Connector/Drag truss reaction force transfer to foundation
We are stuck in the middle of construction due to a truss issue.
Our GC didn’t review the truss calculations with structural engineer and the trusses are manufactured and installed already. At the time of inspection we found the truss calculations were never submitted.
Now when we submitted the truss calculations (after reviewing with SE) to the city, we got a comment regarding a connector truss.
This connector truss is sitting on a shear wall and has vertical reaction force of 2400lbs. The city plan checker is asking SE how he is planning to transfer this load to foundation.
Now the structural engineer is asking truss company to redo calculations to lower this vertical reaction force. The truss company is not helping much here (very hard to reach out to them and connect with SE).
My questions :
1. In such situation is it possible for structural engineer to come up with a solution without redoing the cals ?
2. Considering the connector truss is sitting on shear wall, isn’t shear wall has enough strength to transfer the 2400 lbs of reaction force to foundation ?
Replies
If it was simple, your SE would have referenced the capability.
since he/she is engaged, just let the process resolve itself.
It depends on how the shear wall is put together, and what the specs are.
It might be fine as it is, or it may require some additional structure (and the more expensive analysis to show that the forces are handled.)
Really not enough info to comment.
Is this all wood-framed construction?
How is the shear wall framed (wood, CMU, concrete)?
What is the foundation that supports the shear wall?
You used the term 'Connector/Drag truss' - this implies a lateral force, yet you refer to a 'vertical reaction force of 2400lbs.'
Who was sitting on the truss calculations?
Who holds the contract with the truss manufacturer & designer?
If the truss manufacturer requested a review of the calculations by the SEoR, why did it not happen before fabrication began?
To your 2 questions:
1. In such situation is it possible for structural engineer to come up with a solution without redoing the cals?
In a word - maybe. Who pays for his/her time? If a truss has to be modified then you'll be back with the truss manufacturer unless the SEoR is willing to take ownership of the design modifications.
2. Considering the connector truss is sitting on shear wall, isn’t shear wall has enough strength to transfer the 2400 lbs of reaction force to foundation?
Can't just assume that without knowing how it's been constructed. Besides, a shear wall is primarily used to resist lateral forces. They often carry minor gravity loads as well, but the combination of all loads may exceed what it can safely sustain. Which is the likely reason that the SEoR is asking if the truss load can be reduced.
Thanks for the responses.
@CT_Yankee : I probably don't have answer to all your questions. The truss company was hired by our GC and we relied on GC to make sure he would do the review and submittal (probably a mistake at our end as we should have handled it ourselves).
Its a wood framed construction. A single story 2500 sqft house with hip roof.
I am not sure how the shear wall is constructed.
I think the SE is also questioning why the connector truss has such high vertical reaction force (it has a horizontal load of 6000lbs also). One of the options he gave to truss company is to redo calculation with 95mph (instead of 110) in the hope that this will bring the vertical reaction force down. We are waiting for truss company's response right now.
Since the SE is not telling anything in detail to me, I was just nervous what kind of problem we are facing here. Does it mean we need to remove the trusses and rebuild it all over again (this would be a significant cost).
Looking at the responses here looks like SE and truss company should be able to find some solution not as drastic as redoing the whole roof.
Thanks for the responses.
Good luck with the resolution.