 실험을 실시하였다. 이는 공간활용이 우수하고 동선이나 시야를 방해하지 않으며, 시공 방법 또한 간단하여 필로티 층을 가진 중저층 건물에 대해 유리하다는 장점을 가지고 있다. 각 실험체의 변수로는 중심코어의 크기, 외부 보강재의 크기, 단부의 크기 및 형태로 정하였으며 실험결과 중심코어의 크기가 가장 큰 영향을 미치는 것으로 나타났다. 외부 보강재의 크기는 중심코어의 크기에 비해 효과는 미비하나, 파괴거동이나 연성도 측면에서는 영향을 미치는 것으로 나타났다. 실험을 통해 얻어진 힘-변위 그래프는 인장과 압축에서 비교적 안정적인 이력거동을 보였으며 AISC 2005 Seismic Provision 규정에서 제시한 연성도와 에너지 소산능력 측면에서도 충분한 효과를 발휘하였다. 또한 설계 층간 변위비의 2배까지 가력을 실시하였을 때, 가새의 전체 좌굴이나 국부적인 좌굴이 일어나지 않아야 한다는 조항을 만족하는 것으로 나타났다.

• Steel and Composite Structures
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• 제45권6호
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• pp.907-929
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• 2022

Compression experiments were conducted to investigate the compressive behavior of built-up open-section columns consisting of four cold-formed steel channels (BOCCFSs) of different lengths, thicknesses, and cross-section sizes (OB90 and OB140). The load-displacement curves, failure modes, and maximum compression strength values were analyzed in detail. The tests showed that the failure modes of the OB90 specimens transformed from a large deformation concentration induced by local buckling to flexural buckling with the increase in the slenderness ratio. The failure modes of all OB140 specimens were deformation concentration, except for one long specimen, whose failure mode was flexural buckling. When the slenderness ratios of the specimens were less than 55, the failure modes were controlled by local buckling. Finite element models were built using ABAQUS software and validated to further analyze the mechanical behavior of the BOCCFSs. A parametric study was conducted and used to explore a wide design space. The numerical analysis results showed that when the screw spacing was between 150 mm and 450 mm, the difference in the maximum compression strength values of the specimens was less than 4%. The applicability and effectiveness of the design methods in Chinese GB50018-2002 and AISI-S100-2016 for calculating the compression strength values of the BOCCFSs were evaluated. The prediction methods based on the assumptions produced predictions of the strength that were between 33% to 10% conservative as compared to the tests and the finite element analysis.

• 대한안전경영과학회지
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• 제25권2호
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• pp.187-192
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• 2023

In piping systems, trapeze hangers are subjected to vertical and horizontal seismic loads and stiffeners are used. In this study, monotonic compression tests were conducted with the removable stiffeners using three variables: stiffener clamp fixing position, section length, and installation direction. The maximum load reinforced with stiffeners could withstand a compressive load of 11kN by applying a safety factor of 10%. It could be estimated that the fixing clamp spacing or the length of shape and load had a proportional relationship. And the stiffener must be fixed in the direction of the strong axis on hinge parts. Also the stiffener buckiling load design proposes to use a method of calculate the flexural buckling compressive strength of and unreinforced full threaded bolt.

• 한국강구조학회 논문집
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• 제26권3호
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• pp.169-176
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• 2014

본 연구에서는 콘크리트 충전 각형강관 (CFTP) 단주기둥에 CFRP 쉬트를 횡방향으로 보강하고 중심축하중 실험을 수행하였다. 실험변수는 b/t, CFRP쉬트 보강겹수이며, 총 6개의 실험체가 제작되었다. 실험변수로 사용된 판폭두께비는 b/t는 60, 80, 100이고 CFRP쉬트는 3겹 보강하였다. 실험결과 판폭두께비 100 실험체에서 CFRP쉬트 3겹 보강을 통해 내력을 16% 상승시켜 보강효과를 검증하였다. 내력 저하율을 검토한 결과 국부좌굴이 발생하지 않는 단면강도를 기준으로 최대 41%정도 내력이 저하되었으나, CFRP보강을 통해 32% 정도의 내력이 저하되어 보강효과를 검증할 수 있었다. 하중-변형를 관계를 보면 강재는 항복강도 이전에 국부좌굴이 발생하였으며, CFRP쉬트의 보강을 통해 국부좌굴을 지연시킴을 확인하였다.

• 대한조선학회논문집
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• 제34권3호
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• pp.53-60
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• 1997

일반적으로 선박 판부재의 좌굴강도에 대한 안전성 평가는 선체구조 설계단계에서 반드시 거쳐야 할 단계로 한 척의 배는 수많은 판부재로 구성되어 선박구조 전체에 대한 이론적이며 체계적인 시스템을 이용한 좌골강도평가의 정확도 및 효율성이 강조되고 있다. 그러나 현재의 판부재 좌굴강도를 평가하는 각 선급의 규정치가 많은 영향인자를 고려치 않고 있거나 함축척으로 고려하고 있기 때문에 경우에 따라서는 좌굴강도가 상당한 안전측의 값을 제시하는 등 실제 선급규정치의 사용에 제약을 주기도 한다. 따라서 본 연구에서는 면내인장력의 영향등 선급들의 좌굴 규정치뿐만이 아니라 면내인장력의 효과, 경계조건, 횡하중 및 잔류응력등을 고려하면서 손쉽게 좌굴평가를 수행할 수 있는 선진 좌굴평가시스템을 개발하였다. 이들 선진 좌굴평가시스템을 이용하면 선박판부재의 보다 정도 높고 효율적인 평가가 가능하리라 생각되며 앞으로 대중적인 사용을 위해 워크스테이션 외에도 개인용 컴퓨터에서의 시스템 구축을 계획하고 있다.

• 한국자동차공학회논문집
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• 제21권5호
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• pp.97-103
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• 2013

Crash performance of the straight member was studied by FE analysis. One end of model was fixed and the other end was impacted by 1,000kg rigid mass with velocity of 16.0m/sec. The maximum and mean load were discussed to compare crash performance. The members with various section shapes were analyzed and the flange location was changed. Also, spot weld points were added in the initial buckling region to investigate its effect. Final rectangular section model which has flanges at the center and reinforcement in initial buckling region showed high enhancement in crash performance.

• 한국공간구조학회:학술대회논문집
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• 한국공간구조학회 2008년도 춘계 학술발표회 논문집
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• pp.165-170
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• 2008

본 논문에서는 새로이 제안된 접합부를 가진 단층 래티스 돔의 비탄성 거동을 실험적으로 분석하였다. 구조적인 성능과 시공성을 모두 만족시키기 위해서 제안된 새로운 접합부를 적용하여 강관으로 구성된 스팬 7m의 축소 실험모델을 제작하였으며, 하중 전이장치를 이용하여 각 절점에 균일한 하중이 가력되는 정적 재하실험을 수행하였다. 최대 가력하중은 설계하중의 약 1.6배였으며, 일부 부재에서 압축 항복점을 넘어 비탄성 좌굴이 발생하였다. 좌굴 발생 이후에는 가력장치가 허용할 수 있는 변위까지 실험을 수행하였으며, 실험을 통해서 구해진 래티스 돔의 거동을 구조설계의 관점에서 분석하였다.

• 복합신소재구조학회 논문집
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• 제1권1호
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• pp.27-33
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• 2010

Static analyses and buckling analyses were carried out for buried GFRP pipes by using finite element method. Vehicle loads, vertical and lateral soil pressures were considered as external loads, and supplying water pressure was considered as an internal load. Nine types of the factory-manufactured GFRP pipes were analyzed. Their maximum stresses and displacements were compared with the limit displacements and ultimate stress. Additionally, stress analysis on an enhanced flange, which was designed to reduce stress concentration, was performed. A cantilever analysis was carried out to know the maximum stress on the neck of the flange, which is the critical part. And a static analysis was carried for the buried flange. The test results showed that GFRP pipes were safe and stable against the external loads. And they showed that the enhanced flange decreased about 35% of the stress concentration.

• International Journal of Aerospace System Engineering
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• 제6권1호
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• pp.1-7
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• 2019

In the present study, structural safety and stability on the main wing and tail planes of the 1.2 ton WIG(Wing in Ground Effect) flight vehicle, which will be a high speed maritime transportation system for the next generation, was performed. The carbon-epoxy composite material was used in design of wing structure. The skin-spar with skin-stressed structural type was adopted for improvement of lightness and structural stability. As a design procedure for this study, the design load was estimated with maximum flight load. From static strength analysis results using finite element method of the commercial codes. From the stress analysis results of the main wing, it was confirmed that the upper skin structure between the second rib and the third rib was unstable for the buckling load. Therefore in order to solve this problem, three stiffeners at the buckled region were added. After design modification, even though the weight of the wing was a little bit heavier than the target weight, the structural safety and stability was satisfied for design requirements.