National Engineers' Week Student Competitions

UAA Campus, Anchorage, AK

Saturday February 26, 2011; 10:00 am - 2:30 pm
Awards Ceremony at 3:00 PM

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Structural Engineering: Bridge Competition Rules

Last edited 1/26/2011


Location:  Trimble MTS Laboratory, Engineering Building

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:

  1. 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.

  2. 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.

  3. Height: No limit except as noted above for width.

  4. 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.

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

  6. 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.

  7. 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.

Testing & Scoring:

Bridges will be tested using the MTS machine located in the Engineering Building basement. The bridge will be secured between two points while a muffler clamp is placed in the middle of the bridge. The MTS will pull downward on the bridge and measure the amount of force, or loading, that the bridge can withstand until it breaks. Scoring for the bridge competition will be accomplished using the following equation:

    (Bridge Load at Failure) / (Bridge Mass)

Bridge mass will be calculated as noted under the Mass specification above.

Highest ratio of load to mass wins!!!