International Journal of Structural Stability and Dynamics

Free vibration and buckling of laminated sandwich plate having soft core is studied by using an efficient C⁰ continuous finite element (FE) model based on higher-order zigzag theory (HOZT). In this theory, the in-plane displacement field for both the face sheets and the core is obtained by superposing a global cubically varying displacement field on a zigzag linearly varying displacement field with a different slope in each layer. The transverse displacement is assumed to be quadratic within the core while it remains constant in the faces beyond the core. The proposed model satisfies the condition of transverse shear stress continuity at the layer interfaces and the zero transverse shear stress condition at the top and bottom of the plate. The nodal field variables are chosen in an efficient manner to overcome the problem of C¹ continuity requirement of the transverse displacement. Numerical examples on free vibration and buckling covering different geometric and material features of laminated composite and sandwich plates are presented. Many new results are also presented which should be useful for future research.

The differential equation for inclined cables under axial narrow-band stochastic excitations is established with consideration of the cable sag and variations of cable tension along the cable. Gaussian and first-order non-Gaussian closed-form solutions are derived by employing the statistical moment truncation method to solve the moment equation. A long cable (Cable A20 of No. 2 Nanjing Bridge over the Yangtze River) is taken as an example to demonstrate the application of the theoretical model presented. The Monte Carlo method is also adopted to simulate the responses of the cable numerically under investigation. The general response characteristics of the cable are analyzed, particularly, the variation characteristics of the response of the cable depending on the excitation bandwidth when the ratio of the central frequency of excitation to the first frequency of cable is equal to one or two. Parametric vibrations of the real Cable A20 excited by the buffeting vibration of the bridge deck of No. 2 Nanjing Bridge over the Yangtze River are also calculated.

This study deals with the thermal buckling behavior of two-layer shear-deformable beams with partial interaction between the layers. The Timoshenko kinematics are considered for both layers and the shear connection is represented by a continuous relationship between the interface shear flow and the corresponding slip. Geometrically nonlinear behavior based on the von Kármán simplification of the Green strain tensor is accounted in the formulation. A set of differential equations is obtained from a general 2D bifurcation analysis using the aforementioned assumptions. The stability equations are obtained on the basis of the adjacent equilibrium criterion. It is shown that, due to the existence of the stretching–bending coupling effect in the composite beams, the bifurcation state occurs only for beams with both edges clamped.

Linear quadratic optimal regulator in multi-input setting exhibits several properties that are useful in adaptive control of structures. Its ability to preserve guaranteed stability margins in each input channel is particularly attractive to switch actuators, develop management schemes and meet the response tailoring objectives in the structure. A stabilizing controller for each of these actuators is already known from the regulator design. Since these controllers are infinite gain margin controllers, it is shown that they are also linear quadratic optimal with respect to a scalar multiplying the controller corresponding to the actuator. In this paper, these optimal controllers in a reconfigurable architecture are considered. Dynamic response tailoring by each actuator combination is investigated. Further, while switching actuators, parametric robustness of the reconfigurable systems is assessed with respect to the perturbed eigenvalues in a circular region. An oscillator model and a cantilever beam are used to illustrate the dynamic response tailoring in an adaptive structure using conventional and reconfigurable control principles.

Based on the nonlinear creep model and Kalker's linear theory, this paper studies the governing differential equations of motion for a tilting railway vehicle moving over irregular curved tracks under wind loads. The tilting vehicle is modeled by a 24-degree-of-freedom (24-DOF) car system, considering the lateral, roll and yaw motions of each wheelset, the lateral, vertical, roll and yaw motions of each bogie frame and the car body. The derailment quotients of the tilting railway vehicle with the wheelsets moving over irregular rails in the lateral direction and the car body acted upon by the wind loads are investigated for various tilting angles. The analysis results show that in general, the derailment quotient of the wheelset increases as the tilting angle of the railway vehicle increases. When the railway vehicle moves at low speeds, the derailment quotient calculated for the case with rail irregularities is greater than that for the case with no rail irregularities. Moreover, the derailment quotient of a wheelset moving over curved tracks of various radii is presented. Finally, the derailment quotient computed for the case under wind loads is greater than that free of wind loads. As a result, the influence of rail irregularities and wind loads on the derailment risk of a tilting vehicle cannot be ignored.

Currently, four grouped 177 m super-large cooling towers, i.e. column-supported hyperboloidal shells, are to be constructed in a typical electric power plant in Southeast China. To this end, simultaneous pressure measurements on 1:200 rigid tower models are carried out in an atmospheric boundary layer (ABL) wind tunnel, aimed at accurately obtaining the external/internal cladding wind loads on these shells. The wind-induced static behavior of the cooling towers is analyzed by applying the wind loads acquired via the pressure model tests, using both linear elastic and nonlinear elastic finite element (FE) analyses. The corresponding responses (structural deformation, internal force and local buckling state) are compared with those obtained by the traditional design approach, focused on the effects of internal suction and external pressure distribution. Besides, the tower group interference effects are studied by comparing the results computed of a freestanding tower, with those of the tower groups during two different construction stages. The main findings about the loading effects on the static performance of the super-large cooling towers are helpful for improving the current Chinese Codes that govern the design of super-large cooling towers.

This paper presents the stability analyses of glulam arches subjected to distributed vertical loading. The present analysis employs a strain-based formulation of a nonlinear geometrically exact three-dimensional beam theory. The influence of the relative height of the arch on the lateral buckling load is studied. The buckling load is determined by bisection method with observing the sign of the determinant of the tangent stiffness matrix. The post-critical load deflection path is traced by a modified arc–length method. Such influences are shown for arches with a constant cross-section or constant volume. After determining the most favorable height of the arch, the influence of the number and position of lateral supports is shown. We also compare the deflections, bending, and radial stresses at the lateral buckling states to the limit values which are recommended by European standards.

It has been found that the above article authored by Pengpeng Ni, includes works of Dr. António A. Correia from LNEC, Portugal, and Dr. Raffaele Figini from Enel Produzione, Ingegneria Civile e Idraulica, Milano, Italy (described in Secs. 2 and 3), and hence, Mr. Ni does not justify the publication with a single author name. This article was therefore, retracted from its publication in IJSSD. A statement of retraction is published in Int. J. Struct. Stab. Dyn., Volume 14, Issue 7 (2014) http://dx.doi.org/10.1142/S0219455414930018.

Higher-order multiple scales methods have been developed for a strong nonlinear differential equation modeling the nonlinear transverse dynamic behavior of piezoelectric–elastic–piezoelectric sandwich beams. The proportional and derivative potential feedback controls via sensor and actuator layers are used. Two higher-orders multiple scales methods are developed leading to accurate approximate time-response and frequency and phase-amplitude relationships. As the classical multiple scales method disregards the quadratic nonlinear terms, the developed higher-order multiple scales methods overcame this drawback and lead to more accurate results. Static and dynamic stability criteria are elaborated and tested. Critical bifurcation points and peak amplitudes are characterized in accordance with the excitation amplitude and the feedback parameters.

In the present work, computational methodologies based on artificial neural networks and genetic algorithms (GA) have been developed for identification of structural damage utilizing vibration data. The natural frequencies and mode shapes obtained from the finite element analysis for the first few modes have been considered for this purpose. A multi-stage hybrid methodology combining the modal strain energy criteria with GA has also been proposed, which showed improved damage identification capability as compared to the conventional GA, and proved to be computationally efficient. To demonstrate the efficiency of the proposed hybrid approach, numerical studies have been carried out on the truss structure. The efficacy of mode shape expansion in conjunction with GA is demonstrated for damage identification of reinforced concrete beam based on experimental modal data.

Critical buckling loads of composite laminates are usually calculated using analytical solutions based on the assumption of uniform in-plane loads, despite of the fact that real structures are often subjected to various nonuniform loads. The present work is focused on the buckling behavior of composite laminates, with and without cutouts, subjected to various nonuniform in-plane loads. The effect of the size of the cutouts, on the buckling behavior, has been studied using finite element method. Furthermore, parametric studies on the effects of plate aspect ratio, location of the cutout and the application of a nonuniform load combined with a shear load have also been studied. Higher buckling loads were observed in pure in-plane bending compared to uniformly/nonuniformly distributed loads. Consequently, it is important to consider nonuniformly distributed loading whenever applicable, to utilize complete strength of the composite laminate and to avoid premature failure of the composite laminate due to structural instability.

Free vibrations of straight beams which are partially supported by an elastic foundation are analyzed. For the sake of simplicity, only the Euler–Bernoulli beam model coupled with a Winkler-type elastic foundation is considered.

This structural system can be used to study, in a rather accurate way, the dynamic response of partially embedded piles (like those used for telecommunications) when dealing with the problem of identifying their mechanical properties during operative conditions.

The study makes clear that different kinds of vibration modes may occur in the part of the beam which is supported by the continuous elastic foundation: indeed apart from the classical modes, corresponding to the dynamics of a free beam, it is possible to have vibration modes which are similar to the static deflection of a beam on an elastic support or even corresponding to rigid-body modes. For the same beam it is shown that transition between these vibration modes can appear when switching from the fundamental natural frequency to subsequent ones. This effect is the focus of the presented numerical examples.

In particular, the analytic expression of the transcendental functions governing the vibration modes, and of the coefficients of the eigenfunctions for all occurring cases, are given here — to the best of the author's knowledge — for the first time.

From the practical point of view, the reported results allow to define a suitable range of the elastic stiffness parameter such that the behavior of a partially supported beam can be conveniently approximated with that of a single-span beam, having one built-in end and the other free.

This work investigates the implementation of nonlinear model reduction to flexible multibody dynamics. Linear elastic theory will lead to instability issues with rotating beam-like structures, due to the neglecting of the membrane-bending coupling on the beam cross-section. During the past decade, considerable efforts have been focused on the derivation of geometric nonlinear formulation based on nodal coordinates. In order to reduce the computation cost in flexible multibody dynamics, which is extremely important for complex large system simulations, modal reduction is usually implemented to a rotating flexible structure with geometric nonlinearities retained in the model.

In this work, a standard model reduction process based on matrix operation is developed, and the essential geometric stiffening nonlinearities are retained in the reduced model. The time responses of a tip point on a rotating Euler–Bernoulli blade are calculated based on two nonlinear reduced models. The first reduced model is derived by the standard matrix operation from a full finite element model and the second reduced model is obtained via the Galerkin method. The matrix operation model reduction process is validated through the comparison of the simulation results obtained from these two different reduced models.

An interesting phenomenon is observed in this work: In the nonlinear model, if only quadratic geometric stiffing term is retained, the two reduced models converge to the full finite element model with only one bending mode and two axial modes. While if both quadratic and cubic geometric stiffing terms are retained in the nonlinear equation, the modal-based reduced model will not converge to the finite element model unless all eigenmodes are retained, that is the reduced model has no degree of freedom reduction at all.