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Copyright of Gazi Journal of Engineering Sciences (GJES) / Gazi Mühendislik Bilimleri Dergisi is the property of Gazi Journal of Engineering Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present work aims to study the elastoplastic buckling, postbuckling, and failure behavior of perforated Ni/Al2O3functionally graded material (FGM) plate with various shaped cutouts (i.e., circular, square, diamond, and elliptical) of various sizes under thermomechanical loading conditions using finite element method (FEM). The nonlinear FEM formulation is based on the first-order shear deformation theory and von Kármán’s nonlinear kinematics in which the material nonlinearity is incorporated. The nonlinear temperature-dependent thermoelastic material properties of FGM plate are varied in the thickness direction by controlling the volume fraction of the constituent materials (i.e., ceramic and metal) as per a power law, and Mori–Tanaka homogenization scheme is applied to evaluate the properties at a particular thickness coordinate of FGM. In accordance with the Tamura–Tomota–Ozawa model (TTO model), the ceramic phase of FGM is considered to be elastic, whereas the metal phase is assumed to be elastoplastic. Further, the elastoplastic analysis of FGM is assumed to followJ2plasticity with isotropic hardening. After validating the present formulation with the results available in the literature, various numerical studies are conducted to examine the effects of material inhomogeneity, thermal loading, cutout shape, and size on the elastoplastic buckling, postbuckling, and failure behavior of perforated FGM plate. It is observed that for smaller cutout sizes, the FGM plate with square shape cutout possesses maximum value of ultimate failure load; however, for larger cutout size, the FGM plate with diamond cutout depicts highest ultimate failure load. Furthermore, for all cutout shapes, the ultimate failure load of FGM plate decreases with an increase in cutout size. It is also revealed that irrespective of shape and size of cutout, the material plastic flow has considerable effect on postbuckling path of FGM plate, and under thermomechanical loading conditions, the FGM plate shows destabilizing response after the point of maximum postbuckling strength. [ABSTRACT FROM AUTHOR]

A numerical study is carried out using finite element method, to examine the effects of square and rectangular cutout on the buckling behavior of a sixteen ply quasi-isotropic graphite/epoxy symmetrically laminated rectangular composite plate [0°/+45°/-45°/90°] subjected to various linearly varying in-plane compressive loads. Further, this paper addresses the effects of size of square/rectangular cutout, orientation of square/rectangular cutout, plate aspect ratio(a/b), plate length/thickness ratio(a/t), boundary conditions on the buckling bahaviour of symmetrically laminated rectangular composite plates subjected to various linearly varying in-plane compressive loading. It is observed that the various linearly varying in-plane loads and boundary conditions have a substantial influence on buckling strength of rectangular composite plate with square/rectangular cutout. [ABSTRACT FROM AUTHOR]

In this paper, a Levy-type solution based on the modified couple stress theory is developed to study the buckling behaviors of micro-plates. Based on this theory, length scale parameter is considered to capture the size effect of rectangular micro-plates. Minimum potential energy and adjacent-equilibrium criteria are exploited to obtain the stability equations and corresponding boundary conditions. Different boundary conditions with two opposite edges simply supported and arbitrary boundary conditions along the other edges are considered. To illustrate the new model, both uniaxial and biaxial loads are applied and the critical buckling loads are defined for over a wide range of thickness, different length scale parameters and various boundary conditions. To show the accuracy of the formulations, present results are compared with available results in literature for specific cases and a very good agreement is observed. Results reveal that the critical buckling load increases as the length scale parameter increases especially when the thickness of the micro-plates becomes in order of length scale parameter and this effect is more significant for free boundary condition. [ABSTRACT FROM AUTHOR]

This paper focuses on the effect of member geometric imperfection on nonlinear geometrically buckling and seismic performance of a new style of space steel structure, suspen-dome, which is composed of a reticulated shell and cable-strut system. By supposing the initial curvature of members as half-wave sinusoids, a stiffness equation of imperfect truss elements is derived for the struts, while that of imperfect beam elements is derived for the reticulated shell members. The proposed imperfect elements are implanted into ANSYS finite element program. Three numerical examples are employed to validate the proposed imperfect elements and analysis method. An ellipsoidal suspen-dome of Changzhou gymnasium is taken as an example. The results show that the imperfection value has relatively great influence on the structural stiffness. With the increase of member imperfection, the critical load decreases in a basically linear way. Under different prestress states, the relation curves between the critical load and imperfection are basically parallel. The nonlinear seismic analysis results show that when imperfection is included, the initial state responses are different, namely, the seismic displacement increases while the stress in rods and cables decreases. The proposed imperfection analysis method can be widely used in not only suspen-dome structures, but also other kinds of prestressed space grid structures. In this way, the influence of member imperfection on structural buckling and seismic performance can be estimated. [ABSTRACT FROM AUTHOR]

In structural stability analyses, determining the critical buckling load is a crucial issue. Regression, fuzzy logic and Artificial Neural Network (ANN) algorithms can be used to determine critical buckling loads. This study compares the results of different approaches for column buckling load prediction. Regression, Fuzzy logic and ANN algorithms were employed in the analyses, representing material properties to take uncertainties into account and the results were compared. The results show that uncertainties play an important role in stability analyses and should be considered in the design. The elastic modulus results predicted by regression, fuzzy logic and ANN are also compared to those obtained using empirical results of the buildings codes and various models. These comparisons show that obtained results in the present study give closer results than the different design codes. Therefore, proposed models can be used for critical buckling loads and regression, fuzzy logic and ANN have strong potential as a feasible tool for estimating column buckling loads within the range of input parameters considered. [ABSTRACT FROM AUTHOR]

The presence of in-plane loading may cause buckling of stiffened panels. An accurate knowledge of critical buckling load and mode shapes is essential for reliable and lightweight structural design. This paper presents parametric studies on simply supported laminated composite blade-stiffened panels subjected to linearly varying in-plane edge/compressive loading. Studies are carried out by changing the panel orthotropy ratio, stiffener depth, pitch length (number of stiffeners), smeared extensional stiffness ratio of stiffener to that of the plate and load distribution parameter. Based on the studies, a few important parameters influencing the buckling behavior are identified and their significance is discussed. Further, the interaction equations for combined loadings are validated by carrying out numerical studies. [ABSTRACT FROM PUBLISHER]

The solution of the buckling problem for a rectangular composite sandwich plate with two parallel simply supported edges and another two edges clamped (SSCC) is presented in the paper. The plate is composed of two identical composite facings and orthotropic core, and subjected to in-plane uniform compressive load applied to the simply supported edges. Buckling equations are derived based on the first-order shear deformation theory. The problem is solved using the Levy and Galerkin methods. The analytical formula for the critical load has been obtained and verified using finite-element analysis. The design analyses have been performed for the sandwich panels subject to constraints imposed on the value of buckling load. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

It is illustrated in this paper that a nonlinearly elastic column, depending upon the values of different material parameters involved, exhibits several stability characteristics and types of buckling which are generally observed separately in distinctively different structural systems. By introducing finite disturbances it is shown that the column may buckle well before the bifurcation buckling load is reached. The proposed approach can be useful in engineering practice since it can be utilized to study the stability of uniaxial structural elements made from rubber or any other material which obeys the modified Ludwick's constitutive model. [ABSTRACT FROM AUTHOR]

This paper presents a method and procedure of sensing and determining critical shear buckling load and corresponding deformations of a comparably large composite I-section using strain rosettes and displacement sensors. The tested specimen was a pultruded composite beam made of vinyl ester resin, E-glass and carbon fibers. Various coupon tests were performed before the shear buckling test to obtain fundamental material properties of the I-section. In order to sensitively detect shear buckling of the tested I-section, twenty strain rosettes and eight displacement sensors were applied and attached on the web and flange surfaces. An asymmetric four-point bending loading scheme was utilized for the test. The loading scheme resulted a high shear and almost zero moment condition at the center of the web panel. The web shear buckling load was determined after analyzing the obtained test data from strain rosettes and displacement sensors. Finite element analysis was also performed to verify the experimental results and to support the discussed experimental approach. [ABSTRACT FROM AUTHOR]

This work presents the milestones of the underlying of a patented work [1] (Abdul-Latif, 2014) which aims to enhance the plastic buckling resistance of thin-walled right-circular cylindrical mild steel tubes deformed axially under the quasi-static compressive load. The proposed concept can be described by producing a metal like-composite where a hard phase incorporates in these tubes made by case-hardening of 15% of tubes outer surface with different geometrical shapes and a constant depth along the tubes thickness. To study the effect of case-hardening configurations, several forms were designed, made and tested. They were four ring forms (with 2, 3, 4 and 5 rings), two vertical strip forms (2 and 3 strips) and, six helical strip forms with three tilt angles of 30°, 45° and 60° (2H30, 3H30, 2H45, 3H45, 2H60 and 3H60). The total energy absorption of conventional tubes could be increased up to 46%. The effects of the case-hardened zone, quasi-static strain rate and the crush force efficiency were investigated. Moreover, the deformation modes of these case-hardened tubes were analyzed. The effect of the case-hardened forms could be classified into three categories by the gain percentage (low, intermediate and high gains). Especially in the high gain category, the material behavior seems to be directed by complicated local strain induced by the metal like-composite tube, where a triaxial strain state was encouraged particularly within the tube wall of 3H30. For this reason, the collapse load became the function of case-hardened forms. [ABSTRACT FROM AUTHOR]

This paper presents a method to optimize the dimensions of z-stiffened panels under a compressive load. Buckling coefficient curves for local buckling and stiffener lateral buckling are developed. The effects of transverse shear, coupling of buckling modes, and stiffeners on one side of the skin are considered in the column buckling stress estimation. An optimization tool is developed using MS-Excel. Examples of the design charts are presented and a design guideline is derived. [ABSTRACT FROM AUTHOR]

Abstract: Investigation of elasto-plastic stability of reticulated shells has gradually become more and more attractive to researchers. However, the analysis of the elasto-plastic stability is much more complicated than the elastic analysis, because of the involvement of both the geometrical nonlinearity and the material nonlinearity and the interactions of the two. Taking into consideration of material nonlinearity, the elasto-plastic stability behaviour of reticulated shells will be significantly different, which can only be revealed by large amount of geometrically and material nonlinear analysis of the structures. The elasto-plastic stability of seven types of commonly used single-layer reticulated shells (Kiewitt-8, Kiewitt-6, Geodesic, Schwedler Bidirectional, Schwedler Monoclonal, Sunflower, and Radial Rib) was investigated systematically with ANSYS, in which more than 2000 cases of geometrically and material nonlinear analysis were conducted with different initial geometrical imperfections, geometrical, structural and load parameters. Based on the analytical results and via comparison between elastic and elasto-plastic buckling loads, the plasticity influence coefficients were summarized for each type of the reticulated domes. These coefficients can be used to predict accurately the elasto-plastic buckling load in design practice of the reticulated domes, which is an easy way for designers to evaluate stability of the reticulated shells. [Copyright &y& Elsevier]

The aim of this study was to explore easy technologies for manufacturing of integral composite structures to evaluate the manufacturing concepts. This has been done by determining the buckling and post-buckling behavior of hat-stiffened composite panels under compression loading. A shadow Moire technique was used to monitor the out-of-plane displacement of the skin panel. The experimental results of hat-stiffened panels for initial buckling and post-buckled response of the panels were compared with numerical results obtained from linear and non-linear finite element methods. It was found to be in reasonably good agreement with each other. The panels showed good post-buckling strength and total failure began with the local buckling of the hat stiffeners. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine how the change of glass laminate fibres to flax fibres will affect the stability of thin-walled angle columns. Numerical analyses were conducted by the finite element method. Short L-shaped columns with different configurations of reinforcing fibres and geometric parameters were tested. The axially compressed structureswere simply supported on both ends. The lowest two bifurcation loads and their corresponding eigenmodes were determined. Several configurations of unidirectional fibre arrangement were tested. Moreover, the influence of a flange width change by ±100% and a column length change by ±33% on the bifurcation load of the compressed structure was determined. It was found that glass laminate could be successfully replaced with a bio-laminate with flax fibres. Similar results were obtained for both materials. For the same configuration of fibre arrangement, the flax laminate showed a lower sensitivity to the change in flange width than the glass material. However, the flax laminate column showed a greater sensitivity to changes in length than the glass laminate one. In a follow-up study, selected configurations will be tested experimentally. [ABSTRACT FROM AUTHOR]

The paper is concerned with ultimate load behavior of steel-concrete composite plate girders subjected to combined action of shear and bending. An analytical method is presented to predict the interactive response of the girder. The method considers the tension field action in the plate girder web panel and shear failure of concrete slab. The method is approximate and can be applied to composite plate girders at the preliminary stages of design. Strength of composite plate girders is investigated by varying the moment/shear ratio. It is shown that ultimate load capacity of composite plate girder is influenced by moment/shear ratio. The predicted results are compared with the corresponding finite-element values. [ABSTRACT FROM AUTHOR]

In the paper, the buckling phenomenon for static and dynamic loading (pulse of finite duration) of functionally graded plates subjected to uniform temperature increment is presented. The work deals with thin rectangular plates with unmovable edges, simply supported or clamped along all edges. The material properties varying smoothly across the thickness are assumed to be temperature-independent. The investigations are conducted for different values of volume fraction index and uniform temperature rise in form of rectangular pulse of finite duration. [ABSTRACT FROM AUTHOR]

To apply the Direct Strength Method (DSM) to web crippling of lipped channel sections, experiments were recently conducted under EOF and IOF loading conditions. In the research presented here, finite element models were first developed to predict the elastic buckling loads and the elasto-plastic behaviour, both of the experiments and an extended data set. New first- and second-order elasto-plastic theoretical models describing the plastic mechanism initiation of a 2D cross-sectional strip of the lipped channel sections were then developed. Subsequently these 2D cross-sectional models were transformed to full 3D models by using modelled yield line patterns as observed in the finite element simulations. Both the first- and second-order 3D models correlate well with the full section simulations. DSM equations were calibrated based on the results from the simulations, using several alternatives for the yield load as needed in the DSM: a first yield load from the finite element simulations; a rigid-plastic mechanism initiation load as used by other researchers; and a first-order elasto-plastic mechanism initiation load via the above theoretical models. Finally, these calibrated DSM equations were compared with the theoretical models, design codes, and a basic Merchant-Rankine approach. For the DSM, the first order rigid-plastic yield load, most appropriate for the DSM and used by other researchers also, performs best for IOF load cases. For EOF load cases, however, using the first-order elasto-plastic load in the DSM gives best results. Taking these different yield loads for the different cases then, the DSM outperforms Eurocode, AISI S100, and the basic Merchant Rankine predictions. The DSM is intuitively and relatively easy to use, and this paper shows that widening its scope to web crippling of lipped channel sections is possible. Importantly, this paper steps into the discussion for a certain type of yield load to be used in the DSM for web crippling, and gives several arguments to consider the rigid-plastic mechanism initiation load. [ABSTRACT FROM AUTHOR]

The collapse of the Interstate 35W bridge in Minneapolis, Minnesota, in 2007 brought into question the strength of large-size gusset plates in steel truss bridges. To provide new data on the behavior and strength of large-size bridge-type gusset plates, experimental tests were performed and are described in this paper. The research program focused on sway-buckling behavior and test variables included plate thickness, compression diagonal flexural stiffness, initial out-of-plane imperfection, and member load combinations. Unique to this test program was the direct consideration of different compression diagonal out-of-plane flexural stiffnesses on plate buckling behavior and capacity. Results showed that sway-buckling behavior and ultimate capacity were affected by initial out-of-plane imperfections of the plate and the out-of-plane bending stiffness of the truss compression diagonal. Results also showed that the effective length factor, , a parameter used in present load rating guides, did not accurately predict sway-buckling capacity, and the Whitmore section approach may not be the best approximation for use in plate sway-buckling behavior. A stepped-column approach was shown to illustrate and predict the effect of the plate-member stiffness interaction on buckling capacity. [ABSTRACT FROM AUTHOR]

Cylindrical shells are widely used in many kinds of applications under different cases of load combination. Nevertheless, only a small number of researches have been executed on cylindrical shells under pure bending in combination with external pressure. The present experimental research studies the buckling behavior of long cylindrical steel shells under combined pure bending and peripheral pressure. This study shows that initial sectional deformation developed by preloading considerably affects the buckling capacity of such shells. Moreover, it was found that primary load appreciably expedites the initiation of the buckling by activating the possible geometrical imperfections once shells are exposed to secondary load. [ABSTRACT FROM AUTHOR]

The conventional approach to analysis the buckling of rectangular laminates containing an embedded delamination subjected to the in-plane loading is to simplify the laminate as a beam-plate from which the predicted buckling load decreases as the length of the laminate increases. Two-dimensional analyses are employed in this paper by extending the one-dimensional model to take into consideration of the influence of the delamination width on the buckling performance of the laminates. The laminate is simply supported containing a through width delamination. A new parameter β defined as the ratio of delamination length to delamination width is introduced with an emphasis on the influence of the delamination size. It is found that (i) when the ratio β is greater than one snap-through buckling prevails, the buckling load is determined by the delamination size and depth only; (ii) as the ratio β continues to increase, the buckling load will approach to a constant value. Solutions are verified with the well established results and are found in good agreement with the latter. [ABSTRACT FROM AUTHOR]

This article presents the exact elastic buckling of annular plates with elastically restrained edges against rotation and translation at inner and outer periphery. The classical plate theory is used to derive the governing differential equation for annular plate with elastically restrained edge support system. The buckling mode may not be axisymmetric as previously assumed. In certain cases, an asymmetric mode would yield a lower (critical) buckling load. This is due to switching of mode. This work presents the critical buckling load parameters for axisymmetric and asymmetric buckling modes. Extensive data is tabulated so that pertinent conclusions can be arrived at on the influence of rotational and translational restraints, Poisson's ratio and other boundary conditions on the buckling of uniform isotropic annular plates. The numerical results obtained are in good agreement with the previously published data. In this article, the characteristic equations are exact; therefore, the results can be calculated to any accuracy. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Though thin walled steel members will locally buckle at low shear loads, they may exhibit substantial post-buckling capacity. The current cold-formed steel design code, however, does not recognize the potential post-buckling shear strength of webs, though post-buckling shear strength of stiffened webs is considered in structural plate girder design. The objective of this study is to quantify the post-buckling shear strength of slender un-stiffened webs. The finite element method based numerical investigation considered the behavior of un-stiffened simply- supported rectangular steel plates subjected to in-plane shear loadings experiencing buckling, post-buckling, and yielding until failure. The model employed representative material model, initial geometric imperfections and large deflection analysis. The investigation established the ultimate shear strength of such plates having different parametric dimensions, and compared such results with the strength values based on the current cold-formed steel design code provisions. For slender plates, the current code uses the shear buckling load as the design strength, whereas the analyses indicated significant post-buckling strength. This paper establishes the shear design equations incorporating the post-buckling capacity of un-stiffened steel plates. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents the theoretical developments of an exact finite strip for the buckling and initial post-buckling analyses of channel section struts. The presented method provides an efficient and extremely accurate buckling solution. The Von-Karman’s equilibrium equation is solved exactly to obtain the buckling loads and mode shapes for the channel section struts. The investigation of buckling behavior is then extended to an initial post-buckling study with the assumption that the deflected form immediately after the buckling is the same as that obtained for the buckling. Through the solution of the Von-Karman’s compatibility equation, the in-plane displacement functions which are themselves related to the Airy stress function are developed in terms of the unknown coefficient in the assumed out-of-plane deflection function. All the displacement functions are then substituted in the total strain energy expressions. The theorem of minimum total potential energy is subsequently applied to solve for the unknown coefficient. The developed method is subsequently applied to analyze the initial post-buckling behavior of some representative channel sections for which the results were also obtained through the application of a semi-energy finite strip method. Through the comparison of the results and the appropriate discussion, the knowledge of the level of capability of the developed method is significantly promoted. [Copyright &y& Elsevier]

Abstract: In previous studies, a proliferation of research work has been undertaken on the buckling behavior of shell structures particularly conical shells. Nonetheless, no experimental studies are found in the literature on the buckling of a full and real configured model of a slender shell reducer with two cylindrical end boundaries. To this end, buckling behavior of three conical shell reducers under uniform peripheral pressure was investigated and evaluated experimentally in this paper. In addition, relevant FE simulations as well as theoretical predictions were taken into account to compare buckling load and modes of deformation. Derived results were aimed at generalizing the data for conical reducers in full scale within the range of this study. [Copyright &y& Elsevier]

This paper investigates the buckling loads and mode shapes of the graphene sheets with two widely used boundary conditions including cantilever and doubly fixed. We employ molecular mechanics to simulate the bond between carbon atoms. Afterwards, the buckling phenomena of the graphene sheets with different dimensions and boundary conditions are studied using molecular mechanics-based finite element method. The results propose higher load values for the doubly fixed boundary condition in comparison with the other one. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this paper is to study the interaction curves along with buckling and postbuckling responses of a quasi-isotropic laminate with a centrally placed circular cutout of various sizes under uni-axial compression combined with in-plane shear loads (positive and negative). The present study is carried out using finite element method. The finite element formulation is based on the first order shear deformation theory and von Karman’s assumptions to incorporate geometric nonlinearity. The resulting nonlinear algebraic equations are solved by Newton–Raphson method. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. It is observed that pure compression- buckling, -first-ply failure and -ultimate failure strengths of the quasi-isotropic laminate with and without circular cutout decreases with increasing accompanying shear load. In addition, it is also noted that for a given uni-axial compression load, a quasi-isotropic laminate with and without a cutout can sustain higher negative shear load in comparison to the positive shear load. [Copyright &y& Elsevier]

Thin webs of glass-fiber-reinforced polymer (GFRP) girders are sensitive to shear buckling, which can be considered an in-plane biaxial compression-tension buckling problem, according to the rotated stress field theory. An extensive experimental study was performed, which shows that an increasing transverse tension load significantly increases the buckling and ultimate loads caused by a decrease in the initial imperfections and additional stabilizing effects. The stacking sequence also greatly influenced the buckling behavior. Higher bending stiffness in the compression direction increased the buckling and ultimate loads, while higher bending stiffness in the tension direction changed the buckling mode shape. The general solution obtained using the Fok model accurately modeled the experimental results, while the simplified solution (modified Southwell method) provided accurate results only at higher tension loads. [ABSTRACT FROM AUTHOR]

In this study, out-of-plane stability analysis of tapered cross-sectioned thin curved beams under uniformly distributed radial loading is performed by using the finite-element method. Solutions referred to as Bolotin's approach are analysed for dynamic stability, and the first unstable regions are examined. Out-of-plane vibration and out-of-plane buckling analyses are also studied. In addition, the results obtained in this study are compared with the published results of other researchers for the fundamental frequency and critical lateral buckling load. The effects of subtended angle, variations of cross-section, and dynamic load parameter on the stability regions are shown in graphics [ABSTRACT FROM AUTHOR]

Abstract: The aim of present investigation is to study the buckling and postbuckling response and strengths under positive and negative in-plane shear loads of simply-supported composite laminate with various shaped cutouts (i.e., circular, square, diamond, elliptical-vertical and elliptical-horizontal) of various sizes using finite-element method. The FEM formulation is based on the first order shear deformation theory which incorporates geometric nonlinearity using von Karman’s assumptions. The 3-D Tsai-Hill criterion is used to predict the failure of a lamina while the onset of delamination is predicted by the interlaminar failure criterion. The effect of cutout shape, size and direction of shear load on buckling and postbuckling responses, failure loads and failure characteristics of quasi-isotropic [i.e., (+45/−45/0/90)2s] laminate has been discussed. In addition, the effect of composite lay-up [i.e., (+45/−45/0/90)2s, (45/−45)4s and (0/90)4s] has also been reported. It is observed that the cutout shape has considerable effect on the buckling and postbucking behaviour of the quasi-isotropic laminate with large size cutout. It is also observed that the direction of shear load and composite lay-up have substantial influence on strength and failure characteristics of the laminate. [Copyright &y& Elsevier]

The paper outlines the fundamentals of the method of solving static problems of geometrically nonlinear deformation, buckling, and postbuckling behavior of thin thermoelastic inhomogeneous shells with complex-shaped midsurface, geometrical features throughout the thickness, or multilayer structure under complex thermomechanical loading. The method is based on the geometrically nonlinear equations of three-dimensional thermoelasticity and the moment finite-element scheme. The method is justified numerically. Results of practical importance are obtained in analyzing poorely studied classes of inhomogeneous shells. These results provide an insight into the nonlinear deformation and buckling of shells under various combinations of thermomechanical loads. [ABSTRACT FROM AUTHOR]

Abstract: We discuss the non-linear theory of thin shells expressed in terms of displacements of the shell reference surface as the only independent field variables. The formulation is based on the principle of virtual work postulated for the reference surface. In our approach: (1) the vector equilibrium equations are represented through components in the deformed contravariant surface base, and using the compatibility conditions the resulting tangential equilibrium equations are additionally simplified, (2) at the shell boundary the new scalar function of displacement derivatives is defined and new sets of four work-conjugate static and geometric boundary conditions are derived, as well as (3) for prescribed shell geometry all non-linear shell relations are generated automatically by two packages set up in Mathematica. The displacement boundary value problem and the associated homogeneous shell buckling problem are generated exactly without using any additional approximations following from errors of the constitutive equations. Both problems are extremely complex and available only in the computer memory. Such an approach allows us to account also for those a few supposedly small terms which may be critical for finding the correct buckling load of shells sensitive to imperfections. This approach is used in the accompanying paper by Opoka and Pietraszkiewicz [Opoka, S., Pietraszkiewicz, W., 2009. On refined analysis of bifurcation buckling for the axially compressed circular cylinder. International Journal of Solids and Structures, 46, 3111–3123.] to perform the refined numerical analysis of bifurcation buckling for the axially compressed circular cylinder. [Copyright &y& Elsevier]

The mixed degenerate shell finite element DDSE, incorporating drilling degrees of freedom, is dedicated to solve some engineering applications directly and without any numerical tricks. This finite element has shown good performances in the linear and nonlinear, isotropic and anisotropic, static problems. Thanks to the application of shear and membrane substituted strain fields; it is also free from any locking. The very satisfactory results obtained by its previous application to the nonlinear dynamic regime have suggested the present work. The formulation of the problem, the derivation of the time integration scheme and the mass matrix were conducted in the most appropriate way to deal with the dynamic buckling load prediction. Both geometrical and material nonlinearities are considered in this study. The general stability criterion of Budiansky-Ruth is used, together with the phase plane control to detect the critical dynamic buckling load. In order to evaluate the accuracy of the element and the effect of the plasticity on the critical dynamic buckling value, two selected and documented examples of the critical dynamic buckling load determination were treated. [ABSTRACT FROM AUTHOR]

Abstract: In the present paper, we attempt a novel optimisation strategy for damage resistant composite stiffened panels based on genetic algorithms and oriented towards the satisfaction of minimum weight criteria. In order to accomplish this task, first, minimum weight solutions for panel configurations with T and I stringers, satisfying the buckling resistance constraint are examined. Some minimum weight solutions are imposed to be buckling resistant only, that is, capable to sustain a given minimum admissible buckling load, while other solutions are imposed to be buckling and damage resistant, in other words, capable to sustain a given admissible buckling load being at the same time able to resist to a given impact energy without developing significant damage. Then a-posteriori evaluation of costs is performed for the best minimum weight solutions. Such an evaluation takes, at the same time, into account the manufacturing costs, which depend on the selected manufacturing process and on the geometrical configuration, and the maintenance costs which are related to impact events and consequent repairing actions. Finally, the influence of the impact damage and buckling resistance constraints on the stiffened composite panel’s costs is critically discussed providing useful considerations oriented to a cost effective composites design. [Copyright &y& Elsevier]

The cognition of the effect of cutout on the capacity of loading bearing and the buckling behavior of the cylindrical shells is crucial in designing of structures of automobiles, airplanes and marine structures. In this article, the simulation and analyzing of steel cylindrical shells with different lengths and diameters, including elliptical cutout, under bending moment with using of the numerical finite elements method was done. Furthermore, the effect of changing of cutout dimensions and the ratio of the length to diameter on buckling behavior and post buckling of cylindrical shells are studied. Finally, the relations for finding of buckling moment of these structures were presented. [ABSTRACT FROM AUTHOR]

The article comments on the paper, entitled "Buckling Behaviour of Single Pile and Pile Bent in the Scotch Road Bridge," by Y. Khodair and S. Hassiotis. The estimation of critical buckling load of embedded piles in soil was analyzed adequately by the authors. Several issues concerning the numerical modeling of pile buckling were not addressed adequately in the paper and which can be misleading.

Abstract In this paper elastic and inelastic buckling analysis of the bolted double shear lap connections (DSL) are investigated, which are commonly used in concentrically braced steel frames comprised of cold-formed hollow structural section (HSS), as brace members. By the lack of any approach to evaluate the compression strength of a DSL connections, their design is usually relied on the tension load demand developed in the brace member. The results of quasi-static cyclic tests performed on six full-scaledX-bracing specimens have shown that the discontinuous brace member with DSL connection, not designed for compression, failed and fractured by the buckling at the connection. In all the specimens, the typical brace buckling only occurred in the continuous members, as expected. In this study. a simplified elastic stability analysis is employed to calculate elastic buckling load and effective length factor usable for the design of DSL connections. Anon-linear static analysis is also performed on a suggested numerical model comprised of beam-column elements to predict the response of the studied X-bracings, exhibiting the connection and member buckling. It is shown that the results of the both suggested design procedure based on the stability analysis and the numerical model agree well with the buckling load of the test specimens. It is also indicated that the slip of connection plates decreases the compression capacity and should be considered in the analysis and design procedures. Highlights • A procedure for the design of bolted double-shear-lap connection under compression load was presented. • The anti-symmetrical buckling mode is the governing compression behavior of the X-bracingmid-connection of type DSL. • For the corner connections, the three-hinge buckling strength can be evaluated through the presented design procedure. • DSL connection compression strength decreases when slip occurred between the plate. [ABSTRACT FROM AUTHOR]

In this paper, the geometric nonlinear bending response of channel-section beams of finite length is investigated by using energy methods. The basic assumptions used in the present study are that the total strain energy of a channel-section beam subjected to pure bending can be simplified into a two-stage analysis process. One is the local bending response of the web behaving as the plate; the other is the overall bending response as a beam with flattened section. Analytical solutions for both static and dynamic instabilities of channel section beams of finite length subjected to pure bending about its minor axis are derived by applying the minimum potential energy principle. To validate the analytical solution developed, geometric nonlinear finite element analyses are also conducted. Good agreement between the present solution and the FEA results is demonstrated. The effect of beam's length on the critical load is also discussed. [ABSTRACT FROM AUTHOR]

In the construction of single layer domes and vaulted structures manufactured ball-node type connections are widely used. These ball-nodes deform due to the action of a three-dimensional state of stress while offering their resistance. These deformations result in a loss of connection stiffness, which influences the overall stability of these domes, and is usually ignored in the analysis. This work presents an investigation on the effect of ball-node deformations in the inelastic post-buckling behavior of domes and vaulted structures. A model for the load-deformation properties of the ball-nodes has been proposed in this study, in the lines of EC3-8. This connection flexibility model is integrated into a corotated–updated Lagrangian finite element formulation. Results for single layer domes and a braced barrel vault are presented. Although the present investigation deals with ball nodes only, the computational framework is still relevant for other type of connections of space structures, with modifications. [ABSTRACT FROM AUTHOR]

Abstract: It is now widely known that the presence of geometric imperfections in shell structures constitutes an important contribution to the discrepancy between theoretical and experimentally realizable ultimate loads governed by buckling. The present paper describes a method by which an actual initial imperfection field may be estimated using the service load response of a shell structure. The approach requires solving a stochastic inverse problem wherein uncertainty regarding initial imperfection predictions is expressed within the context of a Bayesian posterior distribution. The proposed approach could be applied to condition assessment and performance evaluation activities in practice. [Copyright &y& Elsevier]

As part of the Network of Excellence on Marine Structures (MARSTRUCT), a series of studies has been carried out into the buckling of glass-fibre-reinforced polymer plates with in-plane compression loading. The studies have included fabrication and testing of square, laminated panels with various thicknesses and initial geometrical imperfections, material testing, advanced finite element modelling studies and finally parametric studies covering a range of slendernesses and imperfection amplitudes. The paper provides an overview of the studies, which involved several participants in the Network. [ABSTRACT FROM AUTHOR]

Corrugated shells of revolution that may be considered cylindrical when the corrugation amplitude is small are analyzed for stability. The corrugations are transverse to the axis of revolution. Isotropic and orthotropic shells with sine-shaped meridian under uniform external compression are analyzed for stability. It is shown that the stability of corrugated shells can be significantly improved, compared with cylindrical shells, by selecting appropriate number and amplitude of half-waves. A relationship between the buckling modes and the change in the critical loads is established [ABSTRACT FROM AUTHOR]

This paper is a discussion of “Optimization for buckling loads of grid stiffened composite panels”. That paper presented an improved smear method to study the buckling behavior of stiffened composite cylindrical shells. Although this is a simple and efficient procedure but there is a basic error in superimposing the stiffness matrices of the shell and the stiffeners and calculating the equivalent stiffness parameters. This error is shown by two simple examples. [ABSTRACT FROM AUTHOR]

A slender, straight beam resting on a flat, rigid foundation does not buckle when subjected to a compressive load, since the load cannot overcome the effect of the beam's weight. However, it buckles if its ends are moved toward each other. Post-buckling of such a beam is examined, both theoretically and experimentally, for horizontal and inclined foundations. The beam is modeled as an elastica, and equilibrium states with large deflections are computed, including cases in which self-contact occurs. Frequencies and mode shapes for small vibrations about equilibrium are also determined. Agreement between the theoretical and experimental results is very good. [ABSTRACT FROM AUTHOR]

Several studies on the postbuckling behavior of compound columns subjected to different independent compressive loads are available in literature. The postbuckling problem is popularly known as the 'Elastica' problem. The compound columns contain two segments of equal length. The segments are made of two different materials with different Young's moduli with constant area moment of inertia. Alternately, this configuration can also be treated as a stepped column with constant Young's modulus, having different area moments of inertia of the segments and having the same Young's modulus. The postbuckling behavior of these compound cantilever columns, for a specific compressive load, is represented as the ratio of axial load carrying capacity, for a given free end angle in the postbuckling region to the buckling load. This problem is usually solved using either complex continuum or numerical methods. This paper contains a method of evaluation of the postbuckling behavior of the said columns through a numerical experiment that gives reliable results of the postbuckling behavior. However, the accuracy decreases, which is tolerable, as the free end rotation increases, with the limiting value of 80 degrees. [ABSTRACT FROM AUTHOR]

Curved structures, such as beams, arches, and panels are capable of exhibiting snap-through buckling behavior when loaded laterally, that is they can exhibit multiple stable equilibria, sometimes after any external loading is removed. This is a consequence of highly nonlinear force-deflection relations with perhaps multiple crossings of the zero-force axis for typical equilibrium paths. However, the propensity to maintain a stable snapped-through equilibrium position (in addition to the nominally unloaded equilibrium configuration) after the load is removed depends on certain geometric properties. A number of clamped arches are used to illustrate the relation between geometry (essentially the shape) and corresponding equilibrium configuration(s), and especially those conditions for which the initial equilibrium configuration is the only stable shape possible. Furthermore, related results are obtained when a change in the thermal environment may cause a system to exhibit a stable snapped-through equilibrium even when the system at ambient thermal conditions does not. Some representative examples are produced using a 3D printer for verification purposes. [ABSTRACT FROM AUTHOR]