Bridging A Gap: Balsa Wood Bridge

Posted: October 16, 2005 in my news

This was one of the best assignment I’ve ever got… and the testing even though rather sad was the best part… For Introduction To Civil Engineering, we were given an assignment to build a bridge for a span of 750mm. We were given 3 planks of balsa wood (the softest wood on earth… or at least I think so…) 1 is 3mm thick and 2 were 1.5 mm thick, as well as 3 pieces of bearing plates (harder pieces for carrying load), and a stick of glue… The bridge was then to be tested to see how strong it was… We worked in groups of 4… My group chose to build a simple truss bridge with rectangular hollow supports which carry the load to the sides… Here what it looked like…

The last picture shows how it failed… basically it’s a local failure… which means the angles of our support weren’t big enough and the joint at the top wasn’t strong enough and buckled under the pressure… as you was see the supports are still very much intact and undisturbed… a shame… we put so much effort into it… that was the sad part… My group’s bridge was able to stand 60lb/27.2kg… not too bad… The overall performance of task gave a lowest of 10/4.5 and highest was 90/40.8 and it was still undamaged… Here are most of the bridges from the task with their maximum strength (++ means they are still undamaged)…

Beams-Box Girders




Beam-Box Girder/Truss Combinations





Arch/Truss Combinations



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