Neil's News

Bridge Busting 1990

11 October 2010

Bridge Busting is the challenge of building a model bridge and loading it up to, and then beyond, the failure point. These events are enormously popular with students because of their dramatic conclusions. They can also be very educational since one can learn a lot about the fundamentals of structures: tension, compression, bending, shear and torsion. The operative word is "can" since not all such events are created equal.

Professor Don Westwood of Carleton University ran an exceptionally good Bridge Busting event each year. All the students from his Structures in Architecture course (77.113) would build a bridge at the end of the term, then the destruction would be broadcast on TV. Two things made this event stand out from its peers. First, glue was against the rules. Banning glue results in structures that bend and twist as loads are applied, not structures that simply shatter when the epoxy fails. Second, the commentary and slow motion analysis is key to unlocking the lessons that each bridge tells. This event isn't just a demolition, it is truly educational.

I was still in high school when Professor Westwood taught his final term at Carleton, but I was lucky enough to be able to take his class. Recently I rescued a 20 year old VHS tape containing all eight hours of the 1990 event. Below are some highlights and lowlights.

0. Introduction by Professor Westwood -- Lays out the rules and the rationale.
1. Prestressed bridge -- Clean and simple.
2. Kitchen sink bridge -- Many different designs in one.
3. King post bridge -- Student completely fails to understand tension.
4. Single compressive member -- Heavy load with unexpected failure.
5. Minimalist bridge -- Clever use of load as part of structure.
6. Queen post bridge -- Yes, that's me.

I learned a tremendous amount from this course and from participating in Bridge Busting. It opens one's eyes to how the structures which surround us work. Every brace, every bolt, every crack tells a story; it just takes a little bit of knowledge to learn how to read it.

Sadly Professor Westwood is no longer teaching and the university apparently doesn't keep archives of the lectures they taped. Much of the material was also presented in the TVO series "The Science of Architecture" which he hosted, but TVO aren't responding to purchase requests for this series. At its height, his lectures were distributed in thirty countries. But now his life's work has been reduced to a handful of YouTube clips and some fading memories. This is not acceptable.

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