They (hopefully) calculate stresses and loads on structures BEFORE the building, bridge, airport is built.

Not only do you need maths, mathspigs, to ‘virtually’ destroy the Millenium Bridge in a Harry Potter film, you need maths, obviously, to build the real bridge. Unfortunately, the engineers made a big Boo Boo! They didn’t allow for pedestrian feedback causing sway or wobble. See 10 Biggest Maths Disasters in the World

Here’s a little grab of the maths showing the pedestrian feedback loop causes wobble.

‘ we see that phase of the pedestrians’ feedback force is leading the output displacement of the bridge deck by an angle which becomes exactly at the resonant frequency . This of course is what we expect for a negative damping force.’

Lego engineers need maths.

Lego bridges can be VERY strong.

This is a LEGO MILLENIUM BRIDGE.

But this is NOT a suspension bridge. It is just a model. Here is a FANTASTIC site @ EXPLAIN THAT STUFF showing how bridges work.

A REAL Lego suspension bridge can hold a very heavy load. Here is a Lego suspension bridge built at LegoWorld 2005. The break load for this Lego bridge was 40kg (88 lb). This bridge could support a kid.

Here are two other Lego Bridges. The break load for the next bridge was 76 kg (167 lb). The break load for the third bridge was > 100 kg (220 lb). These bridges could support an average sized adult.

A Neat Lego (Suspension) Bridge on You Tube. *

* Observe neat bridge Vs Unmade bed!

But here is Mathspigs FAV Lego bridge.

Not exactly a suspension bridge but very strong. And this was a kid experiment!!!!!!

Break load = 30.3 kg ( 66.8 lb)

See the next post for some fabulous Lego Maths. In the meantime, if you are going to build a bridge, perhaps, you should do it with maths not love. This is a truly spooky video from Cher and co. Wait for the chorus.