Truss Failure
Truss Failure
(OP)
I recently looked at a truss failure where the vertical truss member from the bottom chord to the ridge had pulled out vertically from the metal press plate at the ridge. There is a high humidity condition within the attic and there was record snowfalls in the area where it occured. Any thoughts on causation of the failure? I think that the high humidity condition allowed the wood to swell leading the plates to slightly separate from the member. Your thoughts are appreciated.





RE: Truss Failure
If so, and there was a roof leak in the area of the failure wetting the connection, it is possible that swelling due to freezing could have contributed to the plate loosening grip too... Heck, this could have happened too since there was a lot of moisture in the wood as you describe - just a different scenario I suppose.
Then again, maybe this was the critical connection to fail under the high load condition. Was there drifting at the time of failure? Possibly an unbalanced snow condition?
Mike McCann
MMC Engineering
RE: Truss Failure
See if you can contact the mfg or the truss designer who might be able to shed some light on what is going on...
Truss plate might have been too small or placed incorrectly.
RE: Truss Failure
RE: Truss Failure
Design, grade and size of lumber, pitch, span, spacing, loading, etc... all need to be reviewed
RE: Truss Failure
RE: Truss Failure
RE: Truss Failure
RE: Truss Failure
Will this bearing wall added after the fact have any bearing what so ever regarding future truss failure of this building???
RE: Truss Failure
Also the internal bearing might be overloaded?? - maybe
RE: Truss Failure
I am not actually doing this.I suggested this theory to a builder friend of mine whom says I am 100% wrong and that adding a bearing wall down the middle to cut the free span in 1/2 would in NO WAY add to less possible truss failure do to overloading.I said to me that defies logic?
He says the truss always fails in the outter perimeter
In other words towards the outter bearing walls so therefore putting a bearing wall down the middle would in no way enhance the overall structural integrity of the roof truss in this situation??whos right?
Thanks
RE: Truss Failure
The internal bearing will now carry about 5/8's of the total load. This could cause a problem with perpendicualr to grain loading (allowable about 500 psi depending on grade) or might over load the bearing wall or beam below??
Simply - all loading conditons need to be checked.
RE: Truss Failure
http://www
RE: Truss Failure
Underneath all of the rubble, we found a feeding trough which had been suspended from the bottom of the trusses. The trusses had not been designed to support a suspended load and it is probable that this is what caused the collapse.
Best regards,
BA
RE: Truss Failure
Funny you should mention that because it reminds of a failure I ran into many years ago.
Seems like a farmer bought some trusses off the yard - pre-made 24' trusses for residential use.
He put them like 8' oc and hung chicken cages from them.
All went well until the chickens fattened up. You can guess the "rest of the story"
A lot of dead chickens and one mad farmer..