Civil Engineering

Last weekend I helped out at the 33rd Annual International Bridge Building Competition. It was held at a local high school, and our local Physics Teachers’ Association had helped to sponsor it. Students came from all over the country, having qualified in a regional competition earlier in the year.

While the Illinois Institute of Technology sponsors the competition, they try to hold the final event at a different location every other year, in between holding it in Chicago. This year our local Physics Olympics League had bid to host, and we won!

The goal of the competition was to build the most efficient bridge, materials-wise. Everyone had to use official competition basswood (which was specially dyed with a fluorescing dye detectable with UV light) and had to keep their bridge below 30 grams in mass. The bridges had to span a gap of 30 cm, and there were restrictions on height and the level of the “road” and there were requirements for the places where the load mass could be placed. Then each bridge was individually loaded from below with sand poured into a bucket until the bridge gave way. The bridge that supported the greatest mass of sand per gram of bridge mass would win.

The bridges were assigned a random order for testing, and as each student set up their bridge and started pouring sand the audience hushed.  The longer the time before breaking, the more sand and the more mass.  And the quieter the crowd.  Each crack of breaking bridge released a sigh and applause.  Then the mass of the sand was entered into a computer and the efficiency displayed on the screen above the stage.  The spreadsheet with the data was set up to display the rank of each bridge from most efficient to least, and the student with the number one bridge had to watch all the bridges after hers, hoping that none of them would be more efficient and displace her top score.

This is the winning design for this year:

The girl who made this bridge went home with an iPad and an offer of $15,000 per year for four years in scholarship money if she is accepted at the Illinois Institute of Technology!

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