[unclebilly]

I am a professional engineer licensed to work in Alberta.

My 5 minute review of this would lead me to initially look at how these were supported when they bent. Another thought is that they were placed in compressive loading from a bank on either end starting to slip.

I doubt it was a temperature effect - you would need to have very different temperatures from top to bottom on those beams to do that.

The above does not constitute my professional opinion but this is likely where I would begin my investigation if I was involved in the failure analysis based on what I have seen in the above photos and video.