International Journal of Structural Stability and Dynamics

The imperfection sensitivity of cylindrical shells under external pressure is studied, focusing attention on tubes of considerable thickness, such as those to be employed for very deep water pipe lines or in some innovative nuclear power plant proposals. In such tubes collapse is dominated by yielding, but the decreasing nature of the post-collapse evolution makes the effects of interaction with instability significant enough to demand consideration. On the other hand, available theories assessing the imperfection sensitivity of thin shells do not apply in this context and empirical design formulas used for the medium-thick tubes typical of present oil industry applications are extremely conservative. The interaction phenomenon becomes inherently different as thickness increases, and its correct description appears a must in view of a rational assessment of the load bearing capacity. This paper is intended as a first step in this direction.

In this paper, a detailed analysis is conducted to study the influence of the geometric parameters, boundary conditions as well as initial imperfections on the nonlinear response and imperfection sensitivity of L-frames. An efficient nonlinear finite element formulation for the analysis of planar elastic frames is used together with incremental-iterative strategies. This enables one to obtain the highly nonlinear equilibrium paths exhibited by L-frames under certain loading conditions and identify the bifurcation and limit points along these equilibrium paths. These results provide some insight as to the source and mechanism of asymmetric bifurcation and imperfection sensitivity in frames thus helping engineers to evaluate the importance of geometric nonlinearities in the analysis and design of slender elastic frames.

In this paper we consider the longitudinal vibrations of bimodular rods. After proving the equivalence between the entropy condition and Lax condition (whenever this latter is applicable), we go on to consider the Riemann problem and prove that a unique solution always exists except for the special case of no-tension materials. This procedure allows for easy determination of the explicit solution.

Thermally-induced transverse displacement of unidirectional ply, cross-ply and anti-symmetric angle-ply composite plate is investigated. The laminates are assumed to be simply supported along the four edges. The dynamic flexural response due to sudden surface heating is examined, with emphasis on the effects of plate thickness and stacking sequence on the maximum plate deflection of a graphite-epoxy composite. The total displacement is obtained by superposition of the first mode quasi-static and dynamic solutions. The quasi-static displacement is derived using a Levy-type solution while the dynamic displacement is formulated by utilizing the Classical Lamination Theory (CLT), Galerkin's Method and the Laplace Transform. The results show that thermally-induced displacements in unidirectional and cross-ply laminates for the same thickness are far less than those in angle-ply laminates.

The present paper is concerned with the vibration, buckling and dynamic instability behavior of laminated composite, cross-ply, doubly-curved panels with a central circular hole subjected to in-plane static and periodic compressive loads. A generalized shear deformable Sanders' theory is used to model the curved panels, considering the effects of transverse shear deformation and rotary inertia. Bolotin's approach is used for studying the dynamic instability regions of doubly-curved panels. The effects of non-uniform edge loads, curvature with different cutout ratios, static and dynamic load factors, and lamination parameters on curved panels are investigated with the results discussed.

This paper shows the existence of a class of horizontal setback buildings that exhibits (i) existence of two distinct types of mode, e.g., rigid floor mode and flexible floor mode, (ii) zero participation of flexible floor modes under spatially uniform ground motion, and (iii) zero participation of torsional modes. Such a class of buildings is referred herein as proportionate dynamically non-separable (PDNS) buildings. PDNS class differs from the existing concept of dynamically separable building in two respects. First, PDNS class does not impose any condition over the floor properties. Second, the eigen properties of the frames along one orthogonal direction may be different from that along other orthogonal directions. Therefore, PDNS class provides a wider latitude in modeling a building so as to minimize the effect of in-plane flexibility of the floor diaphragm. The existence of such buildings is shown in the form of horizontal setback buildings with all the wings oriented along the orthogonal directions (e.g., L, T, and + shapes).

In this technical note, the post-buckling behavior of a simply supported elastic column with various rotational end conditions of the supports is investigated. The compressive force is applied at the tip of the column. The characteristic equation for solving the critical loads is obtained from the boundary value problem of linear systems. In the post-buckling state, a set of nonlinear differential equations with boundary conditions is established and numerically solved by the shooting method. The interesting features associated with this problem such as the limit load point, snap-through phenomenon and the secondary bifurcation point will be highlighted herein.

This technical note presents the solution for flutter instability of a piezoelectric layer subjected to an external voltage which can be modeled as a compressive follower force. The critical ratio of the length to the thickness of the piezoelectric layer for the possible flutter instability is derived given the endurable electric field of the piezoelectric material. The calculation is conducted for piezoelectric layers which are both free and surface bonded on a host structure. Numerical simulations are conducted for the possible flutter instability of different PZT (Lead Zirconium Titanate) materials. The findings in this study should serve as useful benchmarks for the stability analysis of piezoelectric materials.

This study investigates the error which occurs when numerically integrating the equation of motion of a single degree of freedom system excited by a harmonic force near resonance. The Constant Average Acceleration method was considered in particular as it features in many finite element software packages. It was found that a considerable error in the calculated responses occurs in systems with low damping due to the well known phenomenon of period elongation. However, the error is reduced for systems with higher damping and/or when smaller time step is used. With regard to this, recommendations are given as to the time steps required to obtain solutions with a pre-defined level of accuracy.