• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.155-167
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• 2004

In this paper, the inelastic buckling behavior of the beam under uniform bending was investigated using the energy-based method, which can tackle problems in fourth order eigenvalue. The pattern of residual stress was not available to satisfy the I-sections manufactured in Korea. however; therefore, the well-known polynomial and simplified pattern of residual stress was adopted in this study. The inelastic lateral-distortional buckling behavior of the beam with I-sections manufactured in Korea was investigated. The study was then extended to the inelastic lateral-torsional buckling of the beam by minimizing the out-of-plane web distortion. The inelastic lateral-torsional buckling results obtained in this paper were compared with the prediction of allowable bending stress given in the Korean steel designers' manual (1995). Results showed that the importance of inelastic lateral-distortional buckling did not arise for beams under uniform bending. Likewise, the design method in KSDM (1995) was proven to bo too conservative for intermediate and short spans of beams without intermediate bracing.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.201-212
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• 1999

A beam supported by a flexible elastic support is commonly used as structural elements, e.g., braced beam, railway track, etc. The elastic support can be located in arbitrary point in the cross-section. This paper investigates the effects of support eccentricity on the elastic buckling of beams with elastic supports. The effects of stiffness of the elastic support are also studied. A beam element with elastic supports and the analysis program are developed for elastic buckling analysis using finite element formulation. The elastic support is modeled by elastic spring element. Using the offset technique, the eccentricity of support is taken into account. A beam element having 14 degrees of freedom including the warping degree of freedom is used. Various numerical example analyses show that the present formulation and analysis program accurately and effectively compute the buckling load and mode of beams with elastic supports.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.61-72
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• 2004

This study investigated the inelastic lateral-torsional buckling of simply supported beams under a central concentrated load and a uniformly distributed load. A line-type finite element, method was incorporated with the "so-called" simplified and polynomial patterns of residual stresses. The effect of the load height was also considered in this study. The polynomial residual stresses assumed in this study was a quartic distribution in the flange and a parabolic distribution in the web. The inelastic lateral-torsional buckling of beam was analyzed with four different I-sections manufactured in Korea. Results obtained in this study were compared with KSDM(design method in the 1995 Korean Steel Designers' Manual). The design method in KSDM was found to be generally conservative with and without a sub-beam attached to the main beam, which acted as an intermediate restraint.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.2
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• pp.11-15
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• 2009

This paper is concerned with the elastic buckling of thin-walled arches that are subjected to uniform bending. Nonlinear strain-displacement relations with the initial curvature are substituted into the second variation of the total potential energy to obtain the energy equation including initial curvature effects. The approximation for initial curvature effects that the bending normal strain distribution is linear across the cross section is applied consistently in the derivation process. The closed form solution is obtained for flexural-torsional buckling of arches under uniform bending and, it is compared with the previous theoretical results.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.175-181
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• 2008

Finite element buckling analyses of the monosymmetric I-beams subjected to t ransverse loading applied at different heights with respect to the mid-height of the cross section were conducted. Transverse loads consisting of a mid-span point load and a uniformly distributed load were considered in the investigation. The method suggested in the SRC Guide was compared with the finite element method (FEM) results. This paper presents a more accurate moment gradient correction factor for monosymetric I-beams considering the load height effect. The applicability of this new design method is limited to monosymmetric I-beams in which the degree of monosymetry, ${\rho}$, is from 0.1 to 0.9.

• Journal of Korean Society of Steel Construction
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• v.8 no.3 s.28
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• pp.79-87
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• 1996

본 논문에서는 단순지지된 일정체적의 정다각형 단면을 갖는 변단면 기둥의 정확탄성곡선(elastica)을 산출할 수 있는 수치해석법을 개발하였다. 정확탄성곡선의 미분방정식은 Bernoulli-Euler 보 이론으로 유도하였고, 미분방정식의 수치적분은 Runge-Kutta method를 이용하였다. 미분방정식의 고유치인 지점의 단면회전각은 Regula-Falsi method를 이용하여 계산하였다. 변단면의 단면 깊이의 변화식으로는 직선식, 포물선식 및 정현식의 3가지 함수식을 채택하였다. 또한 유도된 미분방정식을 이용하여 대상기둥의 좌굴하중을 산출하고 이로부터 최강기둥의 단면비와 좌굴하중을 결정하였다.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.207-217
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• 2015

A concentrically braced steel frame is a very efficient structural system because it requires relatively smaller amount of materials to resist lateral forces. However, primarily developed as a structural system to resist wind loads based on an assumption that the structure behaves elastically, a concentrically braced frame possibly experiences the deterioration in energy dissipation after brace buckling and the brittle failure of braces and connections when earthquake loads cause inelastic behavior. Consequently, plastic deformation is concentrated in the floor where brace buckling occurs first, which can lead to the rupture of the structure. This study suggests reinforcing H-shaped braces with non-welded cold-formed stiffeners to restrain flexure and buckling and resist tensile force and compressive force equally.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.53-60
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• 2008

The cross-sections of continuous multi-span beams sometimes suddenly increase, or become stepped, at the interior supports of continuous beams to resist high negative moments. The three-dimensional finite-element program ABAQUS (2007) was used to analytically investigate the inelastic lateral-torsional buckling behavior of stepped beams subjected to linear moment gradient and resulted in the development of design equations. The ratios of the flange thickness, flange width, and stepped length of beam are considered for the analytical parameters. Two groups of 27 cases and 36 cases, respectively, were analyzed for doubly and singly stepped beams in the inelastic buckling range. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. First, the distributions of residual stress of the cross-section is same as shown in Pi and Trahair (1995), and the initial geometric imperfection of the beam is set by central displacement equal to 0.1% of the unbraced length of beam. The new proposed equations definitely improve current design methods for the inelastic lateral-torsional buckling problem and increase efficiency in building and bridge design.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.13-24
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• 2017

System buckling analysis is usually used to determine the critical buckling load in the buckling design of cable-stayed bridges. However, system buckling analysis may yield unexpectedly large effective lengths of the members subjected to a relatively small axial force. This paper proposes a new method to determine reasonable effective lengths of girder and tower members in steel cable-stayed bridges using fictitious axial forces. An improved inelastic buckling analysis with modified tangent modulus is also presented. The effective lengths of members in example bridges calculated using the proposed method are compared with those obtained using the conventional buckling analysis method. The proposed method provides much more resonable effective lengths of the members. When girder and tower members are built with HSB800 steel instead of conventional steel, the effective lengths of the members under a small axial force slightly decreases in the inelastic buckling analysis without fictitious axial forces, while the proposed method that considers fictitious axial forces provides almost no changes in such lengths.

• Computational Structural Engineering
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• v.7 no.4
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• pp.151-158
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• 1994

The free vibrations of thermally buckled, simply supported, symmetrically laminated, rectangular, and quasi-isotropic plates are investigated. The nonlinear postbuckling analysis is performed by the finite element method based on the first order shear deformable plate theory with the use of von Karman type nonlinear strains and the Duhamel-Newman type constitutive law. The postbuckling solutions are used to obtain free vibration responses of buckled plates. Several numerical examples for quasi-isotropic laminated plates are considered. The effects of width-to-thickness ratios and aspect ratios on the free vibration characteristics of buckled plates are investigated.