Local Plate Buckling Research Articles

Ultimate Strength Analysis of Horizontally Curved Steel Box Girders Considering Local Buckling of Web Plates and Distortion

Ultimate Strength Analysis of Horizontally Curved Steel Box Girders Considering Local Buckling of Web Plates and Distortion

Finite element simulation of slender thin-walled box columns by implementing real initial conditions

This paper deals with the numerical simulation of tests on slender thin-walled box columns, susceptible to combined instability: to global Euler buckling and to local buckling of steel plates. Eight full-scale tests were carried out with different global slenderness of welded and cold-formed columns subjected to centric and eccentric compression. Initial column geometry and residual stresses were measured and carefully implemented in numerical models. The results of FEA simulations show good agreement with the test results. On verified numerical model the influence of different initial imperfections was studied and various equivalent geometric imperfections were tested for the considered column configurations.

Beam and shell element model for advanced analysis of steel structural members

Plastic zone method of advanced analysis, which uses shell elements to model the entire structure, is the most accurate method available to predict the ultimate strength and behavior of steel frames. The disadvantage of such full shell plastic zone models is that it is computationally expensive and hence its use is limited to small structures. Beam elements in commercial finite element packages can model residual stress and capture spread of plasticity, but cannot model local buckling of plates that the member is made up of, which leads to unloading and failure in steel frames. A hybrid model using shell elements only in the regions vulnerable to elastic or inelastic local buckling and beam elements in other locations could overcome this limitation of full beam element model. The issues in using this hybrid model are, knowing a priori the location and length of the shell element region and connecting the beam and shell regions without any artificial stress concentrations or incompatible displacements. In this study, in addition to addressing these issues, the hybrid model is systematically evaluated by studying its performance in structural elements. It is seen that the hybrid model strength predictions has an average error of only 0.91% but requires on an average 83% less computational time when compared to the full shell plastic zone models.

Behaviour of Filled Rectangular Steel HSS Composite Columns under Bi-Axial Bending

The purpose of this study was to investigate the behaviour of concrete-filled rectangular steel hollow structural section (HSS) columns formed by slender plates with large depth-to-width ratio subjected to bi-axial bending. As part of this study, four large concrete-filled thin-walled rib-stiffened rectangular HSS columns have been tested. Their steel tubes possess a depth-to-width ratio of 2.38 and a depth-to-thickness ratio of 175. Rib stiffeners were welded to the plate walls such that the stiffened plate width-to-thickness ratio (= 45) was less than that specified (= 60) in the Chinese design code. The results showed that local buckling of steel plate appeared after the specimen reached the ultimate capacity. Also, the fiber element analysis method is adapted to analyze the behaviour of specimen, in which the change of neutral axis position is considered. At last, the experimental results are compared with the values calculated from design codes, namely EC4, LRFD, CECS and DBJ. The results show that all codes provide safe ultimate capacities. Among them, the capacities calculated from DBJ yield results closest to the experimental ones and the other three design codes produce safety over 20%.

Elastic local buckling of perforated webs of steel cellular beam–column elements

In this study, the finite element method is employed to determine the critical in-plane longitudinal load at which elastic local buckling of the web of cellular beam–column elements occurs. To simplify the simulation of the problem, the interaction between the flanges and perforated web is approximated by modelling the web only as a long plate having aspect ratio ( L / h w ≥ 10 ) with multiple circular perforations. The utilized model incorporates restrained out-of-plane displacements along the four edges of the plate. Analyzed plates are subjected to linearly varying in-plane loads to simulate various combinations of axial and flexural stresses. The effect of different geometrical parameters on the elastic buckling load of perforated web plate is investigated. These geometrical parameters include the plate’s length and width, and the perforations’ diameter and spacing. Comprehensive finite element analyses are conducted to identify the behaviour of wide spectrum of perforated web plates at buckling under various combinations of axial compressive load and bending moment. Outcomes of the study are expected to enhance the understanding of the elastic local buckling of web plates of cellular beam–column elements.

Local Buckling Analysis of Aluminum I Section Beams

Low elastic modulus of aluminum alloy gives prominence to lateral and local buckling of members, especially when thin walled sections are adopted to save material usage. Under certain conditions of loads and constraint, local buckling would occur in aluminum beams. A numerical study to assess the local stability of aluminum I section beams is presented in this paper. The study focused on two aspects: the local buckling of aluminum flange plate under compression, the local buckling of aluminum web plate under bending and shear. An extensive parameter analysis including width-to-thickness ratio, initial imperfection, material constitutive relation and restriction effect from adjacent plates was carried out with the purpose of extracting several governing parameters and investigating their effects on the local buckling of aluminum plate. Based upon the results of finite element analysis (FEA), a new design method in connection with the local stability of aluminum I section beams has been developed. By virtue of the proposed design method, three key indicators that include the critical value of width-to-thickness ratio to prevent local buckling of aluminum flange plate under compression, the local stability of aluminum web plate under bending/shear and the bearing capacity of aluminum I section beams under the condition that the post buckling strength of web is taken into account, could be obtained to provide more rational and efficient designs. The proposed design method is different from the current Eurocode but acts in accordance with Chinese code for design of steel structures (Chinese steel code) in order to satisfy applicability.

Test and numerical simulation of partially encased composite columns subject to axial and cyclic horizontal loads

Partial encased composite (PEC) members with thin steel plates and three types of constructional detailing are studied. Six pieces of PEC column specimens were tested under constant vertical load and cyclic horizontal loads. A numerical FE model is established. In the model, the in-filled concrete is decomposed as transverse and longitudinal springs, considering the functions and the properties of the concrete in two directions. This model simplifies the numerical computation with high efficiency, and acquires a satisfied agreement with test results in both capacity and deformability of the PEC member. The parametrical study by the FE model is performed. By tests and numerical analysis, it is found that though local buckling of thin plate of H steel is a crucial factor, when the compressively axial load does not surpass the encased steel capacity, the PEC could behave quite well under cyclic horizontal loads. No distinguished difference in three kind details was observed, so that PEC member could be built in a simple way.

Structural performance of lightweight steel-foamed concrete–steel composite walling system under compression

This paper presents the results of an experimental and analytical investigation on the structural behaviour of a composite panel system consisting of two outer skins of profiled thin-walled steel plates with lightweight foamed concrete (LFC) core under axial compression. The gross dimensions of the test specimens were 400 mm×400 mm×100 mm. A total of 12 tests were carried out, composed of two duplicates of 6 variants which were distinguished by two steel sheeting thicknesses (0.4 mm and 0.8 mm) and three edge conditions of the sheeting. The density of LFC was 1000 kg/m 3. Experimental results include failure modes, maximum loads and load-vertical strain responses. In analysis, full bond between the steel sheets and the concrete core was assumed and the LFC was considered effective in restraining inward buckling of the steel sheets. Using the effective width method for the steel sheets, the load carrying capacities of the test specimens were calculated and compared with the experimental results. It was found that a combination of the Uy and Bradford plate local buckling coefficients with the Liang and Uy effective width formulation produced calculation results in good agreement with the experimental results. Finally, a feasibility study was undertaken to demonstrate the applicability and limit of this new composite walling system in low rise construction.

SLENDER THIN‐WALLED BOX COLUMNS SUBJECTED TO COMPRESSION AND BENDING

This paper deals with tests on slender thin‐walled box columns, susceptible to instability of both types: to global Euler buckling as well as to local buckling of steel plates. Eight full‐scale tests were carried out with different global slenderness of welded and cold‐formed columns subjected to centric and eccentric compression. For the purpose of profound numerical simulations of tests, material properties were also tested, and the initial column geometry and residual stresses were carefully measured. The results of FEA simulations show good agreement with the test results. On verified numerical model the influence of different initial imperfections was studied. Santrauka Straipsnyje nagrinejami liaunuju dežinio skerspjūvio kolonu, jautriu abieju tipu nepastovumui ‐ bendrajam klupumui pa‐gal Euleri ir plieniniu plokšteliu vietiniam klupumui, eksperimentai. Buvo atlikti aštuoni centriškai ir ekscentriškai gniuždomu virintinio ir šaltai lankstyto skerspjūvio ivairaus liaunio kolonu natūriniai bandymai. Siekiant nuodugniai atlikti skaitini bandymu modeliavima, taip pat bandymu nustatytos mechanines plieno savybes ir kruopščiai išmatuoti visi pradiniai geometriniai nuokrypiai ir liekamieji itempiai. Skaitinio modeliavimo baigtiniu elementu metodu ir natūriniu bandymu rezultatai nedaug skiriasi. Tikrinamuoju skaitiniu modeliu buvo nagrinetas ivairiu pradiniu geometriniu netikslumu poveikis.

SEISMIC PERFORMANCE OF SLITTED STEEL PLATES ENCLOSED BY WOOD PANELS

A new-type hysteretic damper composed of a slitted steel plate and buckling-restraining wood panels is proposed. Cyclic loading tests on five damper element specimens, including one without buckling restraining panels, are conducted. The buckling-restrained specimens behave in a stable manner with the equivalent viscous damping ratio ranging from 0.3 to 0.4, while the hysteresis loops after the ultimate strength are pinched due to the steel plate's local buckling in the vicinity of slit ends. In the specimen with the thinnest wood panels, large kinks are formed close to corners of the steel plate, and in another specimen, where cracks are formed between the slits, strength deterioration is observed. Associated FEM analyses that represent the specimens show good agreement with the test results.

Novel Technique for Inhibiting Buckling of Thin-Walled Steel Structures Using Pultruded Glass FRP Sections

The use of composite materials for strengthening the ailing infrastructure has been steadily gaining acceptance and market share. It can even be stated that this strengthening technique has become main stream in some applications such as strengthening concrete structures. The same cannot be said about steel structures; for which research on composite material strengthening is relatively new. Several challenges face strengthening steel structures using composite materials such as the need for high-modulus composites to improve the effectiveness of the strengthening system. This paper explores a new approach for strengthening steel structures by introducing additional stiffness to buckling-prone regions. The proposed technique relies on improving the out-of-plane stiffness of buckling-prone members by bonding pultruded fiber-reinforced polymer (FRP) sections as opposed to the commonly used approach that relies on in-plane FRP contribution. The paper presents results from an experimental investigation where shear-controlled beam specimens were tested to explore the feasibility of the proposed technique. Bar specimens were also tested in tension to compare between in-plane and out-of-plane contributions of FRP to the behavior and strength of thin steel plates. Based on the results, it can be concluded that this strengthening technique has great potential for altering failure modes by delaying the initiation of undesirable local buckling of thin steel plates. Recommendations for future research efforts are made to expand the knowledge base about this unexplored strengthening technique.

Local buckling of steel plates in rectangular CFT columns with binding bars

This paper presents a theoretical study on the elastic local buckling of steel plates in rectangular concrete-filled steel tubular (CFT) columns with binding bars under axial compression. It is assumed that the unloaded edges of the steel plate are elastically restrained against rotation, whereas the loaded edges are clamped. Based on the energy method, the formulas for elastic local buckling strength of the steel plate in rectangular CFT columns under axial compression are derived, which are calibrated with the experimental results. Then the formulas are employed to study the elastic local buckling of steel plates in rectangular CFT columns with binding bars under axial compression. It is shown that the binding bars can increase the local buckling coefficient, which results in improvement of the capacity of the steel plate to resist local buckling. Finally, appropriate spacing of binding bars, appropriate limitation for aspect ratio and corresponding appropriate limitation for width–thickness ratio are suggested for rectangular CFT columns with binding bars under axial compression.

Stability of longitudinally stiffened web plates under interactive shear and bending forces

Local buckling of web plates having a longitudinal stiffener in different positions under simultaneous shear and in-plane bending is investigated. The interaction study is carried out by both numerical simulation of the problem utilizing finite element method, and by an analytical procedure based on energy method using trigonometric functions. Interaction curves show that the existence of small amounts of in-plane bending may increase the shear buckling capacity, and that the introduction of a longitudinal stiffener significantly increases the critical stress of web plates. Also a very good correlation between the proposed energy method and the finite element method is obtained.

Elastic and inelastic local buckling of stiffened plates subjected to non-uniform compression using the Galerkin method

A solution for the elastic and inelastic local buckling of flat rectangular plates with centerline boundary conditions subjected to non-uniform in-plane compression and shear stress is presented. The loaded edges are simply supported, the longitudinal edges may have any boundary conditions and the centerline is simply supported with a variable rotational stiffness. The Galerkin method, an effective method for solving differential equations, is applied to establish an eigenvalue problem. In order to obtain plate buckling coefficients, combined trigonometric and polynomial functions that satisfy the boundary conditions are used. The method is programmed, and several numerical examples including elastic and inelastic local buckling, are presented to illustrate the scope and efficacy of the procedure. The variation of buckling coefficients with aspect ratio is presented for various stress gradient ratios. The solution is applicable to stiffened plates and the flange of the I-shaped beams that are subjected to biaxial bending or combined flexure and torsion and shear stresses, and is important to estimate the reduction in elastic buckling capacity due to stress gradient.

Failure mechanisms for stocky webs under patch loading at elevated temperatures

This paper presents an analytical model for determining the ultimate strength at elevated temperatures of stocky hot-rolled and plate girder webs subjected to patch loading induced by concentrated loads, as would occur in the compressive region of beam-to-column connections in a steel frame building in a fire. The model is based primarily on the formation of idealised plastic hinges in the flanges, which lead to a yield failure mechanism being induced in the member web. Plate local buckling is not considered in the formulation. Two possible yield failure mechanisms that depend on the temperature regime and on the length of the connection in compression are identified, and these are different from the yield failure mechanisms that occur at ambient temperature. A parametric study that is undertaken for a typical connection, based on the simple prescriptive equations developed in the paper, illustrates the variation of the ultimate strength of stocky webs with the variation of the thermal gradient and with the length of the patch load. The results indicate that the response of the connection under fire must be considered for accurate modelling of a steel framed building if a rational fire engineering approach is to be used in design.

On the use of the Lagrange Multiplier Technique for the unilateral local buckling of point-restrained plates, with application to side-plated concrete beams in structural retrofit

Reinforced concrete beams can be strengthened in a structural retrofit process by attaching steel plates to their sides by bolting. Whilst bolting produces a confident degree of shear connection under conditions of either static or seismic overload, the plates are susceptible to local buckling. The aim of this paper is to investigate the local buckling of unilaterally-restrained plates with point supports in a generic fashion, but with particular emphasis on the provision of the restraints by bolts, and on the geometric configuration of these bolts on the buckling loads. A numerical procedure, which is based on the Rayleigh-Ritz method in conjunction with the technique of Lagrange multipliers, is developed to study the unilateral local buckling of rectangular plates bolted to the concrete with various arrangements of the pattern of bolting. A sufficient number of separable polynomials are used to define the flexural buckling displacements, while the restraint condition is modelled as a tensionless foundation using a penalty function approach to this form of mathematical contact problem. The additional constraint provided by the bolts is also modelled using Lagrange multipliers, providing an efficacious method of numerical analysis. Local buckling coefficients are determined for a range of bolting configurations, and these are compared with those developed elsewhere with simplifying assumptions. The interaction of the actions in bolted plates during buckling is also considered.

A simple method for the inclusion of external and internal supports in the spline finite strip method (SFSM) of buckling analysis

The SFSM is an attractive numerical technique for the buckling analysis of folded-plate structures where general loading regimes and boundary conditions need to be modelled. In implementing splines as interpolation functions in the longitudinal direction of the strip, amended splines have been used conventionally to model the variety of end conditions that may occur. These amended splines are fairly difficult to implement, particularly so if internal restraints are also to be specified. A simple technique for replacing the specification of dedicated amended splines is presented in this paper. The method is then employed to study the local buckling of flat plates under longitudinally and transversely varying compression and bending with different boundary conditions at the ends.

Stability and fracture of plates with two edge cracks under tension

The paper presents experimental results on the deformation, local buckling, and fracture of D16AT plates with two parallel edge cracks under tension. The distribution of strains and deflections over typical cross-sections and buckling modes are determined. The influence of the crack length and the distance between the cracks on the local buckling stresses and breaking stresses is studied. The effect of local buckling on the strength of the plate is evaluated

Local buckling and post-local buckling redistribution of stress in slender plates and sections

Cold-formed open steel sections are comprised of component plates termed stiffened elements (webs) and unstiffened elements (flanges). The local buckling and post-local buckling behaviour of sections may be determined from the behaviour of the component plates. Much research effort has documented the theoretical elastic local buckling of plates and sections, however until recently few experimental studies have been reported on the local buckling and post-local buckling behaviour of unstiffened plates. This paper presents experimental and numerical studies of unstiffened plates and sections that contain them in both compression and bending, and in particular analyses the mechanism that provides post-buckling strength. It is shown that, as with stiffened elements, the mechanism is the post-local buckling redistribution of stress, however unlike stiffened elements this redistribution can occur to such an extent that tensile stresses commonly form in axially compressed slender elements. The stress distributions at ultimate are compared with current international cold-formed steel specifications.

Local buckling of steel plates in concrete-filled thin-walled steel tubular beam–columns

The availability of high strength steels and concrete leads to the use of thin steel plates in concrete-filled steel tubular beam–columns. However, the use of thin steel plates in composite beam–columns gives a rise to local buckling that would appreciably reduce the strength and ductility performance of the members. This paper studies the critical local and post-local buckling behavior of steel plates in concrete-filled thin-walled steel tubular beam–columns by using the finite element analysis method. Geometric and material nonlinear analyses are performed to investigate the critical local and post-local buckling strengths of steel plates under compression and in-plane bending. Initial geometric imperfections and residual stresses presented in steel plates, material yielding and strain hardening are taken into account in the nonlinear analysis. Based on the results obtained from the nonlinear finite element analyses, a set of design formulas are proposed for determining the critical local buckling and ultimate strengths of steel plates in concrete-filled steel tubular beam–columns. In addition, effective width formulas are developed for the ultimate strength design of clamped steel plates under non-uniform compression. The accuracy of the proposed design formulas is established by comparisons with available solutions. The proposed design formulas can be used directly in the design of composite beam–columns and adopted in the advanced analysis of concrete-filled thin-walled steel tubular beam–columns to account for local buckling effects.