Line up multi-story wood studs and trusses?
Line up multi-story wood studs and trusses?
(OP)
I designed a 4-story wood dorm with 2x6 studs and wood trusses both at 16" o.c. On the drawings I had a note that the studs and trusses should line up to avoid loading the double top plates in bending and shear. The contractor has submitted shop drawings for prefabricated wall assemblies. My question is am I being unrealistic in asking things to line up? The building is fairly typical dorm construction in that the long sides of the building are load-bearing, along with the two corridor walls. It will obviously require a great deal of coordination on the wall fabricators part to insure that studs along 4 different walls line up.






RE: Line up multi-story wood studs and trusses?
In the absence of specific (and realistic) guidance in the plans and specs, you will probably have to live with the tolerances (if any) in the local building code as well as locally accepted practice -
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora.
RE: Line up multi-story wood studs and trusses?
RE: Line up multi-story wood studs and trusses?
With that said, in most wood construction, the studs and floor system do not always align, and with a 16" spacing on the studs and trusses, I would not expect there to be any problems if they don't align now.
RE: Line up multi-story wood studs and trusses?
DaveAtkins
RE: Line up multi-story wood studs and trusses?
On timber projects I have designed in the past, I have not included a statement similar to yours for the following reason. Think of it like this. You have 2 - 2x6's spanning 16". Unless you have large point loads (such as mechanical equipment), I would not expect a failure of the double top plates. If there are such loads, I would also check the axial capacity of a stud (it may fail before the double top plate).
Also, if you decide to accept the alternate design submitted by the contractor, I would require that the drawings be signed and sealed by whoever designed it. I would not want to accept the liability for the design of another engineer.
Good luck.
RE: Line up multi-story wood studs and trusses?
With the structure being 4 stories I would be concerned at the first supported floor especially. You will be bringing down three stories on the top plate. (The loads will accumulate as they go down.) On the same note even if the studs do line up you should check for crushing of the top plate perpendicular to the grain. A lot of times this will control and you will have to call out a better species of lumber for your plates.
RE: Line up multi-story wood studs and trusses?
The other thing to keep in mind is that although the loads due accumulate, it is a highly indeterminate structure and there will be a loading sharing effect of adjacent members throughout the structure.
RE: Line up multi-story wood studs and trusses?
I don't know any way to show that a double top plate will check for studs at 16" o.c. for a three or four story building when all the roof and floor loads are being carried by the exterior walls.
That said I have never heard of a double top plate failing. However when I have been the engineer of record on this type of projects I have done several things, none which made the contractor happy. I've specified triple plates which is an expensive option because it does allow for the use of standard length precut studs.
Another thing I have done is detail the bearing with 1"plywood 24" deep nailed to the back of the floor trusses. The plywood then distributes the load from the roof or higher floors to the studs.
What you do depends alot on your level of comfort and I know from talking to other engineers that a lot of people are unsure how to handle the same problem
RE: Line up multi-story wood studs and trusses?
RE: Line up multi-story wood studs and trusses?