Keywords: aluminium, buckling of shells, Eurocode 9, finite elements, shell analysis, shell design.

The design of aluminium thin shells subject to axial compression has been widely investigated and the amount and complexity of the data can engulf the design engineer. Eurocode 9 has simplified the design approach to aluminium shells by having a set of factored design considerations that satisfy thin shell theory. However Eurocode 9 does not state that the methods are inappropriate for hand calculations and that numerical finite element analysis must almost always be used. A commentary on the best use of each type of analysis would help a design engineer to select the method best suited to a particular application.

This research evaluated the analysis methods in Eurocode 9 to generate a number of criteria to aid engineers in selecting an appropriate analysis method for their specific application.

The risk posed to thin shell aluminium structures subjected to buckling forces is well considered in Eurocode 9 through the application of safety factors which make it necessary to reduce the material capacity of the thin shells by an additional 10% of the material proof strength. This reduction is to account for imperfections and load eccentricities in any plasticity based analysis other than the geometrically and materially non-linear analysis with imperfections analysis (GMNIA). Equally, stress based design alternatives are presented that allowed the calculation of comparable results from less resource demanding analyses. In this research only the option for membrane theory analysis (MTA) has been fully assessed, but revealed a high level of accuracy when compared with GMNIA. It is clear that caution is needed when selecting an appropriate analysis method. From hand calculations and linear elastic bifurcation analysis (LBA), the critical buckling mode was overestimated and could lead to unconservative assumptions concerning the capacity of the structure. Exposure to this risk is dealt with by Eurocode 9 through the use of limit load factors or equivalent design stresses. The necessity to apply these factors or how to do it is not self explanatory and needs to readdressed in clearer language. Clarification of design progression through Eurocode 9 would be helpful to new users. A design progression is suggested by the authors.

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