SF.2.c Structural failure

What kind of failure happened to these railway tracks, and why?

• Buckling, due to thermal contraction

• Buckling, due to thermal expansion

• Compression failure, due to thermal contraction

• Shear failure, due to thermal expansion

This structure is an architectural example of a...

• Girder

• Simple beam

• Cross beam

• Cantilever

This structure is an example of a...

• Girder

• Simple beam

• Cross beam

• Cantilever

Answer explanation

A 2x4 piece of wood is an example of a...

• Girder

• Simple beam

• Cross beam

• Cantilever

In physics, "moment" refers to...

• A moment in time

• 30 seconds

• A force

• A turning, or rotating action

A door with a doorknob in the centre will require more force to open the same way as a door with "normal" doorknob because...

• The distance between the force and supporting hinge is longer, creating a smaller moment

• The distance between the force and supporting hinge is shorter, creating a larger moment

• The distance between the force and supporting hinge is longer, creating a smaller moment

• The distance between the force and supporting hinge is shorter, creating a smaller moment

Answer explanation

Tire wrenches are tools that tighten/loosen lug nuts on a wheel. Extending the wrench with a longer handle makes it easier to loosen a nut because...

• The distance between the force and lug nut is longer, creating a smaller moment

• The distance between the force and lug nut is shorter, creating a larger moment

• The distance between the force and lug nut is longer, creating a larger moment

• The distance between the force and lug nut is shorter, creating a smaller moment

Answer explanation

A structure begins to tip when the __________ doesn't align with the _________, creating a tipping moment.

• Centre of gravity, Function

• Support, Finger

• Centre of gravity, Support

• Function, Foundation

During high winds or earthquake, a tuned-mass damper is used to align a tower's _________ above the __________, to prevent a tipping moment.

• Foundation, Centre of Gravity

• Centre of Gravity, Foundation

• Height, Ground

• Ground, Height

High wind causes a moment dependent on ________ while gravity causes a moment dependent on _________

• Length D, Length H

• Length H, Length D

• Length D, also Length D

• Length H, also Length H

Answer explanation

a) The moment distance due to wind is the vertical distance from the top of the tower to the bottom foundation.

b) The moment distance due to gravity is horizontal distance from the centre of the foundation, to the COG plumb line. Both wind and gravity moments work simultaneously to tip the structure over.