Engr100: Prototype Bridge Testing Result

All groups have been designing and building their prototype bridges for four days and now it's time to test and break it. During this test we are going to find out which part (structure and location) inside the bridge is easy to fail, why it fails and what we can do to modify our final version.

Basically, structure (bridge) failure can be defined as several following types:

1. Bending (endure bending moment) / Buckling (endure compressive load);

2. Twisting (endure torsion) / Rotating;

3. Yielding (endure tensile load - only for ductile material);

4. Cracking (endure comprehensive load);

Why structure fails?

A structure will fail if there is a concentrate load acting on it and over the endure limit. For example, this is just like how we break a piece of wood, when we start to bend it, the largest bending moment will always appear in the middle, that's why breaking line always happens around center part (assume cross section area and material behavior is equal throughout the bar).

Testing Results:

Group 1:

Team Members: Spencer, Austin, Daniel, Phillip, Carina, Mikk

Bridge Net Weight: 393.00 grams

Max Compressive Load: 1102.93 lb

Compressive extension at Maximum Comp. load: 11.75 mm

Load Per Unit Weight (Index): 1275.65

Rank: 1

Group 2:

Team Members: Sundona, Derek, Philip, Jeff, David

Bridge Net Weight: 395.00 grams

Max Compressive Load: 300.38 lb

Compressive extension at Maximum Comp. load: 17.34 mm

Load Per Unit Weight (Index): 345.66

Rank: 5

Group 3:

Team Members: Amanda, James, Brandon, Michael, Kris

Bridge Net Weight: 244.00 grams

Max Compressive Load: 581.52 lb

Compressive extension at Maximum Comp. load: 14.56 mm

Load Per Unit Weight (Index): 1083.31

Rank: 2

Group 4:

Team Members: Calder, Jared, Jonathan, Mike

Bridge Net Weight: 182.00 grams

Max Compressive Load: 89.66 lb

Compressive extension at Maximum Comp. load: 12.02 mm

Load Per Unit Weight (Index): 223.93

Rank: 7

Group 5:

Team Members: Jimmy, Ariel, John, Justin

Bridge Net Weight: 239.00 grams

Max Compressive Load: 106.76 lb

Compressive extension at Maximum Comp. load: 8.97 mm

Load Per Unit Weight (Index): 203.04

Rank: 8

Group 6:

Team Members: Katie, Paul, Cyrus, Jordan, Chun

Bridge Net Weight: 208.00 grams

Max Compressive Load: 311.68 lb

Compressive extension at Maximum Comp. load: 4.83 mm

Load Per Unit Weight (Index): 681.12

Rank: 3

Group 7:

Team Members: Travis, Sarah, Erin, Tyler

Bridge Net Weight: 179.00 grams

Max Compressive Load: 110.29 lb

Compressive extension at Maximum Comp. load: 11.49 mm

Load Per Unit Weight (Index): 280.06

Rank: 6

Group 8:

Team Members: Jae, Bernadette, Matt, Victor

Bridge Net Weight: 290.00 grams

Max Compressive Load: 346.69 lb

Compressive extension at Maximum Comp. load: 14.50 mm

Load Per Unit Weight (Index): 543.40

Rank: 4

How can we modify the prototype bridge?

Generally, well understanding to statics is the key. Try to do some self-study on examples about force/moment balance and analysis. For specific problems from each group please refer to those suggestions above.