Originally Posted by
Bill Wieczorek
What would make a beam twist as shown, maybe a fire perhaps.
Asymmetrical loading. Have you ever seen a beam where the support post was off center? That's how it starts. As the beam rotates a little the loads become more and more asymmetrical causing the beam to rotate a bit more causing the loads . . . The higher the height/width ratio the more a problem with those off center loads.
Does it ever happen? You bet it does. It is more common on tall, skinny beams.
I did the repair on a double wood lam beam that had rotated so much the bottom of the beam had moved almost 6". That beam was very deep (vertically) - maybe 14" - and was very narrow - two 2 1/2" or 3" widths - so the height/width ratio was high. There were one wall framed into the beam near the far end but there were no lateral braces along the rest of its length and the near end of the beam was free to rotate in the beam pocket.
This tall, skinny beam was balancing on a few teleposts. Try balancing a credit card on edge on the end of a pencil between your hands and squeeze. That should give you an idea of how precarious this arrangement was.
Everything is fine if the beam is perfectly aligned with the post but, as we know, this does not always happen.