Aluminum Alloy Columns Research Articles

Stability of 6082-T6 aluminum alloy columns under axial forces at high temperatures

In this study, the material and stability of 10 axial compression aluminum alloy columns are systematically tested at five temperatures. The material grade of the aluminum alloy used in the tests is 6082-T6. The experimental results demonstrate that flexural buckling occurs in all the column specimens under different temperature environments. A finite element (FE) model of the experiment is established, and the obtained results are compared with the experimental results to verify the accuracy of the FE model. To study the stability at different temperatures, 765 FE models considering geometry and material nonlinearity are created in five different temperature environments. Three section types (H-type, rectangular, and circular tube sections), three sectional dimensions for each section type, and 17 slenderness ratios are considered in the models. Based on the FE results and the statistical regression method, the formula for calculating the stability coefficient for the columns with different slenderness ratios at different temperatures is fitted. The fitting formula is compared with the test results, Chinese Code (GB), and European Code (EC9). The comparison results demonstrate that the fitting formula can provide a more accurate stability coefficient for the columns at different temperatures.

Training of ANFIS with simulated annealing algorithm on flexural buckling load prediction of aluminium alloy columns

In this study, we propose a simulated annealing algorithm (SA) to train an adaptive neurofuzzy inference system (ANFIS). We performed different types of optimization algorithms such as genetic algorithm (GA), SA and artificial bee colony algorithm on two different problem types. Then, we measured the performance of these algorithms. First, we applied optimization algorithms on eight numerical benchmark functions which are sphere, axis parallel hyper-ellipsoid, Rosenbrock, Rastrigin, Schwefel, Griewank, sum of different powers and Ackley functions. After that, the training of ANFIS is carried out by mentioned optimization algorithms to predict the strength of heat-treated fine-drawn aluminium composite columns defeated by flexural bending. In summary, the accuracy of the proposed soft computing model was compared with the accuracy of the results of existing methods in the literature. It is seen that the training of ANFIS with the SA has more accuracy.
 
 Keywords: Soft computing, ANFIS, simulated annealing, flexural buckling, aluminium alloy columns.

Experimental and Numerical Investigation on Load-Bearing Performance of Aluminum Alloy Upright Column in Curtain Walls under Wind Pressure

In this paper, the wind resistance performance test and numerical simulation analysis of aluminum alloy columns with different structural measures in unit glass curtain walls are carried out. The two-layer experimental model were composed of 12 unit curtain walls, of which there are 2 beams at a distance of 1.2 m from the top and bottom in 9 unit curtain walls respectively, and there is only one beam at a distance of 1.2 m from the top in 3 unit curtain walls. The dimension of each unit curtain wall is 1.2 m × 4.0 m. The section shape of the experimental model is L-shaped. Firstly, the experimental investigation and analysis of the model with arrangement of one pair of hooks under positive and negative wind were carried out. Secondly, the experimental investigation and analysis of the model with no hooks under positive and negative wind were carried out. The out-of-plane deformation, in-plane deformation and the strain of the columns were collected and analyzed. Finally, finite element analysis model was established. The similarities and differences of the analysis results and the experimental results were analyzed. The results show that the beam has a small constraint on the columns whether the wind pressure is positive or negative when the number and position of hooks are reasonable. When the wind pressure is negative, the hook has little effect on the out-of-plane deformation and stability. Under the action of positive wind, the hooks can significantly reduce the in-plane deformation and restrain the lateral torsion deformation of the columns.

Numerical investigation and design of perforated aluminium alloy SHS and RHS columns

This paper describes a numerical investigation on perforated aluminium alloy square and rectangular hollow section (SHS and RHS) columns by the finite-element analysis (FEA). The non-linear finite-element model (FEM) was developed by considering both geometric and material non-linearities. The initial local and overall geometric imperfections of aluminium alloy columns were incorporated in the FEM. The non-linear FEM was verified against the corresponding experimental results, which was further used for an extensive parametric study that consisted of 594 specimens with different cross-section dimensions, overall lengths, as well as diameters, numbers and locations of circular openings. The ultimate strengths of the columns obtained from FEA were employed to evaluate the current design specifications for aluminium alloy and cold-formed steel structures. It is demonstrated that American Specification (AA) and limit state design (LSD) in Australian/New Zealand Standard (AS/NZS) are somewhat unconservative, whereas allowable stress design (ASD) in Australian/New Zealand Standard (AS/NZS) and Chinese Code are quite conservative, while European Code (EC9) is generally appropriate for imperforated aluminium alloy columns. In addition, North American Specification (NAS) and direct strength method (DSM) for cold-formed steel structural members with openings are quite conservative for aluminium alloy columns with circular openings. The design equations proposed based on the design rules of EC9 were verified to be accurate for perforated aluminium alloy SHS and RHS columns under axial compression.

Buckling behaviors and ultimate strengths of 6082-T6 aluminum alloy columns under eccentric compression – Part I: Experiments and finite element modeling

Aluminum alloys, which function as load-bearing components or decorative materials, have been commonly applied to architectural structures. In this study, a combination of experiments and finite element analyses was conducted to investigate the stability behaviors and ultimate strengths of the 6082-T6 aluminum alloy columns subjected to eccentric compression. Prior to the loading tests, tensile coupon tests and measurement of the initial geometric imperfections for the columns were performed. The buckling behaviors of 30 pin-ended specimens, including 11 extruded square hollow section (SHS) columns and 19 extruded circular hollow section (CHS) columns, were investigated and the observed failure modes of the tested columns included overall buckling, local buckling and the coupling modes. Meanwhile, the ultimate strengths, deflections and surface strains in whole process under eccentric compression were recorded. The finite element (FE) models of the tested columns were developed using the non-linear finite element analysis (FEA) software ABAQUS, and the geometric and material nonlinearities were considered in the FE models. The validation of the FE models was performed against the test results; it was observed that the proposed FE models are sufficiently accurate to predict the ultimate strengths and buckling behaviors of the tested columns.

Buckling behaviors and ultimate strength of 6082-T6 aluminum alloy columns with square and circular hollow sections under eccentric compression – Part II: Parametric study, design provisions and reliability analysis

The wide application of aluminum alloys has been spread in the field of civil and building engineering due to their excellent performance and advantages. The companion paper (Part I) has described the eccentrically compressive loading tests and the verification of finite element (FE) models. In this paper, a parametric study about the 6082-T6 aluminum alloy columns of square and circular hollow sections (SHS-CHS) subjected to eccentric compression was performed using the verified FE models. The key parameters affecting the buckling behaviors and ultimate strength were investigated, including the regularized slenderness ratio, eccentricity, width-thickness ratio (for SHS columns) and diameter-thickness ratio (for CHS columns). The ultimate strength obtained from the previous loading tests and the finite element analysis (FEA) were compared with the design strength predicted by the current Chinese (GB 50429), European (Eurocode 9), American (AA-2010) design codes for aluminum alloy structures. In addition, the newer proposed design method – the direct strength method (DSM), were also investigated. It was found that these four design provisions were generally conservative for predicting the ultimate strength of the SHS and CHS columns for 6082-T6 aluminum alloy and DSM was shown to provide more accurate strength predictions than the current design codes. Finally, the optimal distribution types of the model error (ME) in the four design provisions were investigated and reliability analysis was conducted under different load ratios to evaluate the safety levels of the three current design codes and DSM. Revised Chinses code was proposed to predict the ultimate strength of 6082-T6 aluminum alloy columns more precisely.

ANALYSIS OF BUCKLING AND BENDING FAILURE OF ALUMINIUM COLUMN SECTIONS USED IN EMERGENCY RESTORATION TOWERS

This paper presents an experimental analysis of buckling and bending failure modes of a 2.58 m long, 460×460 mm2 6061-T6 Aluminum alloy column section used in emergency restoration towers. The main objective is to determine the bending and buckling load capacities of the column section through experiments, as these values are critical in an emergency tower (guyed mast) design. Within the context of this overarching goal, a secondary objective is to ascertain whether the presence of certain manufacturing non-conformance affects the loading capacity of the section significantly. Finally, finite-element analysis (FEA) simulations are conducted in order to compare the experimental data with numerical results. The results show that the ultimate bending and buckling load capacities of the column section are 383 kN and 3,868 kN respectively. Furthermore, the results indicate that the presence of manufacturing non-conformances such as air bubbles and delamination do not have a detrimental effect on the load capacity of the column. Of the two non-conformances studied, the specimen with bubbles had a 1% difference from the good specimen, and the delaminated specimen had a 10% deviation. Comparison of experimental data with FEA simulation results shows that the numerical solution tends to overestimate the stiffness of the column, and that the FEA approach may require further calibration.

Behaviour of aluminium alloy plain and lipped channel columns

Aluminium alloys have high strength-to-weight ratios and great durability; thus, they have been extensively used in structural applications. Channel sections have a smooth and aesthetically pleasing line shape, good integrity, and are easy to connect. An experimental program using 28 specimens and a numerical study that generated 100 results were conducted on aluminium alloy columns of plain and lipped channel sections. The nominal length of columns ranged from 300 mm to 3000 mm. The generated 128 results were evaluated with respect to the existing design specifications from America, Australia/New Zealand, Europe and China. Furthermore, the direct strength method (DSM) and the continuous strength method (CSM) were also used to predict results for comparison. The results showed that the design specifications produced conservative compression strengths of aluminium alloy columns of both plain and lipped channel sections. The CSM provided more accurate and consistent design strengths. In addition, the reliability levels of the four international design codes, DSM and CSM for channel sections of aluminium alloy columns were also evaluated.

Torsional buckling and post-buckling of columns made of aluminium alloy

• The closed-form analytical solution of torsional buckling load is derived. • The initial post-buckling behaviour is presented. • The non-linear differential equation of torsional buckling is derived and solved. • The effect of non-linear elastic material with comparison to linear one is discussed. • Comparison of analytical results to FEM analysis is presented. The paper concerns torsional buckling and the initial post-buckling of axially compressed thin-walled aluminium alloy columns with bisymmetrical cross-section. It is assumed that the column material behaviour is described by the Ramberg–Osgood constitutive equation in non-linear elastic range. The stationary total energy principle is used to derive the governing non-linear differential equation. An approximate solution of the equation determined by means of the perturbation approach allows to determine the buckling loads and the initial post-buckling behaviour. Numerical examples dealing with simply supported I-column are presented and the effect of material elastic non-linearity on the critical loads and initial post-buckling behaviour are compared to the linear solution.

Buckling behaviour of aluminium alloy columns under fire conditions

This paper presents a systematic investigation on the buckling behaviour of aluminium alloy columns under fire conditions. One hundred and eight aluminium alloy columns, including sixty rectangular tubes and forty eight circular tubes, were tested under axial load at elevated temperature and at ambient temperature as reference. All the column specimens failed by flexural buckling. Finite element (FE) models implemented in the non-linear code ANSYS were established and verified against the experimental results. To develop a further understanding, 8829 FE models considering geometrical and material nonlinearity were conducted with four kinds of material properties, thirty four kinds of sections and five elevated temperature points. According to the FE results and statistical regression method, formulae to estimate the stability coefficients of aluminium alloy columns under fire conditions were proposed. Finally, the proposed formulae were compared with the experimental results and the stability coefficients from existing codes. It is found that the proposed formulae can provide accurate stability coefficients of aluminium alloy columns under fire conditions.

Experimental investigation and parametric analysis on overall buckling behavior of large-section aluminum alloy columns under axial compression

Experimental investigation was conducted on large-section extruded aluminum alloy columns of I-section and rectangular hollow section (RHS). Altogether seven columns with different slenderness ratios were comprised. The failure modes and stability resistance as well as load-displacement responses were identified. It was found that all tested specimens failed in flexural buckling. An extensive parametric analysis on 180 specimens was carried out with general FEA software ANSYS to evaluate the reliability level of the current design specifications including American aluminum design manual, Eurocode 9 and Chinese code GB 50429. The design stability resistance advised by Eurocode 9 and Chinese code GB 50429 is conservative, while that of American aluminum design manual slightly overestimates the practical stability resistance. Based on the parametric analysis results, a new design method was proposed to improve the design accuracy.

Behaviors and design method for distortional buckling of thin-walled irregular-shaped aluminum alloy struts under axial compression

Since an aluminum alloy structural component can be manufactured through extrusion technology, the cross section can easily comprise various longitudinal stiffeners to strengthen the thin wall and to hold the partition wall panel. In this paper, experimental and numerical investigations on distortional buckling behaviors of thin-walled irregular-shaped aluminum alloy stub columns under axial compression were carried out. Initial geometric imperfections of six extruded aluminum alloy columns were measured using LVDT. The ultimate strength, failure deformation, out-of-plane displacement and strain development of six test specimens were recorded and used to verify a Finite Element Model (FEM) developed by the finite element software ABAQUS. The open plates in the irregular-shaped section had low distortional buckling resistance, which causes the premature failure of the studied columns. 117 columns with different length and plate thickness were numerically simulated by the verified FEM to reveal the influences of plate thickness on column distortional buckling behaviors. The Direct strength method (DSM) was applied and it was essential to determine column distortional buckling stress before performing DSM to calculate column ultimate strength. A modified calculation method for distortional buckling stress of the irregular-shaped aluminum alloy columns was proposed. Distortional buckling stresses of 81 aluminum alloy columns with different plate thickness were analyzed by the FEM to evaluate the modified calculation method. It was accurate and more efficient to use the modified calculation method to calculate distortional buckling stress of the irregular-shaped aluminum alloy columns in DSM.

Reliability assessment of aluminum alloy columns subjected to axial and eccentric loadings

The reliability and safety of aluminum alloy columns used in China is not well understood. This paper develops an improved probabilistic model for the reliability assessment of axially and eccentrically loaded columns, designed based on the aluminum alloy structure design codes of China. A comprehensive database, including 272 axially and 116 eccentrically loaded columns mainly made of 6061-T6 and 6082-T6 aluminum alloy in China, was established. Using this database, a statistical analysis of test results was conducted to determine the optimal probability distribution which can provide the best fit to the model error (ME) data and the relevant distribution parameters. The statistical parameters of ME, material strength, geometrical properties, load type, and load ratio were considered in the reliability evaluation, and a sensitivity analysis was performed to investigate the effect of these variables on the reliability indices. Then, the structural reliability levels of aluminum alloy columns in compression designed according to Chinese, American, and European codes were compared. By analyzing the optimal probability distribution of ME, the calculation results showed that the safety level of Eurocode 9 was the highest, while that of the American code was the lowest, with the Chinese code being in between. Additionally, the reliability index of 6082-T6 aluminum alloy columns was higher than that of 6061-T6. In view of the analysis results showing that the Chinese code barely met the target reliability index of 3.70, the material partial factor γR was modified for a capacity prediction model of aluminum alloy columns in compression designed according to Chinese code, to ensure that it reached the reliability requirement.

Experimental study and parametric analysis on the stability behavior of 7A04 high-strength aluminum alloy angle columns under axial compression

An experimental program including study has been conducted to investigate buckling behavior of 7A04 high-strength (HS) aluminum alloy columns under axial compression, in which 42 L-shaped extruded specimens were designed and tested. The specimens involved two sections and seven slenderness ratios varying from 15 to 100. The test results were compared with design results in accordance with American Aluminum Design Manual, GB 50429-2007 and Eurocode 9. A finite element (FE) model of the tested specimens under axial compression has been developed by using general finite element software ANSYS, and was verified by using the test results reported herein and other experimental results presented in the literature. By using this FE model, an extensive body of parametric analyses were conducted to clarify the effects of width-to-thickness ratio of angle legs, initial imperfections and material strengths on the buckling resistance of the 7A04 angle columns. Based on the test and FE analyses results, a modified design method was proposed for predicting the buckling resistance of 7A04 high-strength aluminum alloy columns more accurately.

Interacted buckling failure of thin-walled irregular-shaped aluminum alloy column under axial compression

Interacted buckling behaviors and ultimate strength of thin-walled aluminum alloy columns with irregular-shaped cross section were studied using a verified Finite Element Model (FEM). Six interacted buckling failure modes were studied, which were: (1) the interaction of Local bucking and sectional Yielding (LY); (2) the interaction of Local and Global buckling (LG); (3) the interaction of Distortional buckling and sectional Yielding (DY); (4) the interaction of Distortional and Global buckling (DG); (5) the interaction of Local bucking, Distortional bucking and sectional Yielding (LDY or DLY); and (6) the interaction of Local, Distortional and Global buckling (LDG). The load-axial displacement curve, the deflection-axial displacement curve, the development of the axial stress at different positions in the section at mid-span, the out-of-plane displacement at failure along the column length and the axial stress distribution at failure across the section at mid-span were presented. The local buckling and distortional buckling were detected by the turning points on the load-axial displacement curves. The out-of-plane displacement along the column length at failure was used to illustrate the failure mode of the column. Ultimate strengths and failure modes of 174 columns failed by interacted buckling failure modes were investigated by both FEM and current design approaches. For the ultimate strength of the columns under DY failure mode, the results predicted by North American specification for the design of cold-formed steel structural members of American Iron and Steel Institute (AISI) were higher than FEM simulation results. The ultimate strength predicted by American Aluminum Design Manual (AA), Direct Strength Method (DSM), European Code (EN1999) and Chinese Design Specification for Aluminum Alloy Structures (GB50429) were lower than FEM simulation results, no matter what kind of failure modes the column encountered. Mean values of PAA/PFEA, PEC9/PFEA and PGB/PFEA were 0.81, 0.79 and 0.74. DSM could precisely predict the Global buckling (G), LG and DY failure modes. However, for the columns failed by LY, DG, LDY and LDG, they were LG, G, DY and LG when predicted by DSM, respectively. The applicability of DSM to thin-walled aluminum alloy columns with irregular-shaped cross section should be investigated further.

Numerical simulation of aluminum alloy 6082-T6 columns failing by overall buckling

Aluminum alloys have found increasing use in space structures, mainly because of their high strength-to-weight ratio and satisfactory corrosion resistance. The work presented in this article is focused on finite element simulation of the failure behavior of aluminum alloy members subjected to an axial compression load and failing in overall buckling mode. The column members were fabricated by extrusion using the relatively new heat-treated aluminum alloy 6082-T6. An accurate finite element model has been developed for the simulation of aluminum alloy columns. The developed finite element model was verified against experimental results and demonstrated that it is capable of accurately predicting the deformed shapes and the ultimate loads of the tested columns. A parametric study was carried out on the stability of aluminum alloy column members failing by overall buckling. A fitting column curve was proposed for aluminum alloy design; it was somewhat more conservative than the column curve from current Chinese code GB50429.

Test and design method for the buckling behaviors of 6082-T6 aluminum alloy columns with box-type and L-type sections under eccentric compression

In this study, a detailed experimental investigation of 29 extruded columns with box-type and L-type sections made of 6082-T6 aluminum alloy, was carried out to study the stability behavior of these columns when subjected to eccentric loads. Finite element (FE) models of all tested columns under eccentric loads were developed using the ABAQUS software package. The precision and utility of these FE models were verified by experimental data. Both the stability bearing capacity and deformation performance were evaluated. Using the proposed FE models, an extensive parametric study was performed to investigate the effects of section dimensions, slenderness ratio, and eccentricity on the stability bearing capacity of the eccentrically loaded columns. The test and parametric study results were compared to the design capacity predictions in the current Eurocode 9 and the Chinese Code for the Design of Aluminum Structures, GB 50429. It was found that the predicted stability bearing capacities in the two design codes was generally conservative for the eccentrically loaded columns made of 6082-T6 aluminum alloy. Several parameters of the design formulae from the Chinese Code were modified to predict the ultimate strength of 6082-T6 aluminum alloy columns more accurately.

Experimental investigation on local buckling behaviors of stiffened closed-section thin-walled aluminum alloy columns under compression

Six aluminum alloy tensile coupon tests were carried out and stress–strain curves obtained from tests were compared with a Ramberg–Osgood model. Comparison showed that the Ramberg–Osgood model can precisely describe stress–strain relationship of 6063-T5 aluminum alloy. Totally, 10 axial compression tests on thin-walled aluminum alloy members with four stiffened closed-section were carried out. Local buckling occurred in all specimens eventually. The axial displacement, lateral deflection, strain development and failure modes of the tested specimens were recorded. A finite element method (FEM) model was presented to simulate local buckling behaviors of the tested columns under axial load. The ultimate strength, strain development and failure modes obtained from FEM agreed well with the test results. Current design codes on aluminum alloy structures, such as the American aluminum design manual (AA), the European code (EC9), Chinese design specifications for aluminum structures (GB50429), the North American Specification for the design of cold-formed steel structural members (AISI) and the direct strength method (DSM), were used to calculate the ultimate strength of the tested columns. Comparison showed that current design codes overestimated the ultimate strength of stiffened closed-section thin-walled aluminum alloy columns under axial compression loads.

Buckling behaviors of section aluminum alloy columns under axial compression

Thin-walled columns with ▪ section are used widely as columns in aluminum alloy framed structures, offering high strength-to-weight ratios and convenience in connection with maintaining walls. In this paper, thin-walled aluminum alloy columns with ▪ section were studied experimentally and numerically to investigate the buckling behavior and to assess the accuracy of current design methods. A finite element model (FEM) was developed and used to perform parametric studies after being verified by tests. Effects of plate thickness on elastic buckling stress was studied using finite strip method (FSM) and to find the potential buckling failure mode at a given length. Tested ultimate strengths were compared with those predicted by the current American, European and Chinese specifications on aluminum alloy structures and the Direct Strength Method (DSM) on thin-walled structures. Following reliability analysis, the design strength predicted by current design specifications were found to be generally conservative, whereas DSM offered more accurate results.

Buckling behaviors of thin-walled aluminum alloy column with irregular-shaped cross section under axial compression in a fire

Failure modes of the thin-walled aluminum alloy column with irregular shaped cross section at ambient temperature and elevated temperatures in a fire were studied using a verified finite element model. The studied failure modes included the sectional yielding, interaction of local buckling and sectional yielding, interaction of local and global buckling, and global buckling. The finite element model was verified by experimental results from the ultimate strength, the failure modes and the failure deformation. Deformation shape along the column failed by different failure modes was presented. Stresses development at the middle span section was greatly affected by the failure modes. Ultimate strengths of a series of aluminum alloy columns with different length, cross section dimension were analyzed by the finite element analysis and current design codes at different temperatures in a fire. The current design codes greatly underestimated the ultimate strength of the thin-walled aluminum alloy column with irregular shaped cross section. Design method provided by EN1999-1-2 can give an accurate prediction of the ultimate strength of a short thin-walled aluminum alloy column with irregular shaped cross section at temperatures lower than 250°C. A modification to the design method in EN1999-1-2 was proposed for predicting the ultimate strength of the aluminum alloy column with length longer than 500mm and at temperatures higher than 250°C. Ultimate strength predicted by the modified equation agreed well with finite element analysis results.