Bottom Chord Failure of Wood Roof Truss

[halemaneP]

We have 46 feet span roof trusses for an auditorium. One of the roof truss had bottom chord failure.We have temporary jack supports until the permanent fix is made. The truss failed at the splice. Splice was not at the node point, but almost at the center.

Since it is a clay tiled roof, the roof dead loads are heavy, about 27 lbs per sq.ft My preliminary calculations indicate about 13,000 lbs of tension. splice which failed was done with ordinary steel press connectors, and not bolted. bottom chord is 2, 2X6 commercial grade southern pine.

I plan to use steel plates with turnbuckle to pretension the truss, with both sides supported at nodal points while turnbuckle is turned.

The question is how to make sure that we pre tension to the exact load ?. How we can measure the tension load on the turnbuckle?

 

[Ron247]

If the truss is double-sloped, then 2'-9" is about a 1.5:12 pitch. That does not sound very "trussy" to me. Guess that is a word. Before I spent time on how to pull it together, I would see if it meets the loadings needed. If it is single-sloped, it sounds less trussy.

 

[Ron]

Agree with dik....jack it up, close the gap, restore the splice and remove the jacks....done. Pre-tensioning not required or effective.

Since your condo is only 8 years old, I would suggest you contact a construction attorney as well. You might have a whole range of construction defects and you only have a short time now to make a claim. There are some good construction attorneys in Central Florida and they can help the association a lot. Unfortunately this site does not have a contact feature so I can't give you a few names of constuction attorneys in your area. I don't want to post them in an open forum.

Further, hopefully your consulting engineer is familiar with the forensic process for condominiums and construction defects.

Good luck.

 

[dik]

I missed the comealong (knew about it, just didn't include it), though... used to 'ease' the parts into place; normally high loads are not required.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[BAretired]

I recall a similar failure on one of my projects, a small branch of a bank. In my case, all of the trusses collapsed, not just one. Fortunately, the collapse happened at night when the building was unoccupied. Snow load was substantial but did not exceed code. Shop drawings specified 16 gauge truss plates, but inspection after collapse revealed they were 20 gauge. Failure was a tension failure of the truss plate.

BA