Why Do Pylons Collapse in Extreme Temperatures?

[CheesyPeeps]

Homework Statement

Extreme temperatures have been known to cause some electricity supply pylons to collapse. Using your knowledge of physics, comment on why this happens.
(This question is an 'open-ended' question and is worth three marks. One must explain the possible possible reason(s) for what is described in the question)
(SQA National 5 Physics Specimen Paper)

Homework Equations

Assuming that 'extreme temperatures' means extremely cold temperatures, p=F/A could be used to show that a build up of ice on the cables connecting the pylons would put pressure on the cables and potentially pull a pylon down.

The Attempt at a Solution

Explaining why p=F/A could be used gives me one mark, but after that, I'm stumped.

 

[BvU]

What material are these pylons made of ?

 

[CheesyPeeps]

It doesn't say anything about material, although in my country, they tend to be steel.

 

[BvU]

Is the elasticity of steel dependent on the temperature ?