National Engineers' Week Student Competitions

UAA Campus, Anchorage, AK

Saturday February 24, 2001; 10:00 am - 2:00 pm

Structural Engineering Competition:

Location: UAA Engineering Building Atrium & Materials Lab

Objective

Design and build a bridge using only balsa wood and glue which will support the greatest weight while meeting the required specifications. The winning bridge will be the one that has the highest strength to weight ratio (i.e., the maximum load held divided by the weight of the bridge).

Specifications

Length: The bridge must span an opening that is 60cm (+ 0.5cm) wide. Allow for some overlap onto the test stand. The vertical face of the supports may not be used to provide support for the bridge (i.e., bridges depending on horizontal support from the test set up will be disqualified).   The overall length of the bridge cannot exceed 76 cm.  Bridges longer than 76 cm will not fit on the load frame.

Width: A commercial 2x2 (actual dimensions are approximately 1.5"x1.5") must be able to pass through the length of the bridge without obstruction.

Height: No limit except as noted above for width.

Shape: Any shape can be submitted, as long as it meets the length, width, and height requirements. It does not have to look like a bridge.

Mass: Bridges should be at or below 50 grams. Bridges more than 50 grams will be penalized by considered the bridge to weigh 50 grams + (actual weight-50 grams)^1.5.

Materials: Wood is to be any commercially available BALSA wood.

Glue is to be any commercially available glue. Hardened glue by itself may not be used as a structural member.

Loading: A standard 2.5" muffler clamp (3/8" diameter, 3.1/8" + 1/8" C-C of legs) with a pair of 5 cm square plates (see images) will be attached at the center of the span at the elevation of the test stand (+ 2.5 cm). The bridge MUST accommodate this loading apparatus, so be sure to include it in your design.

Some information on Balsa wood can be found at:  http://www.zimsweb.com/balsa/