- To show how a building exhibits the results of a periodic disturbance.
As with any physical system, a building exhibits resonance. In this case, a building has a natural frequency at which it wants to sway back and forth.
If a building is struck once, say by a gust of wind, it will move sideways and then sway back and forth for a short while at it's natural frequency.
However, if a building is unfortunate to meet up with a force which continually disturbs it at the building's natural frequency, a high amplitude resonance may develop to the point where the building suffers structural damage.
This model of a building exhibits the results of a periodic disturbance which is causing it to oscillate in one of it's resonant modes.
There exist skyscrapers which sway so much during a high wind that the workers are sent home at such times!
(Needless to say, this wasn't an intended design feature)