• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.4A
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• pp.465-474
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• 2008

Generally design of frame structures composed of beam-column member is accomplished by stability evaluation of each member considering the effective buckling length. This study selects a member of the smallest non-dimension slenderness ratio using the buckling eigenvalue calculated by the elastic buckling eigen-value analysis and axial force of the each member, and decides the initial deflection quantity reflected geometric and material nonlinearities from a suggested equation on the base of standard strength curve of Korea Bridge Design Code. Second-order elastic analysis applying the initial deflection is executed and the stability of each member is evaluated and decides ultimate strength. Through examples of eight-stories and four-stories plane frame structures, the evaluation of the stability is compared with the existing method and ultimate strength of the suggested method is compared with ultimate strength by the nonlinear inelastic analysis. Through these procedures, the increasing of effective buckling length by elastic buckling eigenvalue analysis is prevented from a new design method that considers initial imperfections. And the validity of this method is proved.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.101-104
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• 2008

일반적으로 연속경간을 가지는 강합성 I-형강 교량에 있어서 내부 지점 부근에서 상대적으로 큰 부모멘트가 발생하므로, 이에 경제적인 단면 활용을 위하여 변단면을 적용하여 휨강도를 증가시킨다. 본 연구에서는 기존 강도계산식에 관한 연구를 토대로 하여 비탄성 구간에 있는 변단면 I형보의 횡-비틀림 좌굴강도를 유한요소해석프로그램 ABAQUS(2007)를 이용하여 산정하고, 간편한 설계식을 제안하고 있다. 지간 한쪽 끝에 계단식 단면변화를 가지는 보에 대해서 고려하였으며, 플랜지 길이방향 비, 너비방향 비, 두께의 비로 계단식 I형보를 나타내었다. 해석에 사용된 단면매개변수는 36가지 조합이며, 비탄성 횡-비틀림 거동을 고려하기위하여 잔류응력 및 초기결함을 고려한 비선형해석을 실시하였는데, Pi(1995)등이 고려한 잔류응력의 형상과 국내 I형강 표준 치수 허용치에 근거하여 부재 길이의 0.1%를 초기제작오차로 고려하였다. 해석모델의 양쪽 끝단에는 모멘트하중을 재하하였다. 개발 제한된 식은 선형 모멘트 하중이 작용할 때 적용가능한 식으로 경제적이고 합리적인 설계에 적극 활용될 수 있을 것이다.

• Journal of the Society of Naval Architects of Korea
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• v.38 no.1
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• pp.72-85
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• 2001

A study for the structural strength evaluation on the doubler plate subjected to the biaxial in-plane compression has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. A1so, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et a1. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.4
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• pp.92-105
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• 2000

A study for the structural strength evaluation on the slender doubler plate has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate subjected to the longitudinal in-plane compression, elasto-plastic large deflection analysis is introduced including the contact effect between main plate and doubler. The characteristics of stiffness and strength variation are discussed based on their results. Also, in order to compare the doubler structure with the original strength of main plate without doubler, a simple formula for the evaluation of the equivalent flat plate thickness is derived based on the additional series analysis of flat plate structure. Using this derived equation, the thickness change of a equivalent flat plate is analyzed according to the variation of various design parameters of doubler plate and some design guides are suggested in order to maintain the original strength of main plate without doubler reinforcement. Finally, correlation between derived equivalent flat plate formula and the developed buckling strength formulas by author et al. is discovered and these relations are formulated for the future development of simple strength evaluation formula of doubler plate structure.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.99-106
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• 2006

Due to single symmetry of cross section, T-shaped members are likely to buckle in a flexural-torsional mode when they are subjected to axial compression. Therefore, the flexural-torsional buckling can be regarded as a governing mode of global buckling. An experimental program has been carried out to investigate the flexural-torsional buckling behavior of pultruded T-shaped members. Two types of pultruded members were tested in the experiment, and they were made of either E-glass/vinylester or E-glass/polyester. Lay-up and thickness of reinforcing layers, volume fractions of each constituents in layers, mechanical properties were experimentally determined. Two sets of knife edge fixure were used to simulate simple support condition for flexure and twisting, and the lateral displacements and the angle of twist were measured using three potentiometers. Every specimen buckled in a flexural-torsional mode, and most of the specimens showed post-buckling strength.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.231-241
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• 2015

The direct strength method (DSM) has been adopted by the NAS (2004) and AS/NZS 4600 (2005) for the design of cold-formed steel members. The method can be successfully applied to the design of welded steel members. This paper reviews the development of the DSM for welded steel structural members. The design strength formulae for welded section columns and beams for the DSM are based on the test results performed on welded H-section, C-section, circular and rectangular hollow section columns, plate girders and stiffened plates. The comparison between the design strength of welded sections predicted by the DSM and that estimated by existing specifications is also provided. The comparison verifies that the DSM can properly predict the compressive, flexural and shear strength of welded section columns and beams with the interaction between local and overall buckling.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.451-458
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• 2012

The concrete-filled steel tube (CFT) that has an excellent performance can be more economically used when the steel tube has a large width-to-thickness ratio. However, the international provisions such as American Institute of Steel Construction (AISC) limit the use of a slender plate in CFT members, resulting in a less optimal use of CFT. This study verifies the post buckling strength of CFT columns through the experimental program for Hollow Steel Sections (HSS) and CFTs with a with-to-thickness ratio ranged 60 to 100. The study also proposes a relaxed limitations of with-to-thickness ratio compared to the one specified in the current standards.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.10-19
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• 2014

Corrugated steel plates are made by fabricating thin steel plates to have trapezoidal or sinusoidal corrugation, and the corrugated plates are able to maintain high out-of-plane rigidity even when they are used instead of thick flat plates. Also, corrugated steel plates have almost no axial rigidity due to the accordion effect. Thus, if they are applied to the webs of plate girders, designing can be easily conducted so that the webs bear only shear stresses. However, unlike flat plates, the shear buckling of corrugated steel plates has very complex characteristics where buckling occurs due to the interaction of local and global buckling, besides local buckling and global buckling. For the investigation of the cause and characteristics of this interactive buckling, studies on sinusoidal corrugated steel plates are fewer than studies on trapezoidal corrugated steel plates. Therefore, in this study, the shear buckling characteristics of sinusoidal corrugated steel plates and the occurrence pattern of interactive buckling were investigated. For the calculation of shear buckling strength, a finite element program was used, and the analysis results were compared with the exact solution. In addition, the characteristics of buckling stress change and the change of buckling mode shape depending on corrugation thickness and shape parameter were analyzed, and by comparing these results with the results of a theoretical equation, the timing of buckling mode change was analyzed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.6A
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• pp.347-354
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• 2012

In this study, the equations of torsional and warping constants of a I-shaped plate girder with sine corrugated web are suggested. Because of geometric characteristics of the section, a I-shaped plate girder with corrugated web shows high out-of-plane stiffness, shear strength, and torsional stiffness. Torsional constant and warping constant definitely affect lateral-torsional buckling loads. Therefore, exact estimation of the sectional properties is quite important. But, it is difficult to estimate these properties by former methods. So, this study was focused on suggestion of the rational equations to calculate torsional and warping constants. In order to investigate the effects of geometric characteristics of sine-corrugated webs on torsional stiffness and warping torsional constant, finite element analyses for pure torsional behavior and warping torsional behavior of I-shaped plate girders were performed. By regression analyses of the analytical results, rational equations of the torsional constant and warping constant were suggested. Suggested equations for the properties were validated based on the analytical results of lateral-torsional buckling of simply supported I-shaped plate girder. By suggested equations, torsional and warping constants of I-shaped plate girders with a sine-corrugated web can be rationally estimated and more exact lateral-torsional buckling load can be simply calculated.

• Journal of Korean Society of Steel Construction
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• v.15 no.4 s.65
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• pp.423-433
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• 2003

Many study have been performed to describe the elastic and inelastic behavior of H-shaped beams with web openings that generally concentrated on the monotonic loading condition and concentric web opening. The findings of the studies led Darwin to propose formulas for the design of beams with web openings considering local buckling. While the formulas are simple and useful in real situation, more studies arc needed on their cyclic loading condition. In this experimental study, 12 H-shaped beams with web openings under cyclic loading condition were investigated. The dimension criteria based on the formulas proposed by Darwin were examined. The suitability of existing design formulas and the effects of plastic hinges on beams with web openings and of local buckling around web openings on the beam strength under cyclic loading were also studied. This was done by observing their behavior with various dimensional openings, eccentric per cent, and stiffeners.