Have fun, build a bridge
A good friend recently started teaching at Portland State University. One class she's teaching has a segment on bridge building, and it sounds fun. Luckily anyone can have fun too, by downloading West Point Bridge Designer, free award-winning software that lets you design a bridge, load test it. There is an annual contest associated with it, and this year's content starts January 3rd. The goal is to build the minimum cost bridge that will pass the load test. I've been having a blast designing bridges and trying different techniques to minimize the cost.
I tried to start building a bridge without using a template, and it turns out to be harder than you might think. (Well, engineers might know its hard.) After about two hours of collapsing bridges, I gave up and decided to use a template. Once I had done a few templates, then I was able to try a few free form bridges. My best bridge so far cost only $197K to build. The winning entry last year was a bridge that cost $155K to build.