Buckled steel roof trusses 1

[Teguci]

What repair would you recommend for this situation?

Existing 100 ft span steel roof trusses (fink with monitor) have been exposed to a high temperature and are buckled. The trusses are laterally braced and have only sagged maybe 12". Clearance is not an issue. Buckles occur in the top and bottom chords. The chords (double angles) are twisted and bent out of plane but still hold load. Replacement is not an option so be creative in ruling out future failure modes.

 

[csd72]

Teguchi,

Those 2 items are much harder to carry out than they look on paper, also:

You will not be able to straighten the members to mill tolerances so the repaired arrangement will be much weaker than the (probably) already insufficient structure.

In order to get a metallurgical analysis of the affected area then you will need to take coin tokens from the existing angles at the most critical point.

You will most likely not be able to get access to all the welds to test them.

What happens when the client has spent more money than it would take to replace and they still have not fixed the problem? Risk management is very important on these ones.

 

[JAE]

A previous firm I worked for some years ago had a project where some exposed trusses (this was a municipal auditorium) were exposed to fire. Framing was like a dome (similiar to Astrodome framing but elongated in one direction a bit).

Very contained - explicit area of heat so the extent of material damage to steel was well understood.

The solution was to shore up the remaining steel framing, remove and replace all steel that was exposed to heat - re-welding new shapes to match the original framing.

This is a sledge-hammer response compared with Ron's suggestions above. But it replicated the original framing of a semi-historical structure.