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Model Project Test Results
Conclusions

Arch 324, Introduction to Structural Design, University of Virginia
Last updated Tuesday, March 12 1996, at 5:14 PM Copyright © 1996, Kirk Martini

Conclusions

It would be easy, but not quite right, to conclude from these results that beams are stronger than arches, since most of the strongest structures were beams. A more appropriate conclusion is that stability is extremely important: you cannot take full advantage of the material's strength (and these materials are very strong at this scale) unless you prevent stability failure. Within the constraints of this particular problem, structures with a depth greater than 6 to 8 inches tended to suffer stability problems at relatively low loads, while shallow and wide structures were able to defer stability problems until much higher load levels.

Stability failures are strongly three dimensional. When we analyze structures in two dimensions, we assume that there is bracing to prevent movement out of the 2D plane. In theoretical models, assumptions are enough. In real structures, they are not; the lateral bracing has to be there. As the case studies in Petroski make clear, design failures most commonly arise by forgetting to consider something, rather then considering it incorrectly.

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Last updated Tuesday, March 12 1996, at 5:14 PM
Copyright © 1996, Kirk Martini
Please send comments or questions to Martini@virginia.edu
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