Buckling analysis of skew laminate plates subjected to uniaxial inplane loads

Elastic stability of skew composite laminate plates subjected to uniaxial inplane compressive forces has been studied. The critical buckling loads of the skew laminate plates are carried out by the bifurication buckling analysis implemented in finite element program ABAQUS. The effects of skew angles, laminate layups, plate aspect ratios, plate thicknesses, central circular cutouts, and edge conditions on the buckling resistance of skew composite laminate plates are presented.     

Buckling strength of the cylindrical shell and tank subjected to axially compressive loads

This paper aims to develop practical design equations and charts estimating the buckling strength of the cylindrical shell and tank subjected to axially compressive loads. Both geometrically perfect and imperfect shells and tanks are studied. Numerical analysis is used to evaluate buckling strength. The modeling method, appropriate element type and necessary number of elements to use in numerical analysis are recommended. According to the results of the parametric study of the perfect shell, the buckling strength decreases significantly as the diameter-to-thickness ratio increases, while it decreases slightly as the height-to-diameter ratio increases. These results are different from those in the case of columns. The buckling strength of the perfect tank placed on an extremely soft foundation and a stiff foundation increases by up to 1.6% and 5.6%, respectively, compared with that of the perfect shell. The buckling strength of the shell and tank decreases significantly as the amplitude of initial geometric imperfection increases. Convenient and sufficiently accurate design equations and charts used for estimating buckling strength are provided.     

Stability analysis of stiffened plates by finite strips

The stability analysis of stiffened plates by means of the finite strip method is presented. The studies are based on the thin shallow theory, giving nonlinear strain displacement relations, but linear curvature displacement relations. The nonlinear equilibrium equations are obtained by the principle of incremental virtual work, using finite strip discretization. The higher order strip with one internal nodal line is applied. It is shown that considerable improvements can be obtained using this kind of strip. It is especially true for the postbuckling analysis. Numerical examples of the strength of stiffened plates in compression are carried out, covering a range of plate and stiffener slenderness.     

Response of stiffened and unstiffened plates subjected to blast loading

This paper describes the results of dynamic analyses carried out on both stiffened and unstiffened panels using both simplified and advanced analytical techniques. For unstiffened panels with inplane restraint along their edges, the dynamic response of an imperfect panel was predicted using a large displacement elastic analysis based on Lagrange's equation, with the panel being treated as a shallow shell. For stiffened panels, the finite element (FE) technique was used to establish the validity of using the simplified technique to predict the inter-stiffener panel displacements for a simply supported panel. A parametric study has been carried out to analyse the effects of in-plane boundary conditions, local stiffener buckling and initial imperfections on the overall response. The significant effect of boundary conditions is demonstrated by including the actual boundary conditions of a test frame in the finite element modelling of a large-scale stiffened floorplate panel used in an experimental test series.     

Buckling of steel shells subjected to non-uniform axial and pressure loading

The paper presents theoretical and numerical studies of the buckling of steel shells subjected simultaneously to axial and pressure loading. The type of combined non-uniform loading used for this analysis (horizontal pressure and wall frictional pressure which occurs in the silos) is given in the Eurocode 1 part 4. An Abaqus program was used to study the influence of the parameters affecting the strength of the shell. The results of this parametric study were used to develop a new semi-analytical method for the prediction of the critical stress of the stiffened and isotropic shells. The corresponding formulae are compared, in different examples of geometrical shells, with the results obtained by finite element simulation and by the formulae for buckling design given in recommendation EC3.     

Buckling of centerline-stiffened plates subjected to uniaxial eccentric compression

A solution for the elastic buckling of flat rectangular plates with centerline boundary conditions subjected to non-uniform in-plane axial compression is presented. The loaded edges are simply supported, the non-loaded edges are free, and the centerline is simply supported with a variable rotational stiffness. The Galerkin method is used to establish an eigenvalue problem and a series solution for plate buckling coefficients is obtained by using combined trigonometric and polynomial functions that satisfy the boundary conditions. It is demonstrated that the formulation approaches the classical solution of a plate with a clamped edge as the variable rotational stiffness is increased. The variation of buckling coefficient with aspect ratio is presented for various stress gradient ratios. The coupling between plate aspect ratio, centerline rotational stiffness, and gradient of applied compressive stress is illustrated and discussed. The solution is applicable to stiffened plates and I-shaped beams that are subjected to biaxial bending or combined flexure and torsion, and is important to estimate the reduction in elastic buckling capacity due to stress gradient.     

Nonlinear finite element analysis of CFT-to-bracing connections subjected to axial compressive forces

The Abaqus finite element program together with nonlinear material constitutive models for concrete-filled tube (CFT) and steel gusset plate is used to analyze the behaviors of the gusset plate type CFT-to-Bracing connections subjected to axial compressive forces. It is found that the failure of CFT-to-Bracing connections occurs below the connecting area. Local bulged shapes of the steel tube might take place in the areas close to the gusset plate and the fixed end under the failure stage. The ultimate strengths of the CFT columns slightly increase with the increasing of the load ratio and the thickness of the gusset plate. The introduction of the cutouts on the gusset plates slightly increases the ultimate strength of the CFT column and causes more local bulged shapes on the steel tubes below the connection area under the failure stage.     

带肋方钢管混凝土柱偏心受压力学性能研究

在方钢管混凝土管壁内设置纵向加劲肋可提高其管壁的稳定性。采用有限元软件ABAQUS对带肋方钢管混凝土柱偏心受压荷载-变形全过程关系进行计算,计算得到的破坏形态和荷载-变形关系曲线与试验结果符合较好。在此基础上,通过典型算例从变形情况、荷载-变形全过程曲线、核心混凝土的纵向应力分布以及钢管与混凝土相互作用四个方面对带肋方钢管混凝土的工作机理进行分析,并且与相应的无肋方钢管混凝土进行对比。研究结果表明:加劲肋的设置可以增加钢管约束支撑点,减小鼓曲的横向变形值,增强核心混凝土与管壁之间的相互作用,进而有效地延缓构件局部屈曲,改善管壁的稳定性,提高构件的极限荷载;纵向加劲肋宽度越大,构件极限荷载越高,后期延性越好;加劲肋宽度设置应控制在一定范围,能获得较好的综合经济效果。     

Collapse behavior of thin rectangular plates subjected to partial biaxial compression

The post-buckling behavior and the ultimate strength of simply-supported, thin, rectangular, steel plates subjected to partial biaxial compressive loads have been established in this study. The computer-aided analytical technique used accounts for large deflections, elastic-perfectly plastic material behavior, residual stresses and initial out-of-plane deflections. The method of analysis is based on the principle of minimum potential energy and the Rayleigh-Ritz solution procedure. However, the solution procedure has been applied in an incremental step-by-step manner. The influences of initial imperfections such as out-of-plane deflections and residual stresses, and the plate width-to-thickness ratio on the behavior and the ultimate strength of such plates have been discussed in detail. The results of the parametric study are presented in graphical form and summarized by simple design curves.     

Buckling of circular plates under intermediate and edge radial loads

This brief note is concerned with the elastic buckling problem of a circular plate subjected to both intermediate and edge radial loads. The stability criteria, in the form of transcendental equations, are derived as a function of the location of the intermediate load and the ratio of the magnitudes of the intermediate load and the edge load. Sample buckling results are presented for this new buckling problem.     

Buckling of laminated composite stiffened panels subjected to in-plane shear: A parametric study

The presence of in-plane loading may cause buckling of stiffened panels. An accurate knowledge of critical buckling load and mode shapes are essential for reliable and lightweight structural design. This paper presents some parametric studies on simply supported laminated composite blade-stiffened panels subjected to in-plane shear loading. A total of 450 models were analyzed using ANSYS 7.1 and a database is prepared for different plate and stiffener combinations. 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 extensional stiffness to shear stiffness ratio of the plate. Based on the studies, few important parameters influencing the buckling behaviour are identified and guidelines for better stiffener proportioning are developed, which will be helpful for the designer.     

Strength assessment of steel plates subjected to compressive load and dent deformation

This work presents an assessment of the ultimate compressive strength of damaged steel plates with a local dent. Extensive non-linear finite element analyses are performed, where three groups of analyses are considered. In the first group, the effect of the dent orientation (longitudinal and transverse) is studied for three plate thicknesses. For the second group, the direction of the dent depth (upward and downward) with respect to the global initial imperfection is explored. In the third group, the variation of the dent size for several plate thicknesses and its influence on ultimate compressive strength is investigated. The post-collapse behaviours are discussed and the inflection plate slenderness with and without dent is observed, at which the behaviour of the plate changed. A certain dent breadth to the plate breadth ratio is established, revealing the different plate response. Based on the performed analyses, a generalised expression of the ultimate strength reduction factor due to dent is developed.     

Buckling analysis of cracked plates using hierarchical trigonometric functions

The present paper deals with the estimation of buckling loads of plates with cracking damages. The hierarchical trigonometric functions are used to define the displacement function of the cracked plate. Selective choosing of the trigonometric functions satisfies the various boundary conditions of a plate bounded by support members in a continuous plated structure. Moreover, the analysis of the cracked plate can be carried out with a minimum number of equations accurately. In the present paper, the buckling loads of plates with various types of cracks, such as edge crack and central crack, are estimated under uniaxial compressive load, biaxial compressive load and in-plane shear load. The results are found to correlate well with those obtained using a finite element method.     

Buckling of vibrations of shear-flexible orthotropic plates subjected to mixed boundary conditions

An approximate technique is presented for the analysis of buckling and vibrations of free-form, orthotropic, shear-flexible (‘Mindlin’) plates subject to mixed boundary conditions. The method falls into the category of Rayleigh/ Ritz-techniques; however, by using Lagrangian multipliers to ‘relax’ the geometric boundary conditions, the selection of appropriate trial functions is made considerably simpler. Accuracy and reliability of the proposed technique is demonstrated on the basisof several sample problems.     

Buckling analysis of stiffened circular cylindrical panels using differential quadrature element method

Differential quadrature element method (DQEM) for buckling analysis of stiffened circular cylindrical panels subjected to axial uniform compressive stresses is presented for the first time. The methodology and procedures are worked out in detail. The circular cylindrical panel and the stiffeners are treated separately. Governing differential equations are derived based on the equilibrium of the panel and the stiffener, and on compatibility conditions along the interface of panel elements and stiffeners. Torsional stiffness of the stiffener is ignored. Circular cylindrical panels with a stringer stiffener or a chordwise stiffener are analyzed by the DQEM, and the results are compared with previously published data to verify the established methodology and procedures. Some new results are presented for the circular cylindrical panels with two orthogonal stiffeners.     

Buckling and postbuckling of unsymmetrically laminated angle-ply plates in uniaxial and biaxial compression

A deflection-type perturbation technique is proposed to solve the nonlinear Karman equations of rectangular unsymmetrically laminated angle-ply composite plates with simply supported edges in uniaxial and biaxial compression. Higher-order asymptotic expansions for postbuckling behavior of the plates are constructed by this approach. Effects of initial imperfection, lamination angle and number of layers on buckling and postbuckling of the plates are examined. In some specific cases numerical results obtained from the present solution are in fairly good agreement with other theoretical predictions.     

Buckling and dynamic instability analysis of stiffened shell panels

The static and dynamic instability characteristics of stiffened shell panels subjected to uniform in-plane harmonic edge loading are investigated in this paper. The eight-noded isoparametric degenerated shell element and a compatible three-noded curved beam element are used to model the shell panels and the stiffeners, respectively. As the usual formulation of degenerated beam element is found to overestimate the torsional rigidity, an attempt has been made to reformulate it in an efficient manner. Moreover, the new formulation for the beam element requires five degrees of freedom per node as that of shell element. The method of Hill's infinite determinant is applied to analyze the dynamic instability regions. Numerical results are presented through convergence and comparison with the published results from the literature. The effect of various parameters like shell geometry, stiffening scheme, static and dynamic load factors, stiffener size and position, and boundary conditions are considered in buckling and dynamic instability analysis of stiffened panels subjected to uniform in-plane harmonic loads along the boundaries.     

Stability criteria for rectangular plates subjected to intermediate and end inplane loads

This paper is concerned with the elastic buckling of rectangular plates subjected to intermediate and end uniaxial inplane loads, whose direction is parallel to two simply supported edges. The aforementioned buckling problem is solved by decomposing the plate into two subplates at the location where the intermediate uniaxial load acts. Each subplate buckling problem is solved exactly using the Levy approach and the two solutions brought together by matching the continuity equations at the separated interface. It is worth noting that there are five possible solutions for each subplate and consequently there are 25 combinations of solutions to be considered. For different boundary conditions, the buckling solutions comprise of different combinations. For each boundary condition, the correct solution combination depends on the ratio of the intermediate load to the end load. The exact stability criteria, presented both in tabulated and in graphical forms, should be useful for engineers designing walls or plates that have to support intermediate floors/loads.     

Simple and combination resonances of rectangular plates subjected to non-uniform edge loading with damping

The effects of damping on the behaviour of simple and combination resonances of simply-supported rectangular plates subjected to non-uniform in-plane periodic loading are studied. Finite element formulation is applied to obtain the equilibrium equation for the plate. The relations for the boundaries of parametric instability regions are obtained by using the method of multiple scales. The results show that under localized edge loading, combination resonance zones are as important as simple resonance zones. For nearly uniform loading, the combination resonance zones are very small in width and may disappear in the presence of slight damping. The effects of damping show that there is a finite critical value of the dynamic load factor for each zone below which the plate cannot become dynamically unstable. It is also shown that the effects of damping on the combination resonances may be destabilizing under certain conditions.