• Computational Structural Engineering : An International Journal
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• 제3권1호
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• pp.49-59
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• 2003

This paper discusses the enhancement of the buckling capacity of column strips by use of piezoelectric layer. The analytical model for obtaining the buckling capacity of the piezoelectric coupled column with general boundary conditions modelled with different types of springs applied at the ends of the column is derived the first time. Based on this proposed model, the buckling capacity of the column strips can be accurately predicted by solving an eigenvalue problem. The computational results show the great potential of the piezoelectric materials in enhancing the buckling capacity of the column strips. The optimal locations of the piezoelectric layer for higher buckling capacity are also obtained for the columns with. standard pinned-pinned, fixed-free, and fixed-pinned structures. In addition, the buckling capacity and the increase of buckling capacity are discussed for those columns with the general boundaries as well. This research may provide a benchmark for the buckling analysis of the piezoelectric coupled strips.

• Steel and Composite Structures
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• 제9권2호
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• pp.89-101
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• 2009

This paper presents a simplified model to study post-buckling behaviours of the axially restrained steel column at elevated temperatures in fire. The contribution of axial deformation to the curvature of column section is included in theoretical equations. The possible unloading at the convex side of the column when buckling occurs is considered in the stress-strain relationship of steel at elevated temperatures. Parameters that affect structural behaviours of the axial restrained column in fire are studied. The axial restraint cause an increase in the axial force before the column buckles; the buckling temperature of restrained columns will be lower than non-restrained steel columns. However, the axial force of a restrained column decreases after the column buckles with the elevation of temperatures, so make use of the post-buckling behaviour can increase the critical temperature of restrained columns. Columns with temperature gradient across the section will produce lower axial force at elevated temperatures.

• Structural Engineering and Mechanics
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• 제26권6호
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• pp.651-672
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• 2007

This study presents an improved method that uses the elastic and inelastic system buckling analyses for determining the K-factors of steel column members. The inelastic system buckling analysis is based on the tangent modulus theory for a single column and the application is extended to the frame structural system. The tangent modulus of an inelastic column is first derived as a function of nominal compressive stress from the column strength curve given in the design codes. The tangential stiffness matrix of a beam-column element is then formulated by using the so-called stability function or Hermitian interpolation functions. Two inelastic system buckling analysis procedures are newly proposed by utilizing nonlinear eigenvalue analysis algorithms. Finally, a practical method for determining the K-factors of individual members in a steel frame structure is proposed based on the inelastic and/or elastic system buckling analyses. The K-factors according to the proposed procedure are calculated for numerical examples and compared with other results in available references.

• Computers and Concrete
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• 제18권5호
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• pp.1053-1063
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• 2016

As concrete is most usable material in construction industry it's been required to improve its quality. Nowadays, nanotechnology offers the possibility of great advances in construction. For the first time, the nonlinear buckling of straight concrete columns armed with single-walled carbon nanotubes (SWCNTs) resting on foundation is investigated in the present study. The column is modelled with Euler-Bernoulli beam theory. The characteristics of the equivalent composite being determined using the Mori-Tanaka model. The foundation around the column is simulated with spring and shear layer. Employing nonlinear strains-displacements, energy methods and Hamilton's principal, the governing equations are derived. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of SWCNTs, geometrical parameters, elastic foundation and boundary conditions on the buckling of column are investigated. Numerical results indicate that reinforcing the concrete column with SWCNTs, the structure becomes stiffer and the buckling load increases with respect to concrete column armed with steel.

• Computers and Concrete
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• 제17권5호
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• pp.567-578
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• 2016

As concrete is most usable material in construction industry it's been required to improve its quality. Nowadays, nanotechnology offers the possibility of great advances in construction. For the first time, the nonlinear buckling of straight concrete columns armed with single-walled carbon nanotubes (SWCNTs) resting on foundation is investigated in the present study. The column is modelled with Euler-Bernoulli and Timoshenko beam theories. The characteristics of the equivalent composite being determined using mixture rule. The foundation around the column is simulated with spring and shear layer. Employing nonlinear strains-displacements, energy methods and Hamilton's principal, the governing equations are derived. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of SWCNTs, geometrical parameters, elastic foundation and boundary conditions on the buckling of column are investigated. Numerical results indicate that reinforcing the concrete column with SWCNTs, the structure becomes stiffer and the buckling load increases with respect to concrete column armed with steel.

• 대한토목학회논문집
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• 제31권1A호
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• pp.1-7
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• 2011

이 연구는 일정표면적 기둥의 좌굴하중에 관한 연구이다. 기둥단면의 변화깊이의 형상함수로는 선형 변단면을 채택하였다. 이러한 기둥의 좌굴형상을 지배하는 상미분방정식을 유도하기 위하여 축방향 압축력을 받는 기둥의 동적 평형방정식을 이용하였다. 수치해석 예에서는 회전-회전, 회전-고정, 고정-고정의 지점조건을 고려하였다. 수치해석의 결과로 각종 기둥변수들이 좌굴하중에 미치는 영향을 분석하였다. 특히, 일정표면적으로부터 최대 좌굴하중을 발생시킬 수 있는 기둥의 최강단면비와 그에 대응하는 최강좌굴하중을 산정하였다. 기둥 축에 횡방향 내부지점을 설치하여 좌굴하중을 증가시킬 수 있는 무변위 위치를 찾기 위하여 기둥의 좌굴형상을 산출하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1988년도 가을 학술발표회 논문집
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• pp.36-42
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• 1988

In this study, a formulation of the idealized plate element based upon the idealized structural unit method(ISUM) firstly proposed by Ueda et．al is made in an attempt to analyze the geometric nonlinear behaviour up to the buckling strength of thin-walled long structures like box-column structure including the coupling effect between local and global buckling. An application to the example box-column is also performed and it is found that the present method gives reliable results with consuming very short computing times and therefore is very useful for evaluation of the buckling strength of thin-walled long structures.

• Wind and Structures
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• 제24권5호
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• pp.431-446
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• 2017

As concrete is most usable material in construction industry it's been required to improve its quality. Nowadays, nanotechnology offers the possibility of great advances in construction. In this study, buckling of horizontal concrete columns reinforced with Zinc Oxide (ZnO) nanoparticles is analyzed. Due to the presence of ZnO nanoparticles which have piezoelectric properties, the structure is subjected to electric field for intelligent control. The Column is located in foundation with vertical springs and shear modulus constants. Sinusoidal shear deformation beam theory (SSDBT) is applied to model the structure mathematically. Micro-electro-mechanic model is utilized for obtaining the equivalent properties of system. Using the nonlinear stress-strain relation, energy method and Hamilton's principal, the motion equations are derived. The buckling load of the column is calculated by Difference quadrature method (DQM). The aim of this study is presenting a mathematical model to obtain the buckling load of structure as well as investigating the effect of nanotechnology and electric filed on the buckling behavior of structure. The results indicate that the negative external voltage applied to the structure, increases the stiffness and the buckling load of column. In addition, reinforcing the structure by ZnO nanoparticles, the buckling load of column is increased.

• Wind and Structures
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• 제24권1호
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• pp.43-57
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• 2017

The use of nanotechnology materials and applications in the construction industry should be considered for enhancing material properties. However, the nonlinear buckling of an embedded straight concrete columns reinforced with silicon dioxide ($SiO_2$) nanoparticles is investigated in the present study. The column is simulated mathematically with Euler-Bernoulli and Timoshenko beam models. Agglomeration effects and the characteristics of the equivalent composite are determined using Mori-Tanaka approach. The foundation around the column is simulated with spring and shear layer. The governing equations are derived using energy method and Hamilton's principal. Differential quadrature method (DQM) is used in order to obtain the buckling load of structure. The influences of volume percent of $SiO_2$ nanoparticles, geometrical parameters and agglomeration on the buckling of column are investigated. Numerical results indicate that considering agglomeration effects leads to decrease in buckling load of structure.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.325-331
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• 2004

Generally, the buckling of thin-walled structures has studied for rectangular sections or circular sections. Rectangular sections have small stiffness and circular sections have large stiffness when they are compared with rectangular sections for local buckling. But both of them have similar stiffness to column buckling. Therefore in this paper, we are going to analyze the local buckling for the box section with rounded comer and compare with rectangular section. Also we confirm that the rounded comer section has larger local buckling strength than rectangular section.