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From:
http://www.lusas.com/case/civil/spitfires.html
Text from the website:
"'The Sentinel' is an award winning 16m high sculpture in Birmingham, UK, consisting of 3 half-scale aluminium Spitfires peeling-off in different directions and supported by curving steel "]'vapour trails'. It captures the dynamics of the Spitfire in flight and commemorates the nearby Castle Bromwich factory, which now produces Jaguar cars, where most of Britain's wartime Spitfires were built. Maunsell was appointed to design the sculpture and used LUSAS Civil & Structural analysis software to optimise member sizes and help turn the artist Tim Tolkein's vision into reality."
Buckling
"With a satisfactory natural frequency determined, the wind loads could be calculated and the structural analysis could continue. As design codes do not exist for such a structure, the sculpture had to be designed from first principles. The buckling analysis included calculation of the local stresses in the steelwork and calculation of the dynamic buckling effects."
"An eigenvalue buckling analysis was used to determine the buckling capacity due to self weight and applied wind loads. The graphical output from LUSAS Civil & Structural allowed easy viewing of the mode of failure and any weaknesses to be examined. In early analyses, the structure's first buckling mode occurred in the sub frames. These sub frames hold each cluster of trails together and support the aluminium plane silhouettes. A value of >2.5 was selected for the target load factor for buckling. However these first attempts provided a value less than 1.0, so the section size of the sub frame was increased and the buckling modes were transferred to the trails. The thickness of the base sections of the trails was increased and more trails were interconnected. These strengthening measures increased the lowest load factor for buckling to above 3.5 with a corresponding natural frequency of 1.34."
LUSAS is a trademark and trading name of Finite Element Analysis Ltd.
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