Showing papers on "Critical load published in 1989"
TL;DR: In this paper, the buckling analysis of rectangular composite laminates with circular holes under inplane static loadings was studied, where the first-order shear deformation theory and the variational energy method were employed in mathematical formulation, and the ninenode Lagrangian finite element method was used for finding critical loads.
Abstract: This paper deals with buckling analysis of rectangular composite laminates with circular holes under inplane static loadings. The first-order shear deformation theory and the variational energy method are employed in mathematical formulation, and the nine-node Lagrangian finite element method is used for finding critical loads. The effects on critical load by hole size, plate thickness ratio, material modulus ratio, ply lamination geometry, loading types, and boundary conditions are investigated. Numerical solutions are shown in graphical form where some comparisons are made with those of given litera tures.
95 citations
TL;DR: In this article, a study of the growth of delamination due to bending in a [905/05/905] graphite/epoxy laminate is presented, where a plane strain finite element analysis is used to determine the strain energy release rate during delamination in a three-point-bend specimen.
48 citations
TL;DR: In this article, a comprehensive non-linear stability analysis has been performed on an one-degree-of-freedom arch for establishing its dynamic (elastic) snap-through buckling strength under impact loading.
30 citations
TL;DR: In this paper, Mollmann and Goltermann studied the mode interaction between local and global buckling modes for two types of thin-walled beam structures, using a method of analysis presented in Part I of the author's paper.
30 citations
TL;DR: In this article, a procedure based on the limit stability condition of longitudinal reinforcing bars is proposed for the calculation of the ultimate strain of compressed concrete elements, and an approximate analytical expression is given to be used in practical ductility calculations.
Abstract: For the calculation of the ultimate strain of compressed concrete elements, a procedure is proposed that is based on the limit stability condition of longitudinal reinforcing bars. The analysis model is the one proposed in Papia et al. (1988), which provides the critical load of the bar with reasonable accuracy. Analogous precision in the values of the critical strain of the longitudinal reinforcement, assumed to coincide with the ultimate strain of the concrete element, is obtained here by not assuming a constant elastic modulus in the strain hardening region of the steel, and by adopting for the latter the constitutive link given in Park and Paulay (1975). The problem is reduced to the solution of an equation in the unknown strain, which depends on the slenderness of the bar of length equal to the spacing of hoops, and on the hoop stiffness. The most widely used steels are then considered with the variations in the parameters indicated above. On the basis of the results obtained, an approximate analytical expression is given of the ultimate strain to be used in practical ductility calculations. A comparison to the experimental results obtained by other authors confirms the validity of the theoretical approach proposed.
29 citations
TL;DR: In this article, the cylindrical buckling load of a composite laminated column is derived from plate theory and the effect of lamina orientation is taken into account by treating the stiffness parameter as a matrix product rather than as a single value drawn from the definition of the elastic coefficients.
Abstract: The cylindrical buckling load of a composite laminated column is derived from plate theory. The effect of lamina orientation is taken into account by treating the stiffness parameter as a matrix product rather than as a single value drawn from the definition of the elastic coefficients. This refined stiffness parameter leads to significant improvement of the buckling load, depending on the stacking combination and orientation.
15 citations
TL;DR: In this paper, the influence of weakening or a crack at an edge on the critical buckling load of a variety of single and multilayered shells was investigated and it was shown that isotropic shells exhibit a rather sudden steep reduction in the critical load for relatively small edge damage.
Abstract: The influence of weakening or a crack at an edge on the critical buckling load of a variety of single and multilayered shells is investigated. Results indicate that isotropic shells exhibit a rather sudden steep reduction in the critical buckling load for relatively small edge damage
12 citations
TL;DR: In this paper, the authors present minimum-weight designs of plane structural frames under multiple load systems, each load system consists of external concentrated and distributed loads, couples and self-weight, and the optimization problem reduces to a nonlinear programming problem whose solution is attempted by several methods.
11 citations
TL;DR: In this article, the authors established a general relation defining the critical state produced by simultaneous action of loads differing in their nature and effect, and established some particular relationships which have been experimentally verified for critical groups of loads.
8 citations
TL;DR: In this article, a nonlinear analysis of plane, non-orthogonal frames with flexible joint connections and with elastic rotational restraints at the supports, under static and dynamic loads is presented.
7 citations
TL;DR: In this article, the critical load capacity of various slider bearings with different surface topographies is calculated and measured, and the experimental results for the different specimens are similar to those predicted by the computer simulation.
TL;DR: In this article, the instability of a shallow arch subjected to random loading is investigated, where the authors examined the effects of the spatial distribution of the load, the load intensity, the mean load, damping magnitude, the arch height and the inclusion of multiple response modes.
TL;DR: In this article, the shape determination problem of the cantilever column, subjected to the follower force, was solved by maximizing the critical load under constraints of volume constancy and lower limit of design variables, under the influence of internal and external damping.
Abstract: This paper deals with the shape determination problem of the cantilever column, i. e. Beck's column, subjected to the follower force. The objective is to maximize the critical load under constraints of volume constancy and lower limit of design variables, under the influence of internal and external damping. The governing equation of motion is transformed into a matrix system by the finite element method with the adjoint variational principle based on the Lagrange multiplier method. The shape improvement process is formulated by the gradient projection method based on the sensitivity of critical load to the design. Numerical results show that improved shape has a higher critical load than the initial shape (uniform) and makes three eigenvalues achieve a critical point simultaneously.
TL;DR: In this paper, the failure mechanism of cylinders with an IRN/N/It/N ratio equal to 250 was numerically investigated under transverse shear and the effects of geometric imperfections and initial stresses due to manufacturing procedures (cold bending and welding) were considered.
Abstract: In this study the failure mechanism of cylinders with an \IR\N/\It\N ratio equal to 250 is numerically investigated under transverse shear. The effects of geometric imperfections and initial stresses due to manufacturing procedures (cold bending and welding) are considered. Seven models, consisting of combinations of different degrees and patterns of imperfections and residual stresses, are analyzed. All the models lose their stability by buckling in a shear mode. The influence of imperfection on the magnitude of critical load is moderate. By contrast, the locked-in stress induced in the shell by the manufacturing procedures proves to have a large influence on the magnitude of the critical load. In the postbuckling range, a stable equilibrium path is reached by all models at a lower load level than the initial load. The carrying mechanism at this level resembles a truss with tension diagonals and inclined compressive struts.
01 Dec 1989
TL;DR: In this paper, the static response of a circular cylindrical open shell (curved panel) constructed of an orthotropic graphite/epoxy laminate is numerically investigated, where the shell is subjected to an inward point load, centered on and normal to the shell surface.
Abstract: : The static response of a circular cylindrical open shell (curved panel) constructed of an orthotropic graphite/epoxy laminate is numerically investigated in this thesis. The shell is subjected to an inward point load, centered on and normal to the shell surface, which maintains its original orientation through deformation (i.e. dead load). The shell displacement response is seen to vary widely with shell geometry and boundary conditions, not only in magnitude of deformation but also in the nature and progression of the collapse under critical load. The finite element analysis is conducted with a quasi-two dimensional thin shell element which incorporates parabolic transverse shear stress through the thickness. The element can be formulated with either large displacement/rotation kinematics or the simpler Donnell relations. To enable tracking through critical load and displacement points and investigation of the post-critical regime, a solution algorithm other than the popular Newton- Raphson technique with displacement control or load control is required. The algorithm employed here uses a modified Riks/Wempner technique. It allows continuous tracing of the load - deflection response through critical load and critical displacement points. Step size is automatically scaled to follow the solution path closely in the areas of large load or displacement changes which surround critical points. (KR)
01 Jan 1989
TL;DR: In this article, the regionalized RAINS Lake Model (RLM) is used to construct a target load for Finnish lake regions. But the model was driven with alternative low deposition patterns, starting from the combined pH-alkalinity frequency distributions in 1980, and the output information was then interpreted with respect to critical and target loads.
Abstract: ‘Critical load’ is defined as “an inherent property of a system” being the highest load that will not cause harmful effects on essential ecosystem properties. There is a gradual deterioration of surface water ecosystems with the successive process of acidification. Therefore, the definition of the criteria for what might be considered as harmful is largely a matter of subjective decision. A number of studies have indicated that acidic deposition should be pushed below background values in order to protect every single most sensitive stream or lake. This is in practice not possible and therefore not a feasible goal. The decision as to whether to protect all but some of the most sensitive surface waters or to choose some other level of environmental damage as acceptable has a significant effect on the load to be chosen. The term related to political decisions is ‘target load’ which may be either greater or smaller than the critical load for the same system. In this chapter, the regionalized RAINS Lake Model (RLM) is used to construct a target load for Finnish lake regions. The model was driven with alternative low deposition patterns, starting from the combined pH-alkalinity frequency distributions in 1980. As an output the model runs produce a frequency distribution of pH and alkalinity for the selected deposition scenario and year. The output information is then interpreted with respect to critical and target loads. The model results indicate that in order to protect the most sensitive ecological system, the critical load of sulfur for the southern parts of Finland is very close to zero, between 0.0 and 0.1 gSm−2 yr−1. The target load can be stated to have values anywhere above 0.1 gSm−2 yr−1 depending on the sensitivity of the region and on the most approriate level of protection.
01 Jan 1989
TL;DR: In this article, an elastic-buckling and postbuckling analysis of an axially loaded column with an across-the-width delamination, symmetrically located at an arbitrary depth, is presented.
Abstract: An elastic-buckling and post-buckling analysis of an axially loaded column with an across-the-width delamination, symmetrically located at an arbitrary depth, is presented. Using the perturbation technique, analytical solutions for the critical buckling load and the post-buckling deflections are obtained. All possible instability modes, namely, local delamination buckling, global column buckling and coupled global and local buckling are considered
TL;DR: In this paper, the minimum critical load of the lateral buckling occurring on under a concentrated force, uniformly distributed load and the concentrated couples, respectively, was discussed, and the energy method was used in this article.
Abstract: This paper investigates the problems of lateral buckling of rectangular plates In the text we discuss the minimum critical load of the lateral buckling occurring on under a concentrated force, uniformly distributed load and the concentrated couples, respectively The energy method is used in this article
TL;DR: In this article, the authors examined the applicability of the Southwell method to predict the buckling load of columns where the shear deformation cannot be neglected and showed that the convergence of the series solution is slow, since there are two critical loads of the same order associated with the first mode shape for rotation of the cross section.
Abstract: This paper examines the applicability of the Southwell method to predict the buckling load of columns where the shear deformation cannot be neglected. It is shown by mode superposition that the convergence of the series solution to the buckling mode is slow, since there are two critical loads of the same order associated with the first mode shape for rotation of the cross section. More important, the Southwell plot is not linear even when only one mode shape (corresponding to the lowest critical load in compression) is considered. An example of numerical simulation demonstrates that linearly fitting the Southwell plot can lead to significant errors in the prediction of the buckling load. The accuracy of buckling load determined by the Southwell method for typical elastomeric isolation bearings is also discussed.
TL;DR: In this article, a built-up sandwich beam is modeled by two thin elastica of facing material affixed to a series of equally spaced rigid separation blocks, and large deformation equations under pure bending are formulated and solved by perturbations and numerical integrations.
01 Jan 1989
TL;DR: In this article, a theory of delayed crack instability of viscoelastic bodies is outlined and applied to concrete, and several rheologic models are recommended for the description of concrete.
Abstract: A theory of delayed crack instability of viscoelastic bodies is outlined and is applied to concrete in this paper. Several rheologic models are recommended for the description of concrete. An approach for determining critical load or crack size or critical time for delayed crack instability is proposed.
TL;DR: In this paper, the minimum critical load of rectangular plates which possess the unsymmetrical supporters and to which the lateral buckling occurs under a concentrated force, uniformly distributed load and the concentrated couples respectively are discussed.
Abstract: The present paper investigates several problems for unsymmetrically lateral instability of rectangular plates by the energy method. In the text we discuss the minimum critical load of rectangular plates which possess the unsymmetrical supporters and to which the lateral buckling occurs unsymmetrically under a concentrated force, uniformly distributed load and the concentrated couples respectively.
01 Jan 1989
TL;DR: In this article, the question of elastic stability of a shell arises, just as it does in plates and columns, which were discussed in Chapter 7, and it is discussed in Section 2.
Abstract: Over and above the determination of stresses and displacements in shell structures, under some loadings the question of elastic stability of a shell arises, just as it does in plates and columns, which were discussed in Chapter 7.
01 Jan 1989
TL;DR: In this article, an extended review of results previously obtained by the authors, supplemented by some new results dealing with the optimal segmentation of columns is presented, with particular attention paid to the optimal support location as well as the elastic, viscous and dynamical parameters of the supporting elements.
Abstract: Present paper is an extended review of results previously obtained by the authors, supplemented by some new results dealing with the optimal segmentation of columns. Particular attention is paid to the optimal support location as well as the elastic, viscous and dynamical parameters of the supporting elements. Since the resulting boundary value problem is non-selfadjoint and a switch-over effect of the characteristic curves may occur, generally only local optimization is possible. To solve the problem, a certain gra-dient procedure combined with the transfer matrix technique has been used. Such a pro-cedure relies on minimizing the cost functional for a given value of the critical load or maximizing the load if the total cost is given. Some generalizations of Beck-Reut’s problem are investigated.
01 Jan 1989
TL;DR: In this paper, a pin-ended circular arch subjected to a concentrated vertical load at an arbitrary point between the center and end is analyzed numerically and experimentally for asymmetric snap-through buckling behavior.
Abstract: Asymmetric snap-through buckling behavior of elastic plastic arches is analyzed numerically and experimentally. The numerical analysis with a discrete model composed of rigid bars and nonlinear springs is carried out for a pin-ended circular arch subjected to a concentrated vertical load at an arbitrary point between the center and end. A power hardening law is assumed for plastic loading and the kinematic hardening rule is pstulated for reversed yield, which may appear during snap-through. The critical load and the lcad4eflection curve in the post-hckling range have been ccmpared for symmetric and asymmetric buckling. It was shown that the minimum of the critical load in asymmetric buckling is about 213 of that in symetric me. Deflection-controlled buckling experiment of a mdel arch has revealed variations of the vertical load and thrust during snap-thorough process and has confirmed the validity of the present numerical analysis. The conventional analysis neglecting reversed plasticity is found to give significantly smaller deflection than the experiment in the later stage of snap-through.