Most students started out with a flat plank style bridge. since then and a little bit of looking at pictures most students have started incorporating triangles into their designs, which is a really smart move. I hope you have the research to explain why that's such a smart move in your papers.
I'm really excited about all the different designs I'm seeing the kids come up with. We need to increase the pace that we are crafting with so that we can test them all and have many iterations. it is concerning that 2 weeks in and most groups are still on their second or at best third iteration. speed of crafting instead of making sure each iteration is completely perfect is a challenge for the class.
We have also started a reddit community at http://www.reddit.com/r/warreninnovation/ where students are sharing design models and useful research sites. i hope to see more upvoting and comments soon but i have noticed a small but steady increase in the number of students using the site as a resource.
and now for the glimpse of your next challenge. just to tantalize a little bit. it will involve rat traps (like mouse traps but bigger) and i will be removing material restrictions!