1. Bridge Project: Team Truss-Arch
By Laila Dingwall, Casey Byers, Katie Glore, and Kyle Fowler

2. Outline Introduction Prototype Final Design Evaluation and Conclusion
Construction
Testing
Final Design
Evaluation and Conclusion

3. Goals
Efficient
Meet Constraints
8in
19in
2.5in
16in

4. Prototype Testing
Component Analysis

5. Component: Compression
Keep depressors short for more strength
Longer members fail under less weight
Make sure to pick stronger depressors from box when selecting

6. Prototype Testing
Prototype Analysis

7. Research
The design of the arch of the Fremont Bridge (Portland, OR) inspired the design of the top and bottom arches
From various truss structures it was noticed that all utilize triangles.
This knowledge helped in the connecting of the arches together
Construction of the Fremont Bridge, 1973
Above photo courtesy of the Office of Auditor, City of Portland

8. Arch with String Support
Designs
Solid Arch
Arch with String Support
Truss Arch

9. Design Pros and Cons Design Strengths Weaknesses Solid Arch Strong
Stable
Solid
Heavy
Limited Supplies
No Room for Internal Structure
Weak Points at Glued Joints
Arch with String Support
Strongest (looking)
Counteracting Forces
Triangle Shape
Long Pieces
Complex
Weak Pints at Bottom
Truss-Arch
Lightest
Stable with 2 Arches
Room for Internal Structure
Fewer Supplies Needed
Not as Strong as Others
Lots of Joints

10. Final Design

11. Prototype Performance
Prototype Testing
Prototype Performance

12. Testing Process Prototype Weight: 0.712 lbs Anticipated Load: 100 lbs
Prototype Maximum Load: 165 lbs
Prototype Efficiency: 232

13. Why the Prototype Failed
Notice how the bridge is not squarely on the jig
This caused it to slip off

14. Final Design

15. Design
Sheet

17. VS Prototype Final Weight .712 lbs .62 lbs Max Load 165 lbs 341 lbs
Efficiency
232
550
137% Increase

18. Failure
Points

19. Conclusion

20. Conclusion
Arch bridge used to distribute the weight to the ends of bridge and to the jig.
Diamonds were used on the top of bridge was used to push pressure to the arches.
Internal X structure used to keep it from collapsing at the point of pressure.
Precise measurements were made to see that the bridge was built to fit perfectly into the jig.

21. Conclusion
Bridge failed both times on the ends and started to buckle at the diagonal connectors.
Shorter sticks could have been used for the connectors.
Glue other then the hot glue could have been used for joint strength. (Time was the reason for initial use.)
More reinforcements to keep the arches from bending.