• Steel and Composite Structures
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• 제1권1호
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• pp.75-96
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• 2001

Actual buckling curves are always characterised by the erosion of ideal buckling curves. In case of compact sections this erosion is due to the imperfections, while for thin-walled members, a supplementary erosion is induced by the phenomenon of coupled instabilities. The ECBL approach- Erosion of Critical Bifurcation Load - represents a practical and convenient tool to characterise the instability behaviour of thin-walled members. The present state-of-art paper describes the theoretical background of this method and the applications to cold-formed steel sections in compression and bending. Special attention is paid to the evaluation methods of erosion coefficient and to their validation. The ECBL approach can be also used to the plastic-elastic interactive buckling of thin-walled members, and the paper provides significant results on this line.

• Steel and Composite Structures
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• 제5권6호
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• pp.515-533
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• 2005

Buckling and post-buckling of cold-formed steel members are rather difficult to predict due to material and geometrical non-linearity. However, numerical techniques have reached a level of maturity such that many are now successfully undertaking ultimate strength analysis of cold-formed steel members. In numerical non-linear analysis, both geometrical and material imperfections, have to be estimated and properly used. They must be codified in terms of shape and magnitude. The presented paper represents a state-of-art report, including relevant results obtained by the authors and collected from literature, on that problem.

• Steel and Composite Structures
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• 제34권2호
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• pp.171-188
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• 2020

The past research on cold-formed steel (CFS) flexural members have proved that rectangular hollow flanged sections perform better than conventional I-sections due to their higher torsional rigidity over the later ones. However, CFS members are vulnerable to local buckling, substantially due to their thin-walled features. The use of packing, such as firmly connected timber planks, to the flanges of conventional CFS lipped I-sections can drastically improve their flexural performance as well as structural efficiency. Whilst several CFS composites have been developed so far, only limited packing materials have been tried. This paper presents a series of tests carried out on different rectangular hollow compression flanged sections with innovative packing materials. Four-point flexural tests were carried out to assess the flexural capacity, failure modes and deformed shapes of the CFS composite beam specimens. The geometric imperfections were measured and reported. The North American Specifications and Indian Standard for cold-formed steel structures were used to compare the design strengths of the experimental specimen. The test results indicate clearly that CFS rectangular 'compression' flanged composite beams perform significantly better than the conventional rectangular hollow flanged CFS sections.

• 한국강구조학회 논문집
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• 제10권4호통권37호
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• pp.677-689
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• 1998

본 연구에서는 중심압축력을 받는 스털스터드의 설계강도에 대하여 다루었으며 비교 평가하였다. 미국규준인 냉간성형 LRFD 설계규준 (AISI). 유럽의 냉간박벽부재설계규준 (EC3 part 1.3) 및 독일의 관련규정 (DASt-Richtlinie 016)의 유사성과 차이점을 소개하고 분석하며 체계적으로 평가하였다. 특히 유효폭과 전체 안정성문제 (휨좌굴과 비틀림좌굴)가 이 논문에서 내포되어 있다. 또한 예제를 통하여 두 규준인 AISI와 EC3에 의한 설계압축강도를 산정하고 비교 분석하였다.

• Steel and Composite Structures
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• 제4권5호
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• pp.367-384
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• 2004

A numerical model based on the finite element technique is adopted to investigate the behavior and strength of thin-walled I-section beam-columns. The model considers both the material and geometric nonlinearities. The model results were first verified against some of the currently available experimental results. A parametric study was then performed using the numerical model and interaction diagrams for the investigated beam-columns have been presented. The effects of the web depth-to-thickness ratio, flange outstand-to-thickness ratio and bending moment-to-normal force ratio on the ultimate strength of thin-walled I-section beam-columns were scrutinized. The interaction equations adopted for beam columns design by the NAS (North American Specifications for the design of cold formed steel structural members) have been critically reviewed. An equation for the buckling coefficient which considers the interaction between local buckling of the flange and the web of a thin-walled I-section beam-column has been proposed.

• 한국강구조학회 논문집
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• 제14권2호
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• pp.349-356
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• 2002

현재 우리나라 스틸하우스 건설에 사용하는 구조재는 SGC41 강종으로 제작된 보통 C-형강이나 Lip-C-형강이 주를 이루고 있으나 이 분야의 선진국가에서는 좌굴 강도가 높고 시공성이 좋은 고유의 단면 형상을 개발하여 사용하고 있다. 본 연구에서는 정량이면서 강도 및 강성이 높고 다양한 시공상 장점이 있는 고강도 신형상 박판냉간성형단면의 압축부재로서의 구조적인 고동과 성능을 연구하기 위하여 재료실험 및 압축실험을 수행하고 해석치와 비교하여 보았다.

• 한국강구조학회 논문집
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• 제15권3호
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• pp.281-290
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• 2003

신형상 폐단면 냉간성형형강 스터드와 래프터로 구성된 포탈프레임의 접합부의 모멘트-회전각 관계, 회전강성, 항복모멘트 및 극한모멘트 등을 파악하기 위하여 접합부실험을 수행하였다. 실험의 주요 변수는 연강 접합철물의 두께 및 형상과 접합부 시험체의 비틀림에 관한 구속조건이며, 실험결과의 검증을 위해서 비선형해석 결과와 비교하였다. 반강접 접합부의 휨강성을 실험에 의한 모멘트-회전각 곡선으로 부터 구한 할선강도로 제안하여 구조해석을 통하여 타당성을 검토하였다.

• Structural Engineering and Mechanics
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• 제46권3호
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• pp.323-335
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• 2013

This work aims to study the effect of stiffener ties in the behavior of intermediate length open section Cold-Formed Steel (CFS) Columns under axial compression. A comparative study on the behaviour and strength of Cold Formed Steel Columns by changing the direction of projection of lips (i.e., inwards or outwards) are also done. In this work two types of sections were considered Type-I section with lip projecting outwards (hat) and Type-II section with lip projecting inwards (channel). The length of the columns is predicted by performing elastic buckling analysis using CUFSM software. The theoretical analysis is performed using DSM - S100;2007, AS/NZ: 4600-2005 and IS: 801-1975. The compression tests are carried out in a 400 kN loading frame with hinged-hinged end condition. The non-linear numerical analysis is performed using Finite Element software ANSYS 12.0 to simulate the experimental results. Extensive parametric study is carried out by varying the width and spacing of the stiffener ties. The results are compared; the effects of stiffener ties on behaviour and load carrying capacity on both types of columns are discussed.

• Steel and Composite Structures
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• 제35권5호
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• pp.701-715
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• 2020

Steel storage racks are lightweight structures, made of thin-walled cold-formed members, whose behaviour is remarkably influenced by local, distortional and overall buckling phenomena, frequently mutually combined. In addition, the need of an easy and rapid erection and reconfiguration of the skeleton frame usually entails the presence of regular perforations along the length of the vertical elements (uprights). Holes and slots strongly influence their behaviour, whose prediction is however of paramount importance to guarantee an efficient design and a safe use of racks. This paper focuses on the behaviour of isolated uprights subjected to both axial load and bending moments, differing for the cross-section geometry and for the regular perforation systems. According to the European standards for routine design, four alternatives to evaluate the bending moment-axial load resisting domains are shortly discussed and critically compared in terms of member load carrying capacity.

• Steel and Composite Structures
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• 제42권4호
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• pp.447-458
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• 2022

Cold-formed steel (CFS) sections are thin-walled, therefore, more susceptible to different types of geometric imperfections. Global type of geometric imperfections has a significant impact on the load-carrying capacity of flexural members. This paper reports an experimental study that discusses the influence of global imperfections on the flexural response of CFS built-up I-beams composed of two lipped channels, with simply supported ends, under four-point loading. Global imperfections of magnitude over eight times the maximum permissible ones were induced in the specimens, leading to their distress. Using various simple stiffening schemes, the capacity and stiffness of the distressed specimens were improvised. The performance comparisons were made based on the maximum loads resisted, flexural stiffnesses offered, and failure modes experienced by the specimens. As experimental data on such distressed specimens are currently lacking in the literature, the test results of the present study will provide the necessary data needed by future researchers to numerically extend this study further, which will help in the development of necessary design guidelines for the same. The stiffening schemes significantly improved the structural efficiency of distressed specimens in terms of strength and stiffness, by over 60%. As a result, an effective and time-saving solution to such realistic structural engineering problems is given.