The Experts below are selected from a list of 282 Experts worldwide ranked by ideXlab platform

Eduardo Bayo - One of the best experts on this subject based on the ideXlab platform.

  • A Direct Method for Buckling Analysis of Single Layer Lattice Structures
    International Journal of Space Structures, 2002
    Co-Authors: A Loureiro, Rufino Goñi, Eduardo Bayo
    Abstract:

    Numerous authors have studied the buckling behaviour of single layer lattice structures. Issues such as the buckling analysis in the elastic and plastic ranges, and the effects of imperfections in the failure mechanism of the structure have been investigated. However, there is still an uncertainty at the time of performing the buckling design of individual elements within the structure. This uncertainty stems from the need to approximate the Effective Length of each individual member. In addition, the approximate design criteria established by the different codes, and in particular Eurocode 3, are generally applicable to planar frames, but uncertain for spatial structures. This paper presents a direct one-step method for the buckling analysis of single layer lattice structures. The method avoids the use of the Effective Length Factor of each individual element. The key point is to perform a non-linear analysis of the structure starting from an initial deformation state that includes the initial imperfecti...

  • An efficient and direct method for buckling analysis of steel frame structures
    Journal of Constructional Steel Research, 2001
    Co-Authors: Eduardo Bayo, A Loureiro
    Abstract:

    Abstract The buckling analysis of steel frame structures is customarily carried out in a two step approach. Firstly, an analysis of the structure, generally linear–elastic, is performed to obtain the internal forces and moments; and secondly, the buckling analysis and design is done for each individual element taking into account an initial imperfection. Steel design codes, and in particular Eurocode-3 (EC3), base the buckling analysis upon the element Effective Length Factor K. This Factor depends on the buckling shape of that particular element within the structure, and in practical cases it is obtained by means of approximations or even by mere estimation. This paper presents a direct one-step method for the buckling analysis of steel frame structures. The method avoids the use of the Effective Length Factor of each individual element. The key point is to perform a non-linear analysis of the structure starting from an initial deformation state that includes the initial imperfections of the elements. Such initial deformation state is obtained from the first buckling mode of the structure by a suitable scaling procedure based on an energy approach. The resulting initial deformed shape is introduced along with the external loads in a fully non-linear structural analysis that yields the resulting element stresses including the buckling effects. The performance of the method is checked against the procedures established in EC3 by means of a series of numerical examples.

Dong-ho Choi - One of the best experts on this subject based on the ideXlab platform.

  • System buckling analysis for multi-story frames subjected to nonconservative forces
    International Journal of Steel Structures, 2015
    Co-Authors: Dong-ho Choi
    Abstract:

    The evaluation of the Effective Length Factor ( K -Factor) of columns based on the system buckling approach is a convenient tool in the stability design of multi-story frames. This method is superior to other analytical approaches, such as isolated subassembly and story-based approaches, in that inter-column and inter-story interactions are inherently taken into account. In this study, in order to investigate the effect of nonconservative forces on buckling loads and K -Factors for the single- and multistory framed structures, the system buckling approach is presented. For this purpose, the finite element model, based on the Hamilton’s principle, is formulated for the stability analysis of framed structures subjected to nonconservative forces. In numerical examples, buckling loads and K -Factors for single- and multi-story frames subjected to conservative or nonconservative forces are evaluated and compared with those obtained by other researchers. Especially the effect of the stiffness ratio of girder to column on K -Factors is investigated for nonconservative systems.

  • Iterative system buckling analysis, considering a fictitious axial force to determine Effective Length Factors for multi-story frames
    Engineering Structures, 2009
    Co-Authors: Dong-ho Choi, Hoon Yoo
    Abstract:

    Traditional elastic buckling analysis, based on the system buckling approach, is a convenient tool for the evaluation of Effective Length Factors of columns, in the stability design of multi-story frames. This method is superior to other analytical approaches, such as the isolated subassembly and story-based approaches, in that the inter-story and inter-column interactions are inherently taken into account. Nevertheless, use of the conventional critical load expression, in combination with results of elastic buckling analysis, may yield an excessively large Effective Length in members having relatively small axial forces. The present paper proposes an iterative elastic buckling analysis to determine reasonable Effective Length Factors of columns in multi-story frames. In this paper, numerical procedures for an iterative buckling analysis using a modified geometric stiffness matrix, are described to obtain the Effective Length Factors of the columns in multi-story frames. The axial force term in the geometric stiffness matrix is modified by adding a fictitious axial force to make the columns buckle along with the overall buckling of the frame. Iterative eigenvalue analysis is performed using the modified geometric stiffness matrix, to obtain the Effective Length Factors of each column using the critical load expression. Example frames presented in this paper demonstrate that the proposed method not only provides excellent outcomes by amending the weakness associated with traditional elastic buckling analysis for determining the Effective Length Factor, but is also a competitive alternative in the design of multi-story frames.

Wang Yan - One of the best experts on this subject based on the ideXlab platform.

  • ELASTIC STABILITY ANALYSIS OF COLUMN IN STEEL FRAMES WITH REDUCED BEAM SECTION CONNECTIONS
    Engineering mechanics, 2012
    Co-Authors: Wang Yan
    Abstract:

    By using rotational displacement equation of beams with varied cross-section and analyzing the effect of the column proximal end,the paper derives the equations for determining the Effective Length Factor of columns in non-sway and sway steel frames with RBS(reduced beam section) connections.To do that,modified linear stiffness ratio is introduced,which can be written as a formula similar to that in appendix D in ‘Code for Design of Steel Structure’.The results show that Effective Length Factor of non-sway RBS steel frames is very close to that of non-sway conventional steel frames,so the paper suggests that the Effective Length Factor of columns in non-sway RBS frames can be replaced by that of columns in non-sway conventional steel frames;but the Effective Length Factor of sway RBS steel frames is greatly large compared with that of sway conventional steel frames,which should be considered in engineering design.

  • Effective Length Factor of columns in semi rigid jointed and braced frames with consideration of shear effects
    Engineering mechanics, 2008
    Co-Authors: Wang Yan
    Abstract:

    In order rationally to evaluate the stability of columns in semi-rigid jointed and braced frames, the equations for determining the Effective Length Factor of columns are derived by considering the effects of the non-linear moment-rotation characteristics of beam-to-column connections and shear deformation. In this study, to derive the equations, a rotation spring with variable stiffness is used to model the flexibility of a beam-column connection and the modified stiffness Factor of a semi-rigid connection is introduced. It is shown that the Effective Length Factor of braced semi-rigid steel frames is notably different due to shear-deformation effects in the stability analysis for columns with less slenderness ratios. As a result of the weak restrictions by the semi-rigid connections to the column, there will be some errors in buckling calculations if not considering the effects of shear deformation. And also, the Effective Length Factor (μ-Factor) will have an increase of 5.6%―10%. Therefore, the effects of shear deformation should be considered in stability analysis of braced semi-rigid steel frames.

A Loureiro - One of the best experts on this subject based on the ideXlab platform.

  • A Direct Method for Buckling Analysis of Single Layer Lattice Structures
    International Journal of Space Structures, 2002
    Co-Authors: A Loureiro, Rufino Goñi, Eduardo Bayo
    Abstract:

    Numerous authors have studied the buckling behaviour of single layer lattice structures. Issues such as the buckling analysis in the elastic and plastic ranges, and the effects of imperfections in the failure mechanism of the structure have been investigated. However, there is still an uncertainty at the time of performing the buckling design of individual elements within the structure. This uncertainty stems from the need to approximate the Effective Length of each individual member. In addition, the approximate design criteria established by the different codes, and in particular Eurocode 3, are generally applicable to planar frames, but uncertain for spatial structures. This paper presents a direct one-step method for the buckling analysis of single layer lattice structures. The method avoids the use of the Effective Length Factor of each individual element. The key point is to perform a non-linear analysis of the structure starting from an initial deformation state that includes the initial imperfecti...

  • An efficient and direct method for buckling analysis of steel frame structures
    Journal of Constructional Steel Research, 2001
    Co-Authors: Eduardo Bayo, A Loureiro
    Abstract:

    Abstract The buckling analysis of steel frame structures is customarily carried out in a two step approach. Firstly, an analysis of the structure, generally linear–elastic, is performed to obtain the internal forces and moments; and secondly, the buckling analysis and design is done for each individual element taking into account an initial imperfection. Steel design codes, and in particular Eurocode-3 (EC3), base the buckling analysis upon the element Effective Length Factor K. This Factor depends on the buckling shape of that particular element within the structure, and in practical cases it is obtained by means of approximations or even by mere estimation. This paper presents a direct one-step method for the buckling analysis of steel frame structures. The method avoids the use of the Effective Length Factor of each individual element. The key point is to perform a non-linear analysis of the structure starting from an initial deformation state that includes the initial imperfections of the elements. Such initial deformation state is obtained from the first buckling mode of the structure by a suitable scaling procedure based on an energy approach. The resulting initial deformed shape is introduced along with the external loads in a fully non-linear structural analysis that yields the resulting element stresses including the buckling effects. The performance of the method is checked against the procedures established in EC3 by means of a series of numerical examples.

Hai Ying Wan - One of the best experts on this subject based on the ideXlab platform.

  • Column Effective Length Factor and Girder Parametric Analysis for the Components of Xinqiao International Airport Terminal
    Advanced Materials Research, 2011
    Co-Authors: De Zhang Li, Da Yi Ding, Yuan Qing Wang, Li Yuan Liu, Hai Ying Wan
    Abstract:

    The steel structure of Hefei Xinqiao International Airport Terminal was taken as a background of this article. The large-span frame is a typical frame of the structure. The curved box-girders are the critical parts of the whole frame. This paper focused on the mechanical properties of the curved girders, as well as the influence on box-columns connected with them. Stability problem is a key problem in the steel structure design, and Effective Length Factor is a way to reflect the stability problem in code for design. In this paper, the whole model of the airport terminal was established to conduct eigenvalue buckling analysis to obtain Effective Length Factors of the box-columns connected to the curved box-girder. In the finite model, a unified axial force was applied on the end of the box-column, and the elements of the box-columns and the adjacent members were refined. Then the Effective Length Factors were derived through the buckling models. In this paper, the curved box-girders of Hefei airport building were studied using finite element software ANSYS. The local model of the curved box-girders were set up to study the mechanical properties of the curved girders including the ultimate capacity analysis. Parametric analysis of the girders was carried out, and the results could be used to guide the design. The results show that finite element method is a convenient way of calculating Effective Length Factors for members with complex boundary conditions, and analysis of local models provides reasonable suggestions for design.