• Steel and Composite Structures
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• 제30권5호
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• pp.471-481
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• 2019

Beam-columns are structural members subjected to a combination of axial and bending forces. Lateral-torsional buckling is one of the main failure modes. Beam-columns that are bent about its strong axis may buckle out of the plane by deflecting laterally and twisting as the values of the applied loads reach a limiting state. Lateral-torsional buckling failure occurs suddenly in beam-column elements with a much greater in-plane bending stiffness than torsional or lateral bending stiffness. This study intends to establish a unique convenient closed-form equation that it can be used for calculating critical elastic lateral-torsional buckling load of beam-column in the presence of a known axial load. The presented equation includes first order bending distribution, the position of the loads acting transversely on the beam-column and mono-symmetry property of the section. Effects of axial loads, slenderness and load positions on lateral torsional buckling behavior of beam-columns are investigated. The proposed solutions are compared to finite element simulations where thin-walled shell elements including warping are used. Good agreement between the analytical and the numerical solutions is demonstrated. It is found out that the lateral-torsional buckling load of beam-columns with mono-symmetric sections can be determined by the presented equation and can be safely used in design procedures.

• Composites Research
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• 제28권5호
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• pp.297-310
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• 2015

This study aims to develop efficient composite laminates for buckling load enhancement, interlaminar shear stress minimization, and weight reduction. This goal is achieved through cover-skin lay-ups around skins and stiffeners, which amplify bending stiffness and defer delamination by means of effective stress distribution. The design problem is formulated as multi-objective optimization that maximizes buckling load capability while minimizing both maximum out-of-plane shear stress and panel weight. For efficient optimization, response surface methodology is employed for buckling load, two out-of-plane shear stresses, and panel weight with respect to one ply thickness, six fiber orientations of a skin, and four stiffener heights. Numerical results show that skin-covered composite stiffened panels can be devised for maximum buckling load and minimum interlaminar shear stresses under compressive load. In addition, the effects of different material properties are investigated and compared. The obtained results reveal that the composite stiffened panel with Kevlar material is the most effective design.

• Structural Engineering and Mechanics
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• 제60권5호
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• pp.781-794
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• 2016

Due to its relatively good safety performance and aesthetic benefits, laminated glass (LG) is increasingly being used as load-carrying members in modern buildings. This paper presents an experimental study into one applicational scenario of structural LG subjected to in-plane bending. The aim of the study is to reveal the in-plane behaviors of the LG beams made up of multi-layered glass sheets. The LG specimens respectively consisted of two, three and four plies of glass, bonded together by two prominent adhesives. A total of 26 tests were carried out. From these tests, the structural behaviors in terms of flexural stiffness, load resistance and post-breakage strength were studied in detail, whilst considering the influence of interlayer type, cross-sectional interlayer percentage and presence of shear forces. Based on the test results, analytical suggestions were made, failure modes were identified, corresponding failure mechanisms were discussed, and a rational engineering model was proposed to predict the post-breakage strength of the LG beams. The results obtained are expected to provide useful information for academic and engineering professionals in the analysis and design of LG beams bending in-plane.

• 대한조선학회논문집
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• 제57권6호
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• pp.353-364
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• 2020

This paper presents the semi-analytical ice load calculation methods that are useful to simulate the ice-breaking process. Since the semi-analytical methods rely on the previously developed closed form equations or numerical analysis results, the user's exact understanding for the equations must be supported in order to use the methods properly. In this study, various failure modes of ice such as local crushing, in-plane splitting failure, out-of-plane bending failure and radial or circumferential cracking with rotation of the broken ice floe are considered. Based on the presented methods, the fracture modes were evaluated according to the size and thickness of ice. In addition, time series analysis for the ice-breaking process was performed on several ice conditions and the results were analyzed.

• Structural Engineering and Mechanics
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• 제15권5호
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• pp.495-511
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• 2003

New material applications and transparency are desired by contemporary architects. Its superb transparency and high strength make glass a very suitable building material -in spite of its brittleness- even for primary load bearing structures. Currently we will focus on load bearing glass beams, subjected to different loading types. Since glass beams have a very slender, rectangular cross section, they are sensitive to lateral torsional buckling. Glass beams fail under a critical buckling load at stresses that lie far below the theoretical simple bending strength, due to the complex combination of torsion and out-of-plane bending, which characterises the instability phenomenon. The critical load can be increased considerably by preventing the upper rim from moving out of the beam's plane. Different boundary conditions are examined for different loading types. The load carrying capacity of glass beams can be increased three times and more using relatively simple, cheap lateral restraints.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.165-169
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• 2000

A simple method was suggested to calculate the stress intensity factor for a one-sided patched crack with finite thickness. To consider out-of-plane bending effect resulting from the load-path eccentricity, the spring constant as a function of the through-thickness coordinate z was calculated from the stress distribution in the un-cracked plate, ${\sigma}_{yy}(y=0,\;z)$, and the displacement for the representative single strip Joint, $u_y(y=0,\;z)$. The stress Intensity factors were obtained using Rose's asymptotic solution approach and compared with the finite element results. In short crack region, two results had a little difference. However, two results were almost same in long crack region. On the other hand, the stress intensity factor using plane stress assumption was more similar to finite element result than plane strain condition.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.65-68
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• 2008

구조실험에서 실험장치의 구성방법은 실험 결과에 결정적인 영향을 미치는 중요한 요소이다. 가력 장치와 치구를 어떻게 구성하느냐에 따라서 의도하는 실험조건이 구현될 수 있다. 특히, 실물구조물과 같은 대형 실험체를 이용하여 실험하는 경우에는 실험장치를 구성하는 경제적 비용을 감안하여 정확한 하중을 가력하기 위한 실험장치의 구성이 더욱 중요하다. 본 논문은 이와 같은 필요성에 의하여 구조실험시설에서 일반적으로 이용하고 있는 설비를 이용하여 경제적이고 효과적인 실험장치를 구성하여 대형 보형실험체의 실험을 수행하고 그 결과를 기술하기 위하여 작성되었다.

• 대한기계학회논문집
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• 제16권5호
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• pp.864-872
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• 1992

본 연구에서는 이중노출 홀로그래피 간섭계의 원리를 이용하여 임의의 2차원 적 변형에 있어서 면외 변위와 면변위(in-plane displacement) 각각에 대한 홀로그램 을 제작하고 이를 컴퓨터에 입력하여 간섭무늬를 해석함으로써 변위와 변형률의 정량 화를 시도하였다.

• Structural Engineering and Mechanics
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• 제49권2호
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• pp.273-283
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• 2014

According to deformation features of pre-twisted bar, its elastic bending and torsion buckling equation is developed in the paper. The equation indicates that the bending buckling deformations in two main bending directions are coupled with each other, bending and twist buckling deformations are coupled with each other as well. However, for pre-twisted bar with dual-axis symmetry cross-section, bending buckling deformations are independent to the twist buckling deformation. The research indicates that the elastic torsion buckling load is not related to the pre-twisted angle, and equals to the torsion buckling load of the straight bar. Finite element analysis to pre-twisted bar with different pre-twisted angle is performed, the prediction shows that the assumption of a plane elastic bending buckling deformation curve proposed in previous literature (Shadnam and Abbasnia 2002) may not be accurate, and the curve deviates more from a plane with increasing of the pre-twisting angle. Finally, the parameters analysis is carried out to obtain the relationships between elastic bending buckling critical capacity, the effect of different pre-twisted angles and bending rigidity ratios are studied. The numerical results show that the existence of the pre-twisted angle leads to "resistance" effect of the stronger axis on buckling deformation, and enhances the elastic bending buckling critical capacity. It is noted that the "resistance" is getting stronger and the elastic buckling capacity is higher as the cross section bending rigidity ratio increases.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.281-286
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• 2008

Wall thinning defect due to flow accelerated corrosion is one of major aging phenomena in most power plant industries, and it results in reducing load carrying capacity of the piping systems. A failure testing system was set up for real scale elbows containing various simulated wall thinning defects, and monotonic in-plane bending tests were performed under internal pressure to find out the failure behavior of thinned elbows. Various finite element models were generated and analysed to figure out and simulate the behavior for other thinning shapes and loading conditions. This paper presents the decreasing trends of load carrying capacity according to the thinning dimensions which were revealed from the investigation of finite element analysis results. A mechanical integrity evaluation model for thinned elbows was proposed, also. This model can be used to calculate the TES plastic load of thinned elbows for general internal pressure, thinning location, and in-plane bending direction.