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: Isaac DeLeon, Kurt Stalsberg, Reyn Fernandez, Fabian Leyva

Bridge Net Weight: 350.00 grams

Max Compressive Load: 531.91 lb

Compressive extension at Maximum Comp. load: 5.78 mm

Load Per Unit Weight (Index): 690.79

Rank: 2

Group 2:

Team Members: Ian Hash, Garrison Burger, Molly Swartz, Andrew Bui

Bridge Net Weight: 190.00 grams

Max Compressive Load: 109.54 lb

Compressive extension at Maximum Comp. load: 2.16 mm

Load Per Unit Weight (Index): 262.05

Rank: 7

Group 3:

Team Members: Andrew Kemis, Brandon Mulligan, Nathan Hirsch, Ryan Sun

Bridge Net Weight: 225.00 grams

Max Compressive Load: 1880.19 lb

Compressive extension at Maximum Comp. load: 6.67 mm

Load Per Unit Weight (Index): 3798.37

Rank: 1

Group 4:

Team Members: Mickey Woo, Jake Antles, Charlie Foster, Vitaliy Zhdanov

Bridge Net Weight: 285.00 grams

Max Compressive Load: 313.21 lb

Compressive extension at Maximum Comp. load: 3.89 mm

Load Per Unit Weight (Index): 499.54

Rank: 4

Group 5:

Team Members: James Kehoe, Tracy Yuan, Hannah Yuen, Vinaykumar Miriyala

Bridge Net Weight: 260.00 grams

Max Compressive Load: 126.57 lb

Compressive extension at Maximum Comp. load: 15.01 mm

Load Per Unit Weight (Index): 221.28

Rank: 8

Group 6:

Team Members: Jeff Lestz, William (Zak) Zabriskie, Michael Murner

Bridge Net Weight: 265.00 grams

Max Compressive Load: 196.21 lb

Compressive extension at Maximum Comp. load: 27.31 mm

Load Per Unit Weight (Index): 336.55

Rank: 6

Group 7:

Team Members: Gabriella Patilea, Ellie Robbins, Shayna Beckman, Brian Condit

Bridge Net Weight: 330.00 grams

Max Compressive Load: 327.39 lb

Compressive extension at Maximum Comp. load: 11.75 mm

Load Per Unit Weight (Index): 450.96

Rank: 5

Group 8:

Team Members: Bryan Zantos, Derek Gowrylow, Sheena Kapur, sarah Dershowitz

Bridge Net Weight: 350.00 grams

Max Compressive Load: 407.70 lb

Compressive extension at Maximum Comp. load: 17.84 mm

Load Per Unit Weight (Index): 529.48

Rank: 3

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.