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Bridge Contest Rules

1. Materials - Balsa wood and carpenter's glue are the only two materials which may be used to build the model. No other materials or coatings are permitted.

 

 
 
 

2. Bridge System

 

 
 
 

1. The model must be able to span between two supports placed 24" apart. The supports provide only (upward) vertical forces.

 

 



 The model length should be between 24 1/2" and 26".
 
 

2. The height of the model must be less than or equal to 8". The weight of the model must be less than or equal to 5N.

 

 
 
 

3. The width of the model must be less than or equal to 12".

 

 
 
 

4. The model must have a horizontal deck along its entire length. There must be a minimum 4" x 5" open area above the deck along its entire length.

 

 


 
 

5. The model will be tested by applying a downward force on the horizontal deck over a 2" x 4" area. The load will be applied at one of three possible positions: 
1. 
2. 
3. 
The load position will be determined on the day of the contest. All entries will be loaded at the same position. 
3. The following quantities will be measured:

 

 
 
 

1. The vertical deflection of the bridge at the loading position.

 

 
 
 

2. The applied force
The test will be stopped when the applied force reaches a maximum and then begins to decrease or when the deflection reaches a value of 2".
 
 
4. Performance

 

 

 Three quantities will be used to evaluate performance: 

1. Maximum applied force/(model weight) 
2. (one-fifth of the maximum applied force/corresponding vertical deflection)/(model weight) 
3. Innovativeness-aesthetics of design 
5. Awards

 

 

 All student participants will receive a commemorative T-shirt. Teams are limited to one or two members.

 A $75.00 prize will be awarded for the entry with the largest: (maximum applied force)/(model weight)

 A $75.00 prize will be awarded for the entry with the largest: (one-half of the maximum applied force/corresponding vertical deflection)/(model weight)

 A $75.00 prize will be awarded for the entry which is judged to be most innovative and has the best appearance.
 
 

6. An entry must meet all the rules in order to be eligible. All entries will be judged for eligibility. Judges' decisions are final.

 

 
 
 

Hints and Suggestions

1. Some readable reference texts are:

 

 
 
 

1. Gordon, J.E. "Structures or Why Things Don't Fall Down," Plenum Press, 1978. 
2. Salvadori, M. and Heller, "Structure in Architecture". 
3. Meriam, J.L. "Engineering Mechanics, Vol. I - Statics," J. Wiley. 
2. A solid rectangular block of wood will not be the most efficient solution (and is not in the spirit of the contest).

 

 
 
 

3. Failure can occur from "lateral instability" if the model is tall and narrow.

 

 
 
 

4. The area over which the force is applied can "punch through" the deck. So strengthen the deck under the loading area.

 

 
 
 

5. Some possible systems which you can consider:

 

 
 
 

1. A "box beam"

 

 
 
 

2. A "tied" or "bowstring" arch

 

 
 
 

3. An inverted "tied" or "bowstring" arch

 

 
 
 

4. A "deck" truss (a triantulated network of pieces)

 

 
 
 

5. A "through" truss

 

 
 
 

6. A "king post" "through" truss

 

 
 
 

7. An inverted "king post" truss

 

 
 
 

8. A "girder" or beam bridge