Stability Of Elastic Structures Research Articles

Interactions between tetracycline and extracellular polymeric substances in anammox granular sludge

The effects of antibiotics on extracellular polymeric substances (EPS) using tetracycline as the model chemical were analyzed in terms of molecular property and structure. Results showed that three components, tryptophan, tryptophan type-proteins and polysaccharides in EPS of granular sludge from anaerobic ammonium oxidation (anammox) reactor can interacted with tetracycline, detected by the static quenching via the endogenous fluorescence quenching and transient fluorescence spectroscopy. Thermodynamic experiment confirmed that their interaction was dominated by the hydrophobic force. Combined with the synchronous fluorescence spectroscopy, it was found that tetracycline facilitated the extension degree of peptide chains in tryptophan type-proteins, leading to the enhancement of hydrodynamic diameter of the macromolecules in EPS when binding with tetracycline. EPS in AnGS demonstrated the resistance ability to tetracycline by converting from gel to sol state in rheological term. With the increase of tetracycline concentration, the stability of elastic structures in EPS declined, influencing the AnGS stability.

The dynamics and stability of circular cylindrical shells containing and submerged in flowing fluid using a higher order boundary element method

This paper presents a higher order, three-dimensional boundary element method for investigating the dynamics and stability of elastic structures containing and/or submerged in flowing fluid. The method developed can be applied to any shape of elastic structures partially or completely in contact with fluid. In the mathematical model, it is assumed that the fluid is ideal (i.e. inviscid, incompressible and its motion is irrotational). The fluid—structure interaction forces are calculated using the higher order boundary element method, and the finite element method is employed for the structural analysis. In this study, it is assumed that the elastic structure vibrates in its in vacuo modes when it is in contact with flowing fluid, and that each mode gives rise to a corresponding surface pressure distribution on the wetted surface of the structure. The in vacuo dynamic properties of the dry elastic structure are obtained by using standard finite element software. In the wet part of the analysis, the wetted surface of the elastic structure is idealized by using appropriate boundary elements, referred to as hydrodynamic panels. Over each hydrodynamic panel, higher order distributions (linear and quadratic) are adopted in the present study in order to obtain a better convergence, in contrast to Ugurlu and Ergin (2006) assuming constant distribution over each hydrodynamic panel. The fluid—structure interaction forces are calculated in terms of the generalized added mass coefficients, generalized Coriolis fluid force coefficients, and generalized centrifugal fluid force coefficients. To assess the influence of flowing fluid and end support conditions (e.g. simply supported ends, clamped ends, and cantilever cylindrical shell) on the dynamic response behaviour and stability of the cylindrical shells, the non-dimensional wet frequencies and associated vibration modes are presented as a function of the non-dimensional axial flow velocity, and the calculations compare well with the analytical solutions found in the open literature.

Structural stability and failure analysis using peridynamic theory

The peridynamic theory has been successfully utilized for damage prediction in many problems. However, the elastic stability of structures has not been studied using the peridynamic theory. Therefore, this paper investigates the elastic stability of simple structures to determine buckling characteristics of the peridynamic theory by considering two sets of problems. The first set of problems involves rectangular columns under compression to find the effects of the cross-sectional area and boundary conditions on buckling load. The second set involves rectangular plates under a uniform temperature load to establish the effects of plate dimensions and material properties on the critical buckling temperature. The predictions of the peridynamic theory agree with those published in the literature. The solution method is based on reducing the peridynamic equations of motion to discrete forms by using collocation points. These discrete equations are then solved using adaptive dynamic relaxation. Furthermore, perturbation method using geometrical imperfections is utilized to trigger lateral displacements in the numerical solutions.

Book Review: Stability of Elastic Structures. By N. A. Alfutov

Book Review: Stability of Elastic Structures. By N. A. Alfutov

Stability of Elastic Structures. Foundations of Engineering Mechanics

Stability of Elastic Structures. Foundations of Engineering Mechanics

Non-Classical Problems in the Theory of Elastic Stability

9R18. Non-Classical Problems in the Theory of Elastic Stability. - E Elishakoff (Dept of Mech Eng. Florida Atlantic Univ, Boca Raton FL 33431-0991), Y Li (Alpine Engineered Prod), and JH Starnes Jr (Struct Mech Branch, NASA Langley Res Center, Hampton VA 23665). Cambridge UP, New York, 2001. 336 pp. ISBN 0-521-78210-4. $85.00.Reviewed by JA Cheney (Dept of Civil and Env Eng. UC, Davis CA 95616).This monograph presents two competing yet complementary theories which incorporate ever-present uncertainty in the stability of elastic structures in the real world. These uncertainties are first and foremost due to unavoidable initial imperfections, deviations of the structure from its intended, nominal, ideal shape. Other uncertainties are in material properties and/or realizations of the boundary conditions. These considerations are addressed by a unified probabilistic theory of stability and the alternative, based on the notion of anti-optimization, that is useful when the necessary information for probabilistic analysis is absent. The book is non-classical in the sense that it goes beyond deterministic methods to probabalistic and set-theory approaches to the buckling of structures. The first two chapters are devoted to some new deterministic problems in local buckling of multispan plates and columns and the influence of thickness variation of perfect or imperfect, isotropic or composite, circular cylindrical shells. Chapters 3 and 4 deal with stochastic buckling of structures with random imperfections. Chapter 3 uses the Monte Carlo technique while Chapter 4 discusses approximate analytical and numerical techniques, including the asymptotic analysis, the first-order second moment method, the mode localization due to random displacements, and the finite element method for structures with random material properties. What is called convex modeling of uncertainty in buckling problems is presented in Chapter 5 wherein data scarcity and uncertain material properties are involved in an ensemble of plates and shells. Chapter 6 discusses the Godunov-Conte shooting method, and Chapter 7 deals with the applications of computerized symbolic algebra. The treatment is scholarly, having about 900 items in the bibliography and additional contributors in the writing of almost every chapter. In addition to the extensive bibliography, an author index of those referenced in the text and a subject index are included. This reviewer believes that Non-Classical Problems in the Theory of Elastic Stability should be a useful reference for researchers, engineers, and graduate students in aeronautical, mechanical, civil, nuclear, and marine engineering, and in applied mechanics.

Imperfection Sensitivity at Near-Coincidence of Two Critical Points∗

ABSTRACT Elastic stability of structures with finite degrees of freedom is analyzed. The two smallest critical values of the load parameter are supposed to be equal or nearly equal. The effect of imperfections on the distance between critical values is considered. Using the results of catastrophe theory, imperfections are determined at which the structure looses its stability before reaching a prescribed value of the load parameter.

Stability of Lattice Structures Under Combined Loads

The stability of elastic structures under multiple independent loads is considered. Interaction effects of the independent loading parameters are examined in terms of stability boundaries, which separate regions of stable and unstable load combinations in the load space. The convexity properties of these stability boundaries are discussed in general, both for linear and nonlinear systems. A reticulated dome subjected to vertical loads is then analyzed numerically. The dome exhibits nonlinear prebuckling deformations. Static perturbation and nonlinear programming methods are utilized to compute buckling loads. Results are presented for two and three independent load configurations, and the characteristics of the stability boundaries are discussed. Finally, the interactions for the reticulated dome are compared to those for shallow arches.

Numerical methods for elastic structural stability analysis

Abstract The Gauss-Seidel, the successive overrelaxation, the conjugate gradient, the Cholesky's square root and the Cholesky's decomposition methods for solving systems of linear algebraic equations encountered in structural analysis are considered. Theorems for these methods establishing necessary and sufficient conditions for the matrix of the coefficients to be positive definite are converted into criteria for elastic structural stability. Numerical procedures, by using these methods in conjunction with their corresponding stability criteria, for checking the elastic stability and determining the elastic critical load of a structure are proposed. Application of these procedures to the stability analysis of plane frameworks leads to the conclusion that the proposed direct schemes are more efficient than the iterative ones.

Stability of elastic structures in controlled flight

Stability of elastic structures in controlled flight

Fundamental principles in the buckling of structures under combined loading

The basic concepts of the general theory of elastic stability are developed with reference to combined loading, only discrete conservative structural systems being considered.It is observed that the two well known critical points, the limit and bifurcation points, are not quite adequate to describe the buckling behaviour of structures under combined loading. A more appropriate classification which describes the nature of buckling more aptly is given. Thus, in the elastic stability of structures under combined loading, mainly two types of critical point are involved, the “general” and “special” critical points. The conditions giving rise to these two distinct phenomena and their relation to the limit and bifurcation points are examined in detail. The connexion between the shape of the equilibrium surface and the nature of buckling is demonstrated analytically.

A basis for the linear theory of elastic stability of structures

In this paper a consistent linear theory of stability of elastic structures is given and the problem of the neutral equilibrium of a continuum composed by an elastic material with high stiffness to the strains is studied. All the particular cases, as the buckling of beams, plates, shells etc., ensue and their classification in regard of their significance is given. There are comparisons with other theories.

Dynamic stability of elastic structure in controlled flight at supersonic speed

Dynamic stability of elastic structure in controlled flight at supersonic speed