Local Buckling Resistance Research Articles

Eccentric compression behavior of CFRP-confined reactive powder concrete-filled steel tube slender columns

Ultra high and large-span structural components are needed in urban modernization construction to meet the engineering requirements. Reactive powder concrete-filled steel tubes (RPCFSTs) provide a cost-effective and efficient solution for optimizing space utilization in super high-rise buildings and enhancing the crossing capacity of bridge, which accords with such development. However, these components have inherent drawbacks in terms of local buckling and corrosion resistance. The use of carbon fiber reinforced polymer (CFRP) confinement to suppress this innate deficiency has been proven to show great advantages in limited trial results. This article establishes a comprehensive test scheme to investigate the eccentric compression performance of CFRP-confined RPCFST columns. A total of 11 specimens were prepared and subjected to biased compression test by varying the component length (400, 800, 1200, and 1600 mm), number of CFRP layers (0–3), and load eccentricity (0, 10, 20, 30, and 40 mm). The results showed that the CFRP confinement could effectively enhance the bearing capacity and energy dissipation capability of RPCFST columns while delaying the local buckling of slender specimens with low slenderness ratios. The improvement of ultimate load due to CFRP confinement exceeded 42.5 %. However, in specimens with higher slenderness ratios and with increasing load eccentricity, the confinement effect of the steel tube on the core RPC tended to weaken. An N–M interaction model for slender CFRP-confined RPCFST columns was established, and this model was validated to be in good agreement with the experimental results. The conclusions drawn from this study might given a solid foundation for the future application of CFRP-confined RPCFST structures.

Thin-walled FRP-concrete-steel tubular tower with a top mass block subjected to lateral impact loading: Experimental study and FE analysis

Thin-walled hollow steel tube towers (HSTs), frequently utilized as a wind turbine tower, are facing challenges such as corrosion and local buckling in their service life. To enhance the anti-corrosion capacity and local buckling resistance, an FRP tube and an annular concrete layer can be employed to protect the HST, thus forming a novel member: thin-walled FRP-concrete-steel tubular towers (TW-FCSTs). Using a horizontal vehicle impact system, this study investigated the impact behavior of five large-scale TW-FCSTs, each with a top mass block to mimic the rotor and nacelle of wind turbine. All specimens were designed with a large diameter (300 mm) and a large void ratio (0.73 or 0.82). The experimental results revealed that: (1) Under lateral impact loading, TW-FCSTs displayed a global flexural failure mode, accompanied by localized concavity damage; (2) The inertial effect was enlarged by the top mass block, affecting the dynamic response of TW-FCSTs; (3) the increase of steel thickness led to higher energy dissipation but lower local deformation; (4) the increase of void ratio resulted in larger local deformation but smaller lateral global displacement. Finally, based on LS-DYNA, FE models were utilized to simulate the dynamic responses of TW-FCSTs with a top mass block.

The Performance of Cold-Formed Steel Beam-Column Connections with Screw Configuration

Cold-formed steel is being used as a viable substitute for traditional steel and building materials due to its performance, affordability, convenience, lightweight, and environmental friendliness. The major purpose of this current research is for a reaction to force-deformation at the connection level to be delivered, which is proper for typical cold-formed steel (CFS) screwed beam-column assembly CFS C-section, and to show the influence of the behavior of CFS under bending test. An inner plate, double angle plate, and self-drilling screws are used by a basic beam-column frame idealized CFS to join the beam-column. Fixed support was implemented at the column base, whereas the beam end had free support. A 0.75 mm cold-formed steel C-section with 80mm height and 30mm width was utilized in this study and assembled into an "I" and "box" configuration. 3d and 4d were used to compute screw spacing for self-drilling screws with 4 mm heads and 2 mm bodies. The first type was each angle plate (top and seat angle) screwed with eight screws, whereas the second involves four screws. The CFS section’s thinness led to the use of screw connections, which are essential to their ability to withstand connection failures, to anticipate the failure mode of the connection segment. Numerical simulation by ABAQUS Student Edition and analytical studies have been conducted by AS/NZS 4600:2018 to investigate the capacity of CFS under bending. Quantity and the arrangement of the screws determine the displacement ductility with tighter spacing enhancing performance and reinforcing global and local buckling resistance.

Monte Carlo Simulations for Global and Local Interaction Buckling of Welded Box-sections

The present study focuses on investigating the interaction behavior of local and global buckling resistance of welded box-section columns by using stochastic analysis. Previous studies mainly investigated this failure mode using experimental or numerical investigations but using deterministic approaches. The current research employs Monte Carlo simulations as a robust numerical tool to estimate the interaction buckling resistance. Stochastic variables are defined, encompassing variabilities in geometrical and material properties, as well as local and global imperfections. To facilitate these simulations, a rigorously validated numerical model is employed, utilizing geometrical and materially nonlinear analysis with imperfections (GMNIA). This advanced modeling approach accounts for the complex nonlinearities inherent in the behavior of welded box-section columns. The characteristic resistance derived from the Monte Carlo simulation is compared to 1. test results, 2. analytical buckling resistance according to the Eurocode design approach, and 3. previously proposed deterministic approaches. Within the research program, an improved generalized design formula is developed to estimate the buckling resistance for pure local, global, and interaction buckling modes. The new design equation is compatible with the design rules of the Eurocode and enhances the ease of use of the standard regulations.

Behavior of eccentrically loaded rectangular CFST components for shear walls using double horizontally-corrugated steel plates

The utilization of corrugated steel plates in concrete filled steel tube (CFST) structures has shown advantageous performance and considerable economy due to their high out-of-plane stiffness and local buckling resistance. A novel composite shear wall composed of multiple CFST components using double horizontally-corrugated steel plates and connected using pure corrugated steel plates with large wave heights was proposed. Fifteen CFST components with double horizontally-corrugated steel plates were designed and statically tested to evaluate the eccentric compression performance. Parameters including nominal eccentricity ratios, nominal sectional aspect ratios, steel plate thicknesses, and diameters of reinforced longitudinal reinforcements were considered. The bearing capacity, stiffness, and ductility of the CFST component with double horizontally-corrugated steel plates were investigated. In addition, the non-uniformities of confinement along with cross-sectional depth was studied through the analysis of measured strains and finite element simulations. Moreover, two capacity models of the eccentrically loaded components were proposed based on eccentricity reduction coefficient and stress balance of the cross-section, respectively. Both models effectively predicted the experimental and simulated results.

Residual stresses in steel I-sections strengthened by wire arc additive manufacturing

Wire arc additive manufacturing (WAAM) is a method of metal 3D printing that can be used to complement traditional steel manufacturing techniques (e.g. hot-rolling and cold-forming), to produce hybrid structural elements of enhanced efficiency. The case of hot-rolled steel I-sections strengthened by the addition of WAAM stiffeners at the flange tips is the focus of the present study. In addition to the improved local buckling resistance and increased flexural rigidity achieved by the addition of the stiffeners, a further source of enhanced load-bearing capacity arises from the inversion, through thermal action, of the adverse residual stress pattern typically associated with hot-rolled I-sections. Thus, in contrast to previous studies, the aim of the present investigation is not to eliminate but to take benefit from residual stresses, by prestressing (pretensioning) specific parts (i.e. the flange tips) of steel sections against subsequent applied compressive loading, thereby delaying yielding and enhancing the load-bearing capacity. The described hypothesis is demonstrated in the present study through the manufacture of a series of hybrid WAAM-strengthened hot-rolled I-sections and the subsequent performance of residual stress measurements. Stiffeners of different dimensions were printed using ER70S-6 welding wire. A detailed description of the adopted experimental technique, which utilised the sectioning method, is provided, while the magnitude and distribution of the measured residual stresses are reported. The addition of WAAM stiffeners at the flange tips of hot-rolled I-sections is shown to lead to the generation of desirable (for structural stability) tensile residual stresses in their vicinity, with peak values reaching the yield strength of the material; self-equilibrating compressive residual stresses are induced in the web and around the web-to-flange junction.

Design and analysis of buckling-induced honeycombs with tailorable out-of-plane crushing performance

Novel honeycombs with buckling-induced features and tailorable properties have been designed and fabricated using the fused deposition modeling (FDM) method. Quasi-static out-of-plane compression tests were carried out to investigate the topological dependence of the crushing behavior of the buckling-induced honeycombs (BIHs). The results demonstrated that the crushing performance of BIHs can be artificially controlled by altering their shape parameters. In particular, the initial peak force (IPF) and the undulation of the mechanical response of BIH can be effectively reduced by increasing the layer number or arranging the asymmetric layers. A finite element model validated against experimental results was also utilized to reveal the underlying deformation mechanism and study the corresponding displacement-crushing force responses for BIHs with different topological parameters. It was uncovered that the buckling-induced mechanism is beneficial for tuning the stiffness and mitigating local buckling resistance through the pre-determined collapse behavior of cell walls. Further, a multi-objective optimization process of BIH was performed to seek the optimal design solution for energy-absorbing structures in specific scenarios. The findings of this study provide a theoretical basis for the development of new ideas and optimization solutions for the design of lightweight and performance-tailored energy-absorbing structures.

Axial compressive behavior of cold-formed steel built-up box-shape columns with longitudinal stiffeners

This paper presents a study on the behavior of cold-formed steel built-up box-shape columns with longitudinal stiffeners (CFS-BCL) under axial compression. The specimens are fabricated using a pair of channel sections and lipped channel sections with longitudinal stiffeners, which are expected to enhance the local buckling resistance of the web. Sixteen specimens were prepared for compression tests, with varying lengths and screw arrangements. Prior to the tests, initial geometric imperfections of the specimens, material properties, and shearing-resistance behavior of the screw fasteners were measured. The results indicate that screw arrangements have a significant effect on simply supported specimens; reducing the screw spacing from 300 mm to 100 mm can increase load-bearing capacity by up to 11%. Finite element models were developed using ABAQUS and validated against test results. The parametric analysis revealed that screw arrangements had minimal impact on the local buckling capacity of specimens, with an increase in capacity of <8%. However, global buckling behavior was significantly affected by screw arrangements, resulting in an increase in capacity of up to 20% for slender columns. The test and analytical results were compared with the Direct Strength Method (DSM), and indicate that the DSM is conservative when the non-dimensional slenderness ratio λg and λl is higher than 1.2 and 1.4, respectively. The coefficients of the DSM were modified based on the test and simulation results, and its predictive accuracy was found to be highly increased.

Local buckling of WAAM stainless steel circular columns

AbstractWire and Arc Additive Manufacturing (WAAM) is one of the promising metal 3D printing techniques, with the ability to produce large‐scale structural components with high speed and low cost. However, there is a lack of research on the structural performance of WAAM members. To this end, numerical modeling and design of WAAM stainless steel circular hollow section (CHS) stub columns has been conducted. Finite element (FE) models considering both as‐built material properties and rough geometry were proposed and verified by the existing experimental studies. By using the FE models, parametric studies on the local buckling resistance of WAAM CHS stub columns were conducted to consider a wider range of specimen geometries. Based on the FE results, the applicability of the current column design provisions in EN 1993‐1‐4 and AISC 370 to WAAM stainless steel CHS stub columns was assessed. At last, a new modified method was proposed to predict the local buckling resistance of WAAM stainless steel CHS stub columns. This study provides a novel approach for the FE modelling of WAAM components.

Seismic performance of corrugated steel plate composite shear walls with various configurations

This article proposed a novel form of composite shear wall composed of a concrete-filled corrugated steel tubular column frame and an infilled corrugated steel plate. This innovative design leverages the excellent out-of-plane stiffness and local-buckling resistance of corrugated steel plates. Quasi-static tests and numerical simulation analysis were conducted on eight composite shear walls. The tests focused on various parameters, including the arrangement of infilled steel plates, the orientation of corrugations, and the presence of openings. The specimens were evaluated for failure modes, hysteresis curves, stiffness degradation, and energy dissipation capacity. The research results indicate that this composite structure exhibited favorable seismic performance, with failure modes observed as yielding of the inner infilled plate and plastic hinge failure of the column bases. The specimens achieved an ultimate drift ratio about 1/50. Additionally, finite element models were employed to analyze the stress distribution within the structure.

Lattice structure design optimization under localized linear buckling constraints

An optimization method for the design of multi-lattice structures satisfying local buckling constraints is proposed in this study. In order to resolve the highly nonlinear large-scale optimization problem, a consecutive numerical approach is devised: macro-field optimization and microstructure embedding. The macro-field optimization finds an optimal elasticity tensor distribution among all feasible elastic continua based on a concept of free material optimization (FMO), which largely extends the design space compared with density-based topology optimization. After this, by an inverse design approach that approximates the elasticity tensor under local buckling constraint, an appropriate lattice structure is able to be embedded within each macro-element, where the local stress tensors are considered in particular to produce more reasonable microstructures. During the process, a machine learning approach is also devised to significantly reduce the number of material/lattice types and thus the overall computational costs. Ultimately, a lattice structure under requirements of overall stiffness and local buckling resistance is produced, as demonstrated via numerical examples.

Local buckling resistance of bamboo scrimber plates in compression

This paper describes experimental and theoretical investigations on behaviour of short bamboo scrimber box columns under compression. In the experimental programme, six groups of short columns with different width-to-thickness ratios of plates were tested and the load capacity and failure modes of the columns were determined. Test results indicated that when the width-to-thickness ratio of plates was less than or equal to 10, box columns exhibited compression failure and the ultimate compressive strength of bamboo scrimber was reached at failure. However, local buckling of bamboo scrimber plates was observed instead of compression failure once the width-to-thickness ratio of plates exceeded 11, and the ultimate compressive stress decreased with increasing width-to-thickness ratio. Based on the experimental data, theoretical analyses were also performed by considering the nonlinear stress-strain relationship to quantify the buckling stress of bamboo scrimber plates with four simply-supported edges. Comparisons between experimental and theoretical results suggest that when the theoretical equation yields reasonably good estimations of the local buckling stress of columns with the width-to-thickness ratio of plates greater than 10.

Determination of local buckling resistance of Fiber-reinfoced composite column having material imperfection by nonlinear buckling analysis

The pultruded Fiber Reinforced Polymer (PFRP) material manufactured by the “pultrusion” process has many applications in the construction industry. However, the production process involves several difficult-to-control stages, which can lead to material defects. This paper proposes a method to determine the local buckling resistance of FRP composite I column having material imperfection on the flanges and web. The research has shown that the buckling load determined in nonlinear buckling analysis is 15.5% higher than that obtained from eigenvalue solution (linear perturbation analysis). In addition, the post-buckling resistance of the column is 66.4% higher compared to the local buckling load. The author suggests that this modelling and determination method be widely applied to PFRP structures when studying the instability of columns or beams under various loadings and boundary conditions and different combinations of defects.

Local buckling resistance of Pultruded FRP columns: Theoretical predictions vs. Experimental study

Fiber-Reinforced Polymer (FRP) in the form of thin-walled plate structures are widely used in different engineering applications due to their outstanding features such as: high strength-to-weight ratio, excellent fatigue and corrosion resistance, etc. Due to the low stiffness, design of FRP material is usually governed by deformations or instabilities, rather than strengths. The development of a technical specification for design of FRP composite structures requires the understanding on buckling behaviour of FRP components. Local buckling of pultruded FRP column is a type of structural instabilities, occurs when the compressive stress reaches to the level that form waves in the flanges or web plates, causing the plastic deformation in the fiber which ultimately reduces its strength and stiffness. This study focuses on the local buckling resistance of pultruded FRP columns by experimental work. The test data were compared to current theoretical and numerical predictions. It is found that the difference of &lt;15% between experiment and predictions can be acceptable. The author recommends that the Kollar’s equations to be used when predicting local buckling of Pultruded FRP column of I or channel shapes.

The Eccentric Compression Performance of Spirally Stiffened Thin-Walled Square Concrete-Filled Steel Tubular Laminated Composite Members

To enhance the local buckling resistance of thin-walled steel pipes and enhance their fire and corrosion resistance, a new spirally stiffened thin-walled square concrete-filled steel tubular laminated composite member with transverse ribs is proposed. Through the four forms of combined members for eccentric pressure testing, it was found that: ordinary thin-walled steel pipe concrete drum buckling is more severe; with spiral ribs, the buckling is limited between the stiffening ribs; and the deformation is significantly reduced. By addressing the problem of cooperative work between the inner and outer structural layers of new components, it was found that, after setting constraints such as steel bars, the integrity of the two can be ensured, and the stress performance is significantly improved; compared to ordinary steel pipe concrete, the load-carrying capacity is 17.9% higher, and the deformation capacity is roughly equivalent. Spiral ribs as a new form of spatial restraint, in addition to increasing the local bending stiffness, manifest an overall restraint role in limiting lateral deformation of the steel pipe, whereas the role of vertical stiffness is insignificant. Based on test evidence, the influences of the width to thickness ratio of spiral ribs and pitch were determined, and reasonable structural measures for the members were given. Through the N–M relationship curve, the limit of damage in compression and tension under eccentricity was obtained at an eccentricity of about 0.9. Finally, a method for calculating the eccentric compressive ultimate load capacity of this new composite member was proposed.

Flexural behavior of prestressed concrete-filled steel tubular flange beams

This research presents a numerical and analytical investigation on the structural characteristics of concrete-filled steel tubular flange beams (CFSTFBs) prestressed using steel strands under bending. CFSTFBs are found to benefit from higher flexural and shear strength compared to those of I-section beams with flat flanges. The geometrical configurations of these sections provide them with higher web local buckling resistance due to a larger flange depth-to-width ratio. A large number of existing structures, constructed with steel–concrete composite beams, need to be retrofitted due to many factors such as loss of strength as a result of service loads and environmental conditions. A potentially economical and feasible approach to strengthening these beams is upgrading them using steel prestressing strands. The finite element (FE) approach was utilized to develop a three-dimensional numerical model considering both material and geometrical nonlinearity. Accordingly, the effects of concrete strength, tubular flange shape and dimension, steel yield stress, and quantity and eccentricity of strands were included in the analysis. A simplified model, on the basis of the plastic stress distribution method (PSDM), was used to estimate the ultimate moment capacity. In order to visualize the influence of steel and concrete strength and tubular flange size on the moment capacity of CFSTFBs, several artificial intelligence (AI) algorithms were employed and a partial dependence analysis was also conducted accordingly. The ultimate capacities obtained by analytical and FE models, considering the effect of confinement, were verified by comparing the predictions with the results from experimental studies. Both analytical and FE results indicated that the prestressing strands are significantly capable of enhancing the stiffness and strength of CFSTFBs under flexural loading. It was demonstrated that the tube geometric properties can significantly control the overall performance of prestressed CFSTFBs. The results also indicated a negligible effect of the concrete compressive strength.

Flange Local Buckling Resistance and Local–Global Buckling Interaction in Slender-Flange Welded I-Section Beams

AISC Specification Chapter F characterizes the flange local buckling (FLB) strength of I-section members having a slender compression flange as the theoretical elastic plate local buckling resistance, ignoring beneficial local post-buckling strength. Previous research has shown that this results in highly conservative strength predictions for slender-flange members. Additionally, potential interaction between local and global lateral-torsional buckling modes is not considered in the AISC Specification. These aspects can be important in applications involving the use of slender-flange members. This paper investigates a number of potential methodologies to account for local post-buckling strength as well as local–global buckling interaction in beams having slender flanges. A parametric finite element analysis (FEA) study is conducted considering a range of I-section members. The strength predictions from the proposed methodologies and the AISC Specification are evaluated against the FEA results as well as against a database of measured strengths from previous experimental tests of I-section beams governed by FLB. Recommendations are provided focusing on simplicity of the calculations and the efficacy of their predictions.

Cyclic behavior of concrete-filled square tubular columns with stiffened plastic hinge region

The seismic behavior of concrete-filled square steel tube (CFST) columns is greatly influenced by the local-buckling of steel tubes within the plastic hinge region. This paper focuses on a novel stiffener that strengthens the potential plastic hinge regions to enhance the local-buckling resistance of steel tube, hence improving the overall seismic performance of the CFST columns. To verify its effectiveness and investigate the hysteretic behavior of the stiffened CFST (referred to as SCFST) columns, three CFST and three counterpart SCFST columns were fabricated and tested under cyclic lateral load while subjected to constant axial load. Furthermore, flexural capacities calculated using representative design equations in current codes as well as a newly proposed method were compared with the experimental results. Calculation method for the effective strengthening length of SCFST was presented. The test and analytical results showed that: (1) this stiffeners could effectively delay the local buckling of steel tube and change its local buckling modes; (2) the stiffener significantly enhanced the lateral load capacity of SCFST columns with improvement of 14%, 15%, and 38% comparing with the counterpart CFST columns; (3) the thinner the steel tubes, the more significant the effect of the stiffener on the ultimate lateral capacities; (4) the design equations prescribed in current codes tended to underestimate the ultimate flexural strength of SCFST columns with a discrepancy between 22% and 60%; (5) the proposed calculation method taking account of the effect of the stiffener, could more accurately predict the flexural strength of SCFST columns than current design equations with an improved discrepancy ranging between 7% and 32%.

Local plate buckling type imperfections for NSS and HSS welded box-section columns

The finite element model-based design of steel structures is getting increasing attention by designers, especially in the case of buckling problems of welded plated structures and by the static check of the interacting stability behaviour. The FEM-based design approach is introduced and standardised in the EN 1993–1-5 Annex C providing the ability to calculate the buckling resistance based on direct resistance check by geometrical and material non-linear analysis using imperfections (GMNIA). By this design process, the application of imperfections (shape and magnitude) has a large impact on the computed buckling resistance. It is especially true if the interacting stability phenomenon (interaction of plate and column-like behaviour) is to be analysed. The general way to consider imperfections in FE models is the application of equivalent geometric imperfections covering the effect of residual stresses and geometric imperfections. Several previous investigations prove the application of equivalent geometric imperfections can lead to conservative resistance, especially in the case of the interacting stability problem because the application of two different equivalent geometric imperfections leads to duplication of the residual stresses. Therefore, it is highly important to determine the appropriate imperfection shape and size for buckling problems. The current paper deals with the determination of local plate buckling-type imperfection, which can be further applied in numerical models used for interacting stability problems, which is the next step of the planned research program. Within the current paper, the necessary imperfection magnitudes are determined for welded square box-section columns for various steel grades (S235 – S960) to perfectly match the local buckling resistance proved by test results and gives design proposals for FEM-based design approaches.

Equivalent Geometric Imperfections for Local Buckling of Slender Box-section Columns

Determining the plate or the local buckling resistance is highly important in designing steel buildings and bridges. The EN 1993-1-5Annex C provides a FEM-based design approach to calculate the buckling resistance based on numerical design calculations (geometrical and material nonlinear analysis - GMNIA). Within the GMNIA analysis-based stability design, the application of the imperfections has a special role. Thus, the applicability of the EN 1993-1-5 based buckling curve (Winter curve) has been questioned for pure compression, and previous investigations showed the buckling curve of EN 1993-1-5 Annex B is more appropriate for the design of slender box-section columns subjected to pure compression, the magnitude of the equivalent geometric imperfection to be applied in numerical models for local buckling is also questioned and investigated by the authors within the current paper. The aim of the current research program is to investigate the necessary equivalent geometric imperfections to be applied in FEM-based design calculations using GMNIA calculations. A numerical parametric study is executed to investigate the imperfection sensitivity of box-section columns having different local slenderness. The necessary imperfection magnitudes are determined to each analyzed geometry leading to the buckling resistance predicted by the standardized buckling curves. Based on the numerical parametric study, a proposal for the applicable equivalent geometric imperfection magnitude is developed, which conforms to the plate buckling curves of the EN 1993-1-5 and giving an improvement proposal to the local buckling imperfection magnitudes of the prEN 1993-1-14, which is currently under development.