Abstract

This paper presents an experimental investigation of aluminum alloy circular hollow sections subjected to pure axial compression between fixed ends. The specimens were fabricated using 6063-T5 and 6061-T6 heat-treated aluminum alloy. The test program included 29 column tests which were separated into 4 test series of different type of aluminum alloy and cross-section geometry. Each test series contained at least 5 columns with both ends transversely welded to aluminum end plates using the Tungsten Inert Gas welding method, and 2 columns without welding of end plates. Hence, the effects of welding on aluminum alloy columns could be investigated. The specimen length ranged from 300 to 3000 mm in order to obtain a column curve for each test series. The observed failure modes for the column tests include yielding, overall buckling, and material yielding in the heat-affected zone. The test strengths were compared with the design strengths predicted by the American, Australian/New Zealand and European specifications for aluminum structures. The purpose of this paper is to present the test results of aluminum alloy circular hollow section columns with and without transverse welds, and to check the accuracy of the design rules in the current specifications.

Keywords: Aluminum alloys; Buckling; Column; Experimental investigation; Heat-affected zone; Structural design; Transverse welds

Nomenclature

A

gross area;

COV

coefficient of variation;

D

overall diameter of CHS;

E₀

initial Young’s modulus;

coefficient for compression members in the AS/NZS Standard;

L

length of specimen;

effective length of specimen;

n

exponent in the Ramberg–Osgood expression;

unfactored design strength of non-welded column calculated using material properties obtained from tensile coupon tests for American Aluminum Design Manual;

unfactored design strength of welded column calculated using material properties obtained from tensile coupon tests of 25 mm gauge length for American Aluminum Design Manual;

unfactored design strength of non-welded column calculated using material properties obtained from tensile coupon tests for Australian/New Zealand Standard;

unfactored design strength of welded column calculated using material properties obtained from tensile coupon tests of 25 mm gauge length for Australian/New Zealand Standard;

unfactored design strength of non-welded column for Eurocode 9;

unfactored design strength of welded column calculated using non-welded material properties for Eurocode 9;

experimental ultimate load of column (test strength);

mean value of tested-to-predicted load ratio;

r_y

radius of gyration for the CHS section;

t

thickness of section;

δ_x

measured column overall geometric imperfections about x-axis at mid-length;

δ_y

measured column overall geometric imperfections about y-axis at mid-length;

elongation (tensile strain) at fracture;

local buckling coefficient specified in the Eurocode 9;

heat-affected zone (HAZ) softening factor specified in the Eurocode 9;

σ_0.2

static 0.2% proof stress; and

static ultimate tensile strength.

Article Outline

Nomenclature

1. Introduction

2. Experimental investigation

2.1. Test specimens

2.2. Material properties

2.3. Ramberg–Osgood expression

2.4. Column tests

2.5. Measured overall geometric imperfections

2.6. Test results

3. Design rules and design column curves

4. Comparison of test strengths with design strengths

5. Conclusions

Acknowledgements

References