1. Elevated Bridge

2. Elevated Bridge Instructor
Andrew Roberts
7 year participant in Science Olympiad
Multi event medal winner in regional and State competitions
Coached State Champions in Wright Stuff.
4 year SO Summer Camp Instructor.
Science Olympiad Student Intern

3. Process Read and understand the rules Research Brainstorm Design Build
Supplies & Tools
Test
Analyze…Repeat last 4 steps

4. Rules
Make several copies of the rules and always have one with you while working
Identify important measurements
Measure your drawing as you design to be sure you meet the rules.

5. Rules Efficiency is actually all that matters. Efficiency =
A 30g structure holding 15kg(15,000g) has an efficiency of 500
Mass Held
Bridge Mass

6. Test Board Setup

7. Division B Testing Board

8. Division C Testing Board

9. Important Measurements (B)
Must span cm
Must clear 15x15 cm in center
Max height of 20cm

10. Important Measurements (C)
Must span cm
Must clear 30x12.5 cm in center
Max height of 20cm

11. Other Important Rules Can only touch the testing board in Bearing Zone
There is no maximum wood size.
Must support 5x5x2cm block on top mid span
Must be wood (no bamboo or commercial laminates)

12. Research / Bibliography
West Point Bridge Design

13. Brainstorm Take a field trip and look Bridges
Ask students to draw what they liked
Discuss sketches
Make sure they understand the device that holds the most weight does not necessarily win.

14. Supplies/Tools Copy of the Rules Drawing Board Paper/drafting Pencils
Eraser
Metal ruler
T-square
Testing equipment
Balsa
Razors
Saw
Glue
Accelerator
Packaging Tape
Building Board
Acetone
Sanding block
Level

15. Balsa Has the highest strength to weight ratio of all woods
Has a greater tensile strength than compression strength
Is easy to shape and work with
It is cheap

16. Balsa

17. Adhesives Wood Glue Green Tube Glue () Super Glue/CA glue Accelerator
Mix with rubbing alcohol 1part to 1part
Green Tube Glue ()
Super Glue/CA glue
Accelerator
Glue can be a major weight factor, but it doesn’t have to be. You can easily use 1-2 grams of glue (or less) on a 10-gram bridge.

18. Design Everything must be square, level, and symmetric.
Draw your plan on paper and tape it to a rigid, flat surface.
Cover the plans in a non stick surface. Clear packaging tape works best.

19. Tensile Advantages
The tensile strength of balsa is much greater than its compression strength(19.9MPa compared to 12MPa)
This means you can use a smaller piece to hold the same weight if that member is in tension.

20. Construction Build two sides and then connect them to each other.
You can hold pieces down with scotch tape or by crossing T-pins over them (don’t put pins through the wood).
If pins are used, keep pins away from glue joints.

21. Joints
Lap Joint:
The lap joint is one of the strongest, and you should use it whenever you can. It strengthens compression members because it adds stiffness. The lap joint has one drawback, however. The joint is only as strong as the face of the wood.

22. Joints
End Joint:
The end joint is not a very strong joint, especially for tension members. In tension, the two pieces of wood will just pull right away from each other.

23. Joints
Notched Joint:
The notched joint gives more strength than the end joint, but less than the lap joint. It is more difficult to build, so it is not very common.

24. Joints
Gussets:
If you have to use an end joint, it is a good idea to add a gusset to make it stronger. The gusset creates a lap joint, which is strong in both tension and compression.

25. Joints On your X braces, they must be connected in the middle.
Glue here!

26. Trusses
Warren Truss

27. Trusses
Pratt

28. Trusses
Howe

29. Trusses
K Truss

30. Ideas

31. Ideas

32. Ideas

33. Ideas

34. Ideas