Local Plate Buckling Research Articles

Local buckling of moderately thick stepped skew viscoelastic composite plates using the element-free Galerkin method

In this paper, the quasi-static stability of moderately thick skew viscoelastic composite plates subjected to in-plan forces is analyzed using the element-free Galerkin method. The study is based on the first-order shear deformation theory and the method of effective moduli. The shape functions are constructed using the moving least squares approximation and the essential boundary conditions are introduced into the formulation through the Lagrange multiplier method and the orthogonal transformation techniques. The method is programmed and several numerical examples are presented to demonstrate the scope and efficacy of the procedure. Also, local buckling of viscoelastic stepped plates is studied.

Effective width method to account for the local buckling of steel thin plates at elevated temperatures

The local buckling of thin steel plates exposed to fire is investigated using a finite element model. The reduction of strength and stiffness that occurs at elevated temperatures needs to be taken into account in the design, as it increases the susceptibility to local buckling of the plates thus affecting their load carrying capacity. The obtained results show that the current existing design method of Eurocode 3 to take into consideration the local buckling in the calculation of the ultimate strength of steel thin plates at elevated temperatures needs to be improved. These methods are based on the same principles as for normal temperature but using for the design yield strength of steel, at elevated temperatures, the 0.2% proof strength of the steel instead of its strength at 2% total strain as for the cases where the local buckling is not limiting the ultimate strength of the plates. This consideration, however, leads to an inconsistency if cross-sections are composed simultaneous of plates susceptible and not to local buckling. To address this issue, new expressions for calculating the effective width of internal compressed elements (webs) and outstand elements (flanges) are proposed, which have been derived from the actual expressions of the Part 1.5 of the Eurocode 3 and validated against numerical results. It is also demonstrated that it is not necessary to use for the yield stress at elevated temperatures the 0.2% proof strength of the steel instead of the yield stress at 2% total strain, given that the necessary allowances are considered in these new expressions, thus leading to a more economic design.

Numerical analysis of static performance comparison of friction stir welded versus riveted 2024-T3 aluminum alloy stiffened panels

Most researches on the static performance of stiffened panel joined by friction stir welding(FSW) mainly focus on the compression stability rather than shear stability. To evaluate the potential of FSW as a replacement for traditional rivet fastening for stiffened panel assembly in aviation application, finite element method(FEM) is applied to compare compression and shear stability performances of FSW stiffened panels with stability performances of riveted stiffened panels. FEMs of 2024-T3 aluminum alloy FSW and riveted stiffened panels are developed and nonlinear static analysis method is applied to obtain buckling pattern, buckling load and load carrying capability of each panel model. The accuracy of each FEM of FSW stiffened panel is evaluated by stability experiment of FSW stiffened panel specimens with identical geometry and boundary condition and the accuracy of each FEM of riveted stiffened panel is evaluated by semi-empirical calculation formulas. It is found that FEMs without considering weld-induced initial imperfections notably overestimate the static strengths of FSW stiffened panels. FEM results show that, buckling patterns of both FSW and riveted compression stiffened panels represent local buckling of plate between stiffeners. The initial buckling waves of FSW stiffened panel emerge uniformly in each plate between stiffeners while those of riveted panel mainly emerge in the mid-plate. Buckling patterns of both FSW and riveted shear stiffened panels represent local buckling of plate close to the loading corner. FEM results indicate that, shear buckling of FSW stiffened panel is less sensitive to the initial imperfections than compression buckling. Load carrying capability of FSW stiffened panel is less sensitive to the initial imperfections than initial buckling. It can be concluded that buckling loads of FSW panels are a bit lower than those of riveted panels whereas carrying capabilities of FSW panels are almost equivalent to those of riveted panels with identical geometries. Finite element method for simulating static performances of FSW and riveted stiffened panels is proposed and evaluated and some beneficial conclusions are obtained, which offer useful references for analysis and application of FSW to replace rivet fastening in aviation stiffened panel assembly.

A Fully Discretized Nonlinear Finite Strip Formulation for Pre-Buckling and Buckling Analyses of Viscoelastic Plates Subjected to Time-Dependent Loading

A semi-analytical fully discretized finite strip method is developed to investigate the pre-buckling and local buckling of viscoelastic plates with different boundary conditions subjected to time-dependent loading. The mechanical properties of the material are considered to be linear viscoelastic by expressing the relaxation modulus in terms of Prony series. The fully discretized finite strip equations are developed using a two-point recurrence formulation, which leads to a computationally superior formulation. Time history of maximum deflection of plates with different end conditions is calculated. The effects of thickness, length of plate, and transverse loading on critical buckling load are also studied.

Tensile resistance of J-hook connectors used in Steel-Concrete-Steel sandwich structure

Steel-Concrete-Steel (SCS) sandwich panel with ultra-lightweight cement composite core has been proposed to produce slim decking for bridge and building construction. One special feature of this lightweight sandwich panel is the use of J-hook connectors to improve the structural performance against combined actions of vertical shear and bending moment on the section. The proposed J-hook connectors provide effective bond between the steel and concrete, prevent local buckling and separation of the steel face plate, and enhance the transverse shear resistance to the structure. This paper investigates the tensile resistance of this new form of J-hook connectors by performing tensile tests on 79 sandwich specimens with various types of core materials including normal weight concrete, lightweight concrete, and ultra-lightweight cement composite. Their ultimate tensile resistances were obtained and corresponding failure modes were reported. The main parameters that influenced the tensile resistance of J-hook connectors were discussed and analyzed. Theoretical methods were developed to predict the tensile resistance of the J-hook connectors and their accuracy was verified against test results. Finally, recommended methods were proposed for design purposes.

Local–overall interactive buckling of welded stainless steel box section compression members

The interaction between local and overall buckling of welded stainless steel columns has been investigated experimentally and numerically in this study. Eight stainless steel box section compression members were fabricated from slender hot-rolled plates. The material properties and welding residual stress patterns in the test specimens had been obtained previously. Initial geometric imperfections, both local and global, were accurately measured prior to the tests. The test specimens were axially loaded between two pin-ended supports, and both local plate buckling and overall flexural buckling featured visibly in the observed failure modes. Finite element (FE) models were also set up using the ABAQUS software package to conduct numerical simulations, which were initially validated by means of comparison with the experimental data. Using the validated FE models, parametric studies were carried out to assess the influence of the key input parameters, such as the residual stresses, the material strain hardening exponent and non-dimensional proof stress, geometric imperfections and slenderness ratios. Existing design methods, including the design provisions of Eurocode 3 Part 1.4, the design proposal of Rasmussen and Rondal, the direct strength method (DSM) for cold-formed carbon steel and two revisions thereof, were all evaluated against the obtained test and numerical results. It was revealed that the EN 1993-1-4 buckling curves, which do not differ with grade, provide reasonable average strength predictions, but tend to slightly overpredict the local–overall buckling resistances of welded austenitic stainless steel members and slightly underestimate those of duplex stainless steel members. Furthermore, the three considered DSM design curves, all of which were developed on the basis of structural performance data from cold-formed sections, provide generally unconservative strength predictions for welded stainless steel sections. Based on the generated data points, modifications to the current EN 1993-1-4 provisions and the DSM have been proposed, which offer more accurate strength predictions for local–overall interactive buckling resistances of welded stainless steel box section columns.

上フランジを連続完全拘束されたH形断面梁の弾性座屈耐力

This study aims to develop approximate formulas to calculate the elastic buckling strength of H-shaped beams with continuous complete restraint on the upper flange by theoretical analysis, and to examine the coupled effect between plate local buckling and lateral buckling under restraint. As a result, the following conclusions are reached: (1) The elastic lateral buckling strength of H-shaped beams with continuous complete restraint on the upper flange is expressed by the equation proposed in this study. (2) The effect of continuous restraint to plate local buckling strength is little. (3) Continuous restraint on the upper flange increases lateral buckling strength but the coupled effect between plate local buckling and lateral buckling under restraint can decrease buckling strength.

Study on Stability Performance of Friction Stir Welded Aluminum Alloy Stiffened Panel under Shear Load

Shear experiment on friction stir welded 2024-T3 aluminum alloy stiffened panel specimens is conducted to obtain the buckling behavior and carrying capability of the structure. Finite element method(FEM) is applied to analyze the stability performance of the simplified structure model and the results are compared with experimental results. It is found that, buckling mode of the structure is local buckling of plate between stiffeners, post-buckling mode is under the state of diagonal tension, the failure patterns mainly contain the plastic deformation and tearing of plate, distortion of stiffeners and local weld debonding. Average carrying capability of specimens failed with weld debonding is 7.7% lower than that of other specimens. Buckling loads obtained by linear and nonlinear analysis are separately 18.4% and 26.2% higher than average experimental result, while carrying capability obtained by nonlinear analysis is 5.7% higher than average experimental result, which indicates that the carrying capability is less sensitive to the weld induced initial imperfections than buckling load. Buckling mode and failure pattern obtained by FEM accords well with experimental phenomenon, which validates the rationality of the finite element model, however, it still needs to be further modified to account for weld induced imperfections to reduce the calculation errors..

Load-carrying behaviour of web-core sandwich plates in compression

This paper investigates theoretically the compressive load-carrying behaviour of geometrically imperfect web-core sandwich plates. Slender plates, which first buckle globally, are considered. The study is carried out using two approaches, both solved with the finite element method. The first is the equivalent single-layer theory approach. First-order shear deformation theory is used. The second approach is a three-dimensional shell model of a sandwich plate. Plates are loaded in the web plate direction. Simply supported and clamped boundary conditions are considered with a different level of in-plane restraint on the unloaded edge. The results show that the behaviour of the sandwich plate is qualitatively equal to the isotropic plate of the same bending stiffness for deflections lower than the plate thickness. As the deflections increase, the lower in-plane stiffness of the sandwich plate results in lower post-buckling stiffness. Local buckling of face plates in the post-buckling range of the sandwich plate further reduces the structural stiffness.

Plastic coupled instabilities of I-shaped steel beams

The paper presents the case of plastic instability of I-shaped beams where the rotation capacity is a very important characteristic in order to assure the required ductility in plastic or seismic design. The failure of such beams can be due to the local plastic plate buckling of compression flange and local plate buckling of the web in flexural compression, produced in-plane or out-of-plane. In the same time the failure can occurs by coupling of these two local buckling modes. In order to study the plastic buckling of beams and to determine the available rotation capacity which is required by the plastic or seismic design, the collapse plastic mechanism theory was developed and a specialized computer program DUCTROT-M was elaborated. The parametrical analysis reveals the paramount importance of the web to thickness ratio and furthermore the sensitivity in out-of-plane buckling of the European hot-rolled sections.

Numerical analysis of semi-elliptical hollow section columns

The buckling behaviour, ultimate strength and failure of columns with semi-elliptical hollow section are examined in this paper, using finite-strip analyses and shell finite-element analyses. Semi-elliptical hollow sections are a unique case of section shape, since they possess a flat part (plate behaviour) and a semi-elliptical part (shell behaviour). Assessing the contribution of each part to the buckling and ultimate behaviour of semi-elliptical hollow section columns is the main objective of this paper. The buckling behaviour is first analysed using finite-strip software and the ultimate behaviour is then studied using shell finite-element software. From the finite-strip results it is shown that local buckling of semi-elliptical hollow section columns is solely governed by the instability of the flat part. From shell finite-element results it is shown that the ultimate behaviour is mostly governed by the pre-buckling stiffness of the semi-elliptical part. Some columns have ultimate loads well above the critical load (associated with local plate buckling) due to the stiffness of the semi-elliptical part, for which the buckling stress is much higher than that of flat part. Finally, some preliminary design guidance is proposed. An expression to predict the ultimate strength is presented and shown to provide accurate results.

Buckling Analysis of Composite Plates in Plate-Cone Reticulated Shell

Plate-cone reticulated shell is a new type of space structures with good mechanical behavior and technical economy. In this paper, local buckling and influence factors of composite plates in plate-cone reticulated shell are analyzed with theory of composite plate and shell through composite structure finite element method, and the mechanical characteristics of composite plate-cone reticulated shell are studied, some important conclusions were obtained, which can provide theoretical foundation for practical design of composite plate-cone reticulated shell and composite plates.

Special Issue on Stability of Composite Structures

The increased use of composites in aerospace and civil engineering has resulted in growing demand for engineers versed in the advanced design of composite structures. Composite structures are understood in the wide sense, including microstructured materials, composite structural shapes, composite members built up by subelements of various materials, laminate or sandwich members, small-scale composite structures, etc. Compositelike structural elements are increasingly used in traditional engineeringfields, such as civil engineering, mechanical engineering, or aeronautical engineering, and they have also found some new applications with some recent developments, such as biomedical engineering or biomechanics, nanotechnology, etc. This special issue is primarily based on the presentations given in the symposium on the stability of composite structures organized by the EngineeringMechanics Institute (EMI) Stability Committee during the ASCE EMI Annual Conference held in Boston on June 2–4, 2011. This symposium has provided a forum to discuss recent advances and address the future prospects in the area of the stability of composite structures. The symposium has covered a large number of topics related to the stability of composite structures including the following: • Buckling of composite members; • Plate buckling; • Buckling and vibration of thin-walled structures; • Shear and large displacement analysis; • Interactive buckling and nonlocal mechanics; • Shear effects for in-plane and out-of-plane analyses; • Inelastic buckling; • Anisotropic effects, microstructured materials, and stability problems; • Buckling of sandwich structures; • Stability of partially composite members and delamination effects; • Postbuckling; and • Dynamic buckling. After going through an external review process, the following papers have been accepted and are included in this special issue on the stability of composite structures. As indicated by the title of this special issue, most of the presented papers uniquely deal with the challenges in stability analysis brought by the complexity of composite materials and structures. Their specific advances by these contributions are briefly summarized as follows: 1. In “Local Buckling Analysis of Restrained Orthotropic Plates under Generic In-Plane Loading,” Qiao et al. investigated analytically and numerically the local buckling of composite orthotropic plates under generic in-plane loading and with rotationally restrained boundary conditions. They used both semianalytical and finite-element method (FEM) numerical approaches to characterize the stability behavior of laminated plates or panels of fiber-reinforced plastic structural shapes. The approximated semianalytical solution is obtained from the variationally based Rayleigh-Ritz method, and it is successively compared with available results published in the literature. 2. In “Modeling of Interactive Buckling in Sandwich Struts with Functionally Graded Cores,” Yiatros et al. studied the interactive buckling in sandwich struts with functionally graded cores. The postbuckling behavior is analyzed for this sandwich column composed of two Euler-Bernoulli extensible columns connected with a shear functionally graded core. Linearized and nonlinear analyses are presented for this nonlinear elastic structural problem, and the possibility of capturing secondary bifurcations for such nonlinear systems is numerically shown. This nonlinear model is compared successively to some FEM results based on two-dimensional analyses for the core behavior. 3. In “Buckling Loads of Two-Layer Composite Columns with Interlayer Slip and Stochastic Material Properties,” Schnabl et al. presented an efficient stochastic buckling model for studying the structural reliability of layered composite columns with interlayer slip between the layers and random material and loading parameters. The deterministic model is composed of two connected elastic columns with the shear effect neglected for each column. The nonderterministic approach is based on the exact buckling model, response surface method, and Monte Carlo simulations. The probability of failure for this stochastic buckling problem is computed, and it is shown to be very sensitive to loading and material distribution parameters. 4. In “Effect of Fiber Orientation on Buckling and First-Ply Failures of Cylindrical Shear-Deformable Laminates,” Cagdas and Adali investigated the effect of fiber orientation on buckling and first-ply failures of cylindrical shear-deformable laminates using an 8-node shell finite element (FE). The best ply angle is optimized for each stacking sequence to maximize the failure load. They identified that the rotational restraints at the curved edges have a pronounced effect on the failure load. 5. In “Thermal Postbuckling of Shear Deformable FGM Cylindrical Shells Surrounded by an Elastic Medium,” Shen incorporated the additional effect of an elastic medium on the thermal postbuckling of shear deformable functionally graded material (FGM) cylindrical shells. The surrounding elastic medium is modeled as a Pasternak foundation. The nonlinear governing equations are solved using a singular perturbation technique. The numerical results show that in some cases the FGM cylindrical shell with an intermediate volume fraction index does not have an intermediate buckling temperature and thermal postbuckling strength. In the case of heat conduction, the nonlinear equilibrium path for geometrically perfect FGM shells with simply supported boundary conditions is no longer of the bifurcation type. 6. In “Generalized Beam Theory to Analyze the Vibration of Open-Section Thin-Walled Composite Members,” Silvestre

Development and Application of CFT without Fire Protection using High Performance Steel and Concrete

Concrete filled tube (CFT) columns, which consist of a steel tube filled with concrete, combine the benefits of the two materials. The steel tube provides a confining pressure to the concrete, while the local buckling of steel plate can be prevented by the concrete core. CFT columns also have a high fire resistance due to the heat storage effect of concrete under fire. For this reason, it is possible to develop CFT columns without fire protection measures. CFT columns without fire protection have many advantages, including quality control, cost reduction, better space efficiency and a shorter construction period. Due to these advantages, studies on the development of CFT columns without fire protection measures have been performed. However, CFT columns lose their bearing capacity under fire because the steel tube is exposed to the outside. As a result, the structure is collapsed, causing significant damage. In this research, we made a CFT column using high strength concrete (100 MPa) and high strength steel (800 MPa). We use steel fiber and nylon fiber with concrete to provide fire resistance. We perform the fresh concrete experiment and investigate the fire resistance of the CFT column (<TEX>${\Box}400{\times}400{\times}15{\times}3000mm$</TEX>) under loading. To investigate the effect of steel fiber on increasing fire resistance, we compare the fire resistance time according to the steel fiber. Through the test, it was found that the CFT specimen with steel fiber had better fire resistance performance than other cases.

Experimental investigation and design of thin-walled concrete-filled steel tubes subject to bending

A series of bending tests of thin-walled concrete-filled steel tubes (CFST) were presented in this study. A total of 4 specimens were tested, two square specimens and two rectangular specimens, with width to wall thickness ratio ranging from 50 to 100. The load–displacement curves, failure mode and ultimate capacity of test specimens were obtained. An analytical model was developed for the thin-walled CFSTs subjected to bending. Material properties of confined concrete, corner strength enhancement of cold-formed steel sections, residual stresses and plate local buckling were considered in the developed model. The proposed model was able to predict the behavior and strengths of test specimens with reasonable accuracy. In addition, the suitability of current AISC standard, Eurocode 4 and Han's model for thin-walled CFSTs subjected to bending was also evaluated.

Flexural behaviour of steel plate-masonry composite beams

Steel plate-masonry composite structure is a newly-developed type of structural technique applicable to existing masonry buildings by which the load-bearing walls can be removed for large spaces. This kind of structure has been used in practice for its several advantages, but experimental investigation on its elements is nearly unavailable in existing literature. This paper presents an experimental study on the flexural behaviour of four steel plate-masonry composite beams loaded by four-point bending. Test results indicate that failure of the tested beams always starts from the local buckling of steel plate, and that the tested beams can satisfy the requirement of service limit state. In addition, the assumption of plane section is still remained for steel plate prior to local buckling or steel yielding. By comparative analyses, it was also verified that the working performance of the beam is influenced by the cross-section of steel plate, which can be efficiently enhanced by epoxy adhesive rather than cement mortar or nothing at all. Besides, it was also found that the contribution of the encased masonry to the flexural capacity of the composite beam cannot be ignored when the beam is injected with epoxy adhesive.

Behavior of Steel–Concrete–Steel sandwich structures with lightweight cement composite and novel shear connectors

In Steel–Concrete–Steel (SCS) sandwich structure, mechanical shear connectors are commonly used to transfer longitudinal shear forces across the steel–concrete interface. In this paper, novel shear connectors such as J-hook and cable shear connectors are proposed and their performance to achieve composite strength of SCS sandwich structures is investigated. The use of these connectors together with ultra-lightweight cement composite core reduces the overall weight of SCS sandwich system making it suitable for the construction of marine and offshore structures. Static tests were carried out on SCS sandwich beams with J-hook, cable shear connectors and headed studs. Their ultimate strengths were reported and their respective failure modes were discussed. An analytical method to predict the ultimate strength of the Steel–Concrete–Steel sandwich beams with various types of shear connectors was developed and its accuracy was ascertained by comparing with the test results. Deign recommendations are made on minimum connector spacing to prevent shear cracking of concrete core and local buckling of face plates.

Global and local buckling of sandwich circular and beam-rectangular plates with metal foam core

The paper is devoted to the analytical, numerical and experimental studies of the global and local buckling–wrinkling of the face sheets of sandwich beams and sandwich circular plates. A mathematical model of displacements, which includes a shear effect, is presented. The governing differential equations of sandwich plates are derived. The equations are analytically solved and the critical loads are obtained. Finite element models of the plates are formulated and the critical loads and buckling modes are calculated. Moreover, experimental investigations are carried out for the family of sandwich beam-plates. The values of the critical load obtained by the analytical, numerical (FEM), and experimental methods are compared.

Experimental verification of an inelastic plate theory based on plastic flow theory

The paper aims to verify a recently proposed inelastic plate theory by Becque (2010) [1]. In a first part, the theory is revisited and some necessary corrections to the derivation are presented. A total of 486 data points pertaining to the local buckling of aluminium and stainless steel plates and plate assemblies were collected from literature in order to be compared to the predictions of the theory. For plates with straightforward boundary conditions (either simply supported edges or free edges), the theoretical buckling load was obtained by solving Becque's differential equation analytically or numerically. For plate assemblies with less obvious boundary conditions, including plain channels, lipped cannels, Z- and H-sections, the buckling load was obtained by employing an inelastic semi-analytical finite strip method based on Becque's differential equation. Including all data points, the average ratio of the predicted buckling load to the experimentally measured buckling load was 0.98 with a standard deviation of 0.069, thus confirming the proposed theory.

Experimental Research and Finite Element Analysis of Concrete-Filled Steel Box Columns with Longitudinal Stiffeners

For further study of mechanical properties of concrete-filled steel box columns (CFSBCs) with longitudinal stiffeners, axially loading tests of CFSBCs with longitudinal stiffeners was conducted to obtain their ultimate bearing capacity and failure modes. The test results were compared with those of hollow steel box columns with longitudinal stiffeners. Cross section of the test specimen was scaled from a chord member of Dongjiang Bridge. The experimental results show that failure mode of CFSBCs with longitudinal stiffeners is local buckling of steel plates, which is different from that of concrete-filled thin wall steel tube columns with longitudinal stiffeners. Although longitudinal stiffeners can prevent global buckling of steel plates, the effect is less obvious than that of concrete-filled thin wall steel tube columns. Meanwhile, three-dimensional finite element models (FEM) of the specimens were modeled using computer program ANSYS to obtain bearing capacities and load-strain curves. The FEM results coincide quite well with the test results. Further, influence of width to thickness ratio on mechanical behavior of CFSBCs was analyzed using FEM.