Bridge Project: Team Truss-Arch

By Laila Dingwall, Casey Byers, Katie Glore, and Kyle Fowler

Outline

• Introduction• Prototype

– Construction– Testing

• Final Design– Construction– Testing

• Evaluation and Conclusion

Goals

– Efficient – Meet Constraints

8in

16in

19in

2.5in

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

Above photo courtesy of the Office of Auditor,

City of Portland

Construction of the Fremont Bridge, 1973

Designs

Solid Arch

Arch with String SupportTruss Arch

Design Pros and ConsDesign 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

•Heavy •Long Pieces •Complex •No Room for Internal Structure •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 Testing

Prototype Performance

Testing ProcessPrototype 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

FailurePoints

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.