Here is a video:

The idea behind this bridge was to create an aesthetically pleasing bridge, while still keeping it simple to build. I wanted a really basic arch bridge design in order to compare it to a simple beam bridge that I also built. You can purchase plans for this bridge in my store.

You can see from the video that this bridge collapsed from the middle. I think that if the ends of the bridge had been braced like a real life arch bridge, this bridge would have held considerable more weight before it broke. But as a free standing arch bridge made from popsicle sticks, I think it was pretty good.

I found pictures of some old trusses I built for Science Olympiad bridges. Most of these were built in the 2003-2004 school year. I thought I would post them to give examples of how these trusses could be used in model bridges.

This bridge building kit from Amazon actually has three different bridges. It comes with all the supplies you need to build a suspension bridge, a truss bridge, and an arch bridge. All of these combined make this kit an excellent gift idea, or something you can build just for fun. The package also contains an informational booklet which talks a lot about how bridges work, and is really quite good. I remember referring to this booklet time and again when trying to figure out the different forces that act on bridges.

If you are looking for a good bridge building project, this could be perfect. The kit is not expensive, and contains a lot for the price. I definitely recommend this kit. The Kit is called “Our Amazing Bridges Architecture Kit” and can be purchased at Amazon.com here.

It is pretty easy to see how this bridge failed: the bottom fell out. This is a fairly easy fix, and might have been due simply to poor wood selection. Had I paid more attention to the quality of wood I was using, this failure might have been avoided.

I used two pieces for the arch. I had a square 1/16″ x 1/16″ piece of Basswood for the bottom of the arch. Then I glued a rectangle piece of Balsa wood on top of that to form a T beam. This method worked pretty well, but Balsa is harder to bend than Basswood.

I just completed a new toothpick bridge that’s quite different than my last one. It’s an arch made from curved trusses, formed once again with toothpicks and wood glue. This one won’t be tested either (sorry!) because it was made for a friend who creates custom action figure dioramas. But I designed the bridge to have the highest ratio of maximum load to bridge weight and some ad hoc tests made me pretty optimistic.

The bridge is 24 inches long, 4.5 inches wide and 2.75 inches tall at the top of the arch.

I feel like I cheated a bit because I used split bamboo skewers to connect the two curved trusses. I wasn’t really following any rules, but if I had more time I would have liked to do all of the crossbars and supports out of toothpicks. There are more pictures from different angles on my photostream, at http://www.flickr.com/photos/razokylava/