International Journal of Structural Stability and Dynamics

In this paper, the vibration and damping of a hollow sandwich box column containing a viscoelastic layer (VEL) or an electrorheological (ER) or magnetorheological (MR) fluid core with a constraining layer are analyzed and a comparison of performance is made. The hollow sandwich box column comprises two skin plates and a VEL/ER/MR fluid core layer. The finite element method is used to study the vibration and damping behaviors of the column. The natural frequencies and modal loss factors are obtained by solving the complex eigenvalue problem. The modal dampings and natural frequencies of the column are calculated for various electric as well as magnetic fields and their performance is compared with that of the viscoelastic core layer for the clamped-free boundary condition. Effects of core thickness, electric voltage and magnetic field on the vibration behavior of the sandwich box column are investigated.

This paper describes the application of semiactive devices for controlling the earthquake response of two highway bridges of different cross sections and pier heights. Each of the bridges consists of a three-span continuous deck supported on the piers and abutments. Semiactive devices such as the magnetorheological damper, the variable friction damper and the variable stiffness device are considered as the control devices. These devices are inserted between the deck and piers or abutments of the isolated bridge. The semiactive device changes its properties according to the structural response and adds control forces to the system. Each pier supporting the bridge is modeled as a linear lumped mass system. The optimum parametric values of the semiactive dampers are evaluated and considered in analysis of the bridge. A comparative study is performed for different semi-active devices installed on the bridges under different seismic loadings in the longitudinal direction. The behaviors of the bridges with different semiactive isolation devices are compared with the corresponding nonisolated ones. The semiactive dampers are observed as an effective protective device in reducing the displacements of the isolation bridges as well as the base shear of the piers.

In this paper, a beam element is derived for the thermal–dynamic coupling analysis by the updated Lagrangian formulation. The nodal transformation matrix of the element is obtained by dividing the rigid body rotation of the beam element into the relative translational displacements and axial rotation. With this transformation matrix, the interaction between the structural deformation and the absorbed heat flux can be formulated and the thermal–structural coupling effect is thus considered. The validity of the proposed method is illustrated by comparing the obtained results with the numerical, analytical or experimental results available in the literature. Then the method is employed to analyze the thermal–structural responses of the Hubble Space Telescope (HST) solar array. From the results, a reasonable explanation can be given for the failure of the telescope in 1990.

Based on the Maxwell equations, the electromagnetic constitutive relations and boundary condition, the electrodynamic equation and the electromagnetic force expressions in an electromagnetic field are derived. Using the principle of virtual work, the basic set of equations for nonlinear electromagnetic elasticity vibration expressed by the displacement of a thin plate in a longitudinal and a transverse magnetic field is obtained, respectively. In addition, we study the nonlinear principal resonance and the solution stability of a thin plate with two opposite sides simply supported and subjected to a mechanical live load and in a constant transverse magnetic field. By the method of multiple scales, the amplitude frequency response equation and the approximate analytic solution in steady motion are also derived. According to the characteristic of singularity and the Lyapunov stability theory, the stability of the solution is analyzed and the critical condition of stability is determined. Finally, by means of numerical calculations, the amplitude frequency response curves, time history response plots and phase charts of the magnetoelasticity vibration are obtained.

The large-amplitude free vibration problem of uniform slender pipes conveying fluid on a Pasternak foundation is studied using the principle of conservation of total energy. The temporal equation governing the large-amplitude vibrations is directly obtained from this approach by assuming a suitable admissible spatial function that satisfies the boundary conditions of the pipes. It is solved by using a standard numerical integration scheme. The numerical results, in the form of the ratio of the fundamental nonlinear frequency to the linear frequency for both the simply supported and clamped pipes conveying fluid, are presented in tables and figures for various amplitude parameters, flowing velocities of the internal fluid, and the two stiffness parameters of the Pasternak foundation.

This paper deals with the stability of the pylons of a cable-stayed bridge under the action of time-dependent loads, due to the vibration of the bridge deck. The stability of such problems of cable-stayed bridges is solved by a technique developed in the Laboratory of Metal Structures and Steel Bridges, of National Technical University of Athens (NTUA), as well as Bolotin's technique for the solution of nonlinear problems of dynamic stability. Three cases are studied: pylons with damping, pylons under forced vibration, and pylons subjected to an arbitrary external dynamic load. Useful relations are established by the aforementioned solution method, examples for a variety of pylons are presented, and interesting results regarding the stability of each case are given in diagrams.

This paper presents a highly accurate method for analyzing the critical shear buckling load of thin elastic rectangular plates. The solutions are approximated by the extended spline collocation method (SCM). Using the quintic table in place of the complex quintic B-spline functions, one can easily formulate the field equation of shear buckling loads for a thin elastic rectangular plate. Through the generalized eigenvalue analysis, the shear buckling loads and mode shapes for the plate can be determined precisely. Numerical examples are given for the critical shear buckling load of plates with various combinations of boundary conditions, aspect ratios, and uni- and bi-directional compressive/tensile loadings. The solutions obtained by the SCM are compared with those by the finite element method, the Lagrangian multiplier method, and the extended Kantorovich method under several types of boundary conditions. Compared with the other methods, the proposed SCM is not only more accurate, but also easier for computation.

This paper is concerned with the dynamic characteristics of composite beams with partial shear connections. The governing equations of motion for partial composite beams are derived from the one-dimensional partial composite beam theory. By solving the corresponding characteristic equation, the natural frequencies and modal shapes for simple partial composite beams are obtained. The orthogonality condition between the natural modes is utilized to decouple the equations of motion. Closed-form solution for the simple partial composite beam subjected to a moving load is derived by the modal superposition method. Key parameters that govern the fundamental frequency and deflection impact factor of simple partial composite beams are identified. Numerical results show that the former is controlled by the composite connection and section combination parameters, and the latter by the fundamental frequency ratio. It was observed that the time-history response of a partial composite beam may differ significantly from that of a full composite beam in terms of amplitude, period, and overall shape, depending on the composition connection.