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

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

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

Prototype Testing Component Analysis

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

Prototype Testing Prototype Analysis

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

Arch with String Support Designs Solid Arch Arch with String Support Truss Arch

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

Final Design

Prototype Performance Prototype Testing Prototype Performance

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

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

Final Design

Design Sheet

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

Failure Points

Conclusion

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.

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.