Behaviour and Design of Aluminum Alloy Structural Members

Book excerpt: This dissertation, "Behaviour and Design of Aluminum Alloy Structural Members" by Jihua, Zhu, 朱繼華, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled BEHAVIOUR AND DESIGN OF ALUMINIUM ALLOY STRUCTURAL MEMBERS Submitted by ZHU JIHUA for the Degree of Doctor of Philosophy at The University of Hong Kong in September 2006 The behaviour and design of aluminum alloy structural members are investigated in this study. The research focused on aluminum columns, beams, and beam-columns of square, rectangular and circular hollow sections. Both experimental and numerical investigations were performed and reported. The effects of transverse welds on column strengths were also investigated. Design rules for aluminum columns with and without transverse welds were proposed. The experimental study included column, beam and beam-column tests. The test specimens were fabricated by extrusion using normal strength aluminum alloy 6063- T5 and high strength aluminum alloy 6061-T6. Both the non-welded and welded material properties were obtained from different coupon tests. The local and overall geometric imperfections were measured. The test program for fixed-ended columns was conducted on 70 column specimens that included 50 columns with both ends welded to aluminum end plates and 20 columns without welding of end plates. The column length ranged from 300 to 3000 mm in order to obtain a column curve for each test series. The test program for beams and beam-columns included 6 pure bending tests and 44 beam-column tests of five different cross-sections. Pure bending tests were conducted for each test series to determine the bending capacities of the specimens. The beam-column specimens were compressed between pinned ends at different eccentricities in order to obtain an interaction curve for each series of test. The test strengths were compared with the design strengths calculated using the American, Australian/New Zealand and European specifications for aluminum structures. A numerical investigation of fixed-ended aluminum alloy tubular columns of square, rectangular and circular hollow sections is also presented. An accurate finite element model was developed. The initial local and overall geometric imperfections were incorporated in the model. The non-welded and welded material nonlinearities were considered in the analysis. The welded columns were modeled by dividing the columns into different portions along the column length, so that the heat-affected zone softening at both ends of the welded columns was included in the simulation. The nonlinear finite element model was verified against the experimental results. It is shown that the calibrated model provided accurate predictions of the experimental loads and failure modes of the tested columns. Hence, the model was used for an extensive parametric study of cross-section geometry. The parametric study included 248 column specimens that covered a wide range of column length and cross-section dimensions. The heat-affected zone softening factors have been proposed for square and circular hollow sections based on the results obtained from the parametric study. Design approaches for aluminum alloy tubular columns with and without transverse welds were proposed. Column strengths predicted by the finite element analysis were compared with the design strengths calculated using the current American, Australian/New Zealand and European specifications for aluminum structures. In addition, the direct strength method, which was originally developed fo