Bridge project

Ellie got an assignment to build a bridge for science this week. It had to span 12”, have a deck 3” wide, and had to be a minimum of 5” about “ground”. And it had to be made from materials found at home. 

Of course I gave Ellie some resources and set her loose to plan. She came back wanting a cable-stay bridge similar to the Zakim. She set to design and gathered materials. Some trial and error later and she asked for my help.

I explained that cable stay bridges are expensive and difficult to construct in the real world. She asked me what the easiest was and I told her a simple box-beam bridge was the CalTrans standard for everyday overpasses. She asked to see one, I showed her one that I’m working on as well as some other images. She said, I can do that with toilet paper rolls...yep! 

And with a CalTrans budget (recycled materials) and an iDOT schedule (short window for construction) she had created an segmented precast box girder bridge that met the project requirements. 

Efficient design. Completed ahead of schedule. Of course, it hasn’t been fully load tested (but that design criteria wasn’t in the project specifications), however, I’m sure it’ll be fine.