• 대한기계학회논문집
• /
• 제18권6호
• /
• pp.1496-1502
• /
• 1994

The influences of spring position and spring stiffness on the critical force of a cantilevered beam subjected to a follower force are investigated. The spring attatched to the beam is assumed to be a translational one and can be located at arbitrary positions of the beam as it has not been assumed so far. The effects of transeverse shear deformation and rotary intertia of the beam are also included in this analysis. The charateristic equation for the system is derived and a finite element model of the beam using local coordinates is formulated through extended Hamilton's principle. It is found that when the spring is located at position less than that of 0.5L, the flutter type instability only exists. It is shown that the spring position approaches to the free end of the beam from its midpoint, instability type is changed from flutter to divergence through the jump phenomina according to the increase of spring stiffness.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2003년도 춘계학술대회
• /
• pp.868-873
• /
• 2003

This paper deals with the linear dynamic response of an elastically restrained beam under a moving mass, where the elastic support was modelled by translational springs of variable stiffness. Governing equations of motion taking into account of all inertia effects of the moving mass were derived by Galerkin's mode summation method, and Runge-Kutta integration method was applied to solve the differential equations. The effects of the speed, the magnitude of the moving mass, stiffness and the position of the support springs on the response of the beam have been studied. A variety of numerical results allows us to draw important conclusions for structural design purposes.

• 한국정밀공학회지
• /
• 제13권2호
• /
• pp.176-184
• /
• 1996

The paper describes the vibration characteristics of the mechanical system consisting of a uniform Timoshenko beam with a guided mass and an elastic spring support. The free end of the beam does not rotate and the spring attatched to the guided mass is elastically restrained against translation. The guided mass is assumed to be a rigid body having a finite size, but not a mass point as it has been assumed so far. The effect of magnitudes, rotary inertia and the size of the guided mass on the vibration characteristics is fully investigated by the numerical simulation using FEM and experiment. In order to verify the eigenvalue sensitivity for considered system, comparison exact solutions with FEM is conducted, and a good agreement between two solutions is also highlighted.

• 소음진동
• /
• 제10권6호
• /
• pp.1022-1028
• /
• 2000

This paper presents a modeling method for the vibration analysis of rotating cantilever beams considering the elastic foundation effect. Mass and stiffness matrices are derided explicitly by considering coupling effect between stretching and bonding motion. Numerical results show that the bending direction elastic foundation stiffness influences the vibration characteristics significantly in practical range of beam configuration. The ranges of elastic foundation stiffness to avoid the dynamic buckling are also presented. The method presented in this paper can be used to predict the variations of natural frequencies of rotating cantilever beams with elastically restrained root.

• Advances in nano research
• /
• 제8권2호
• /
• pp.169-182
• /
• 2020

This study presents the hygro-thermo-electromagnetic mechanical vibration attributes of elastically restrained piezoelectric nanobeam considering effects of beam surface for various elastic non-ideal boundary conditions. The nonlocal Eringen theory besides the surface effects containing surface stress, surface elasticity and surface density are employed to incorporate size-dependent effects in the whole of the model and the corresponding governing equations are derived using Hamilton principle. The natural frequencies are derived with the help of differential transformation method (DTM) as a semi-analytical-numerical method. Some validations are presented between differential transform method results and peer-reviewed literature to show the accuracy and the convergence of this method. Finally, the effects of spring constants, changing nonlocal parameter, imposed electric potential, temperature rise, magnetic potential and moisture concentration are explored. These results can be beneficial to design nanostructures in diverse environments.

• Steel and Composite Structures
• /
• 제3권1호
• /
• pp.1-12
• /
• 2003

Cantilevers are unique statically determinate structural elements with respect to their mode of overall buckling, in that the tension flange is the critical flange under gravity loading, and is the flange that deflects greatest during overall buckling. While this phenomenon does not complicate the calculation of the lateral buckling load, either theoretically or in structural design codes, it has been shown in previous research that the influence of distortion in the elastic buckling of cantilevers is not the same as that experienced in the elastic buckling of simply supported beams. This paper extends the study of the distortional buckling of cantilevers into the hitherto unconsidered inelastic range of structural response. A finite element method for studying the inelastic bifurcative instability of members whose cross-sections may distort during buckling is described, and the efficacy of the method is demonstrated. It is then used to study the inelastic distortional buckling of hot-rolled I-section cantilevers with two common patterns of residual stresses, and which may be restrained elastically from buckling by other structural elements.

• 소음진동
• /
• 제4권4호
• /
• pp.469-478
• /
• 1994

This paper desfcribes the formulation for the analysis of the free vibration of a circular cylindrical shell with elastic supports by the transfer influence coefficient method. This method was developed on the base of the concept of the successive transmission of dynamic influence coefficients. The analysis algorithm for circular cylindrical shell elastically restrained by springs, which plays an important role in many industrial fields, is discussed. The supporting springs have the axial, circumferential, radial and rotational spring constants uniformly distributed along the circumference of the shell. The simple computational results on a personal computer demonstrate the validity of the present method, that is, the numerical high accuracy, the high speed analysis method and the flexibility for programming, compared with results of the transfer matrixmethod and reference. We also confirmed that the present algorithm could obtain the solutions of high accuracy for system with a number of intermediate rigid supports. And we could easily treat the intermediate support and all boundary conditions by adequately varying the values of spring constants.

• Steel and Composite Structures
• /
• 제19권6호
• /
• pp.1581-1598
• /
• 2015

A concentric 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 concentric 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. Weak-axis reinforcing members (2 pieces) developed from those suggested in previous studies (4 pieces) were used to reinforce the H-shaped braces in an inverted V-type braced frame. Monotonic loading tests, finite element analysis and cyclic loading tests were carried out to evaluate the structural performance of the reinforced braces and frames. The reinforced braces satisfied the AISC requirement. The reinforcement suggested in this study is expected to prevent the rupture of beams caused by the unbalanced resistance of the braces.

• Coupled systems mechanics
• /
• 제1권3호
• /
• pp.269-283
• /
• 2012

In the present paper, a multilevel approach for the local nanobuckling analysis of carbon nanotube (CNT) based composite materials is proposed and described. The approach comprises four levels, all of them at nanoscale. The first level aims to propose the potential that describes the interatomic forces between carbon atoms. In the second level, molecular dynamics simulations are performed to extract the elastic properties of the CNT. The third level aims to determine the stiffness of the material that surrounds the CNT (matrix), using the annular membrane analysis. In the fourth level, finite strip analysis of the CNT elastically restrained by the matrix is performed to calculate the critical strain at which the CNT buckles locally. In order to achieve accurate results and take the CNT-matrix interaction into account, the $3^{rd}$ and $4^{th}$ steps may be repeated iteratively until convergence is achieved. The proposed multilevel approach is applied to several CNTs embedded in a cylindrical representative volume element and illustrated in detail. It shows that (i) the interaction between the CNT and the matrix should be taken into account and (ii) the buckling at nanoscale is sensitive to several types of local buckling modes.

• 한국강구조학회 논문집
• /
• 제27권2호
• /
• pp.207-217
• /
• 2015

철골 중심 가새골조는 최소의 물량으로 건물의 횡력에 대한 저항력을 확보할 수 있는 매우 효과적인 시스템이다. 그러나 중심가새 골조는 탄성거동을 전제로 풍하중에 대한 구조시스템으로 비탄성거동을 수반하는 지진하중에 대해서는 가새 좌굴 이후의 에너지 소산능력저하와 반복하중 하에 가새 및 접합부의 취성파단 가능성이 제기된다. 그로 인해 가새의 좌굴이 최초로 발생한 층에 소성변형이 집중되어 연약층 발생에 의한 건물의 붕괴로 이어질 가능성이 높다. 따라서 본 논문에서는 기 설치된 H형 가새를 무용접 냉간성형보강재로 보강하여 휨-좌굴을 억제하고 인장력과 압축력에 동일한 강도를 확보하는 보강안에 대한 연구를 진행하였다.