cans’n’spans

The structures portion of our SCI-TECH sequence is super hands-on, and has become sort of a trademark of the program. While we do cover theory and calculations for basic structural elements, we’ve always felt that building things, testing them, and talking about how real structures are behaving under load is the best way to instill the sort of intuitive understanding of statics and structural form that architects really need when they sit across the table from actual engineers. Rob Whitehead’s structures labs are famous for their large-scale tests, using twenty or fifty pound bags of sand and with everything but walkup music as students turn out to watch big things get broken.

So, how do you get the same haptic learning accomplished in a pandemic? Working with rock star colleague Eric Badding and teaching assistant Anannya Das, we took our long span structures module entirely online this term. Last year we organized it to provide an experimental pathway toward designing a studio-scaled long span–four feet of span, carrying fifteen pounds of load–and asked them to first sketch out ideas, then to build scale models and prototypes before the final test. This year, we scaled it down to kitchen table-size, and asked students to work remotely or in limited numbers in the College’s studios. We restricted materials to just chipboard and hot glue to make it easy to source, and the department funded small jewelers’ scales for groups of two or three students, and we asked them to develop and test structures spanning just 24″ and carrying 16-ounce cans of beans. As a serviceability test, we asked them to roll another can of beans under the span during loading–and the lightest structure to pass that test would earn an automatic 100% for the module.

For the scaled down models, students submitted videos of their tests and .pdfs of sketches or descriptions. But for the final competition yesterday, we got everyone on zoom and asked them to test their models live. Each team had a three minute slot, and we set up a Google Doc so that teams could see when their turn came around so they could be ready to dive right in.

Happy to say that the results were convincing–thanks to good coaching and a diligent timekeeper we saw about 30 long spans carry their cans of beans, and ended up awarding joint first place to projects that did it with 36 and 54 grams of cardboard, respectively–about a 20:1 load/weight ratio. Many of the entries adopted fairly pure structural forms, figured out the secondary and tertiary modes of failure like racking or torsion, and applied the notion of ‘hacking’ shapes to remove dead weight where it did the least amount of work–all themes we tried to emphasize in the long span unit.

And, many of the teams turned out genuinely good looking work–signs that even under the most dire of circumstances good design wins out.

4 thoughts on “cans’n’spans

    • YES–absolutely right, and we spent this group’s three minutes talking about foundations and horizontal thrusts…decided that carpet was a “productive cheat” b/c it exemplified an important principle…will outlaw carpet in future competitions!

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  1. Just wondering, if one were able to do those sort of things, could you model one of those in structural design software and do any predictive study? Or even post-study as opposed to the trial and error hacking. It might not be as fun as the test to failure with cans, and it is not a skill I have, but it would be cool

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    • Yes, definitely–but we’ve intentionally stayed away from digital simulation, since it involves a real investment of time and the ‘haptic’ nature of building, testing, seeing how things fail IRL has some real pedagogical benefits. If we had the time to teach the software, of course, it would be great to do both…left brain, right brain…

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