• Steel and Composite Structures
• /
• v.20 no.1
• /
• pp.57-70
• /
• 2016

The predominant type of buckling that I-steel concrete composite beams experience in the negative moment area is distortional buckling. The key factors that affect distortional buckling are the torsional and lateral restraints by the bottom flange. This study thoroughly investigates the equivalent lateral and torsional restraint stiffnesses of the bottom flange of an I-steel concrete composite beam under negative moments. The results show a coupling effect between the applied forces and the lateral and torsional restraint stiffnesses of the bottom flange. A formula is proposed to calculate the critical buckling stress of the I-steel concrete composite beams under negative moments by considering the lateral and torsional restraint stiffnesses of the bottom flange. The proposed method is shown to better predict the critical bending moment of the I-steel composite beams. This article introduces an improved method to calculate the elastic foundation beams, which takes into account the lateral and torsional restraint stiffnesses of the bottom flange and considers the coupling effect between them. The results show a close match in results from the calculation method proposed in this paper and the ANSYS finite element method, which validates the proposed calculation method. The proposed calculation method provides a theoretical basis for further research on distortional buckling and the ultimate resistance of I-steel concrete composite beams under a variable axial force.

• Steel and Composite Structures
• /
• v.14 no.6
• /
• pp.571-586
• /
• 2013

This paper focuses on the buckling capacity of a hybrid grid shell. The eigenvalue buckling, geometrical non-linear elastic buckling and elasto-plastic buckling analyses of the hybrid structure were carried out. Then the influences of the shape and scale of imperfections on the elasto-plastic buckling loads were discussed. Also, the effects of different structural parameters, such as the rise-to-span ratio, beam section, area and pre-stress of cables and boundary conditions, on the failure load were investigated. Based on the comparison between elastic and elasto-plastic buckling loads, the effect of material non-linearity on the stability of the hybrid barrel vault is found significant. Furthermore, the stability of a hybrid barrel vault is sensitive to the anti-symmetrical distribution of loads. It is also shown that the structures are highly imperfection sensitive which can greatly reduce their failure loads. The results also show that the support conditions pose significant effect on the elasto-plastic buckling load of a perfect hybrid structure.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.36 no.3
• /
• pp.193-201
• /
• 2023

In this study, a nonlinear truss finite element is developed to analyze structures with negative Poisson effect-induced tensile buckling. In general, the well-known buckling phenomenon is a stability problem under a compressive load, whereas tensile buckling occurs because of local compression caused by tension. It is not as well-known as classical buckling because it is a recent study. The mechanism of tensile buckling can be briefly explained from an energy standpoint. The nonlinear truss finite element with a torsional spring is formulated because the finite element has not been reported in the literature yet. The post-buckling analysis is then performed using the generalized displacement control method, which reveals that the torsional spring plays an important role in tensile buckling. Structures that mimic a negative Poisson effect can be constructed using such post-buckling behaviors, and one of the possible applications is a mechanical switch. The results obtained are compared to those of analytical solutions and commercial finite element analysis to assess the validity of the proposed finite element model. The numerical results show that the developed finite element model could be a viable option for the basic design of nonlinear structures with a negative Poisson effect.

• Structural Engineering and Mechanics
• /
• v.48 no.2
• /
• pp.275-289
• /
• 2013

The cross sections of multi-span beams are sometimes suddenly increased at the interior support of continuous beams to resist high negative moment. An earlier study on elastic lateral torsional buckling of stepped beams was conducted to propose new design equations. This research aims to continue the earlier study by considering the effect of inelastic buckling of stepped beams subjected to pure bending and general loading condition. A three-dimensional finite element-program ABAQUS and a statistical program MINITAB were used in the development of new design equations. The inelastic lateral torsional buckling strengths of 36 and 27 models for singly and doubly stepped beams, respectively, were investigated. The general loading condition consists of 15 loading cases based on the number of inflection point within the unbraced length of the stepped beams. The combined effects of residual stresses and geometrical imperfection were also considered to evaluate the inelastic buckling strengths. The proposed equations in this study will definitely improve current design methods for the inelastic lateral-torsional buckling of stepped beams and will increase efficiency in building and bridge design.

• Structural Engineering and Mechanics
• /
• v.5 no.1
• /
• pp.85-104
• /
• 1997

The paper investigates the influence of lateral restraint on the buckling behaviour of plate under non-uniform compression. The unloaded edges are assumed to be partially restrained against translation in the plane of the plate and the distributions of the resulting forces acting on the plate are shown. The stability analysis is done numerically using the Galerkin method and various strategies the economize the numerical implementation are presented. Results are obtained showing the variation of the buckling load, from free edge translation to fully restrained, with unloaded edges simply supported, clamped and partially restrained against rotation for various plate aspect ratios and stress gradient coefficients. An apparent decrease in the buckling load is observed due to these destabilizing forces acting in the plate and changes in the buckling modes are observed by increasing the intensity of the lateral restraint. A comparison is made between the budding loads predicted from various formulas in stability standards based on free edge translation and the values derived from the present investigation. A difference of about 34% in the predicted buckling load and different buckling mode were found.

• Computational Structural Engineering : An International Journal
• /
• v.3 no.1
• /
• pp.19-29
• /
• 2003

In the present study, finite element linear buckling analysis is performed for grid-stiffened composite plates. A hybrid element with drilling degrees of freedom is employed to reduce the effect of the sensitivity of mesh distortion and to match the degrees of freedom between skins and stiffeners. The preliminary static stress distribution is analyzed for the determination of accurate load distribution. Parametric study of grid structures is performed and three types of buckling modes are observed. The maximum limit of buckling load was found at the local skin-buckling mode. In order to maximize buckling loads, stiffened panels need to be designed to be buckled in skin-buckling mode.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.3 no.1
• /
• pp.146-154
• /
• 2000

Buckling behavior was studied for the square plate with bead and hole under shear load. Plates were made to examine the effect of bead and hole to the material, aluminum and composite, the effect of flange angle, bead height and bead radius of curvature. There was little difference between buckling loads obtained by the experiment and Rayleigh-Ritz method to the plate. Buckling load could be increased highly when stress concentration to the hole was dispersed effectively using flange. A well-designed plate using bead and flange showed 3 times as much as stiffness to the plate without bead and flange.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1993.10a
• /
• pp.63-67
• /
• 1993

In single-layer latticed domes with two-way grid, if we use the cross-membered junction's method for the advantage in fabrication and construction, the eccentricity is occurred in the nodal point of crossing members. This paper is aimed at investigating the buckling characteristics for the effect of eccentricity. Analysis method is based on FEM dealing with the geometically nonlinear deflection problems. As a result of the study, in the case of having eccentricity, the values of buckling strength are about 0.7 times than or not but the characteristics of buckling and deflection except buckling strength have a similar tendency each other.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.993-1000
• /
• 2006

Practical stability design method of main members of cable-stayed bridges is proposed and discussed through a design example. For this purpose, initial tensions of stay cables and axial forces of main members are firstly determined using initial shaping analysis of bridges under dead loads. And then the effective buckling length using system elastic/inelastic buckling analysis and bending moments considering $P-{\delta}-{\Delta}$ effect by second-order elastic analysis are calculated for main girder and pylon members subjected to both axial forces and moments, respectively. Particularly, load combinations of dead and live loads, in which maximum load effects due to live loads are obtained, are taken into account and effects of live loads on effective buckling lengths are investigated.

• Advances in nano research
• /
• v.4 no.4
• /
• pp.309-326
• /
• 2016

The buckling response of a single-layered graphene sheet (SLGS) embedded in visco-Pasternak's medium is presented. The nonlocal first-order shear deformation elasticity theory is used for this purpose. The visco-Pasternak's medium is considered by adding the damping effect to the usual foundation model which characterized by the linear Winkler's modulus and Pasternak's (shear) foundation modulus. The SLGS be subjected to distributive compressive in-plane edge forces per unit length. The governing equilibrium equations are obtained and solved for getting the critical buckling loads of simply-supported SLGSs. The effects of many parameters like nonlocal parameter, aspect ratio, Winkler-Pasternak's foundation, damping coefficient, and mode numbers on the buckling analysis of the SLGSs are investigated in detail. The present results are compared with the corresponding available in the literature. Additional results are tabulated and plotted for sensing the effect of all used parameters and to investigate the visco-Pasternak's parameters for future comparisons.