Wood Floor Framing For A Multistory Building

[jhendrix98]

I am designing a 4-story hotel and I am analyzing the typical floor to wall connection. I have a TJI joist bearing on a double 2x4 top plate with a stud wall above and below. After speaking with Weyerhauser, they stated that they assume that the vertical load transfer from the upper studs to the lower studs goes entirely through the rim joist and not at all through the TJI. If that is the case, then the load has to travel eccentrically through the studs to get to the rim board or the 2x4 sill plate (just below the upper stud wall) has to go into cross grain bending. I realize cross grain bending is a bad idea so I designed the studs eccentrically. I'm getting that I need about 4 studs to work for the typical 1st floor wall "stud". This seems very excessive to me, but when I suggested that squash blocks be placed to align with the studs below and above to eliminate that eccentric loading, I get the "we've never done that before" line. Does anyone have any feedback on how I should be analyzing this or how this is typically done in the field? Thanks.

 

[msquared48]

I would think that the combination of the bottom plate of the bearing wall resting on the plywood floor sheathing could span very effectively over the 4" width or so of the truss joists, taking it to the rim joist or blocking.

Weyerhaeuser's statement, though, seems to predicate the use of solid blocking between the TJI's and not TJI blocking.

Unless you have heavily loaded columns coming down where you would have solid blocking over the area of the column, the use of squash, or solid blocking, is not normally used, just sometimes stud alignment floor to floor where possible.

Mike McCann
MMC Engineering

 

[woodman88]

On a four story wood frame structure the first floor studs should be 2x6's. If a 3.5" wide stud is required, then you can easily get 2x4, 3x4, 4x4 studs at 6" o.c. or double 2x4 (2-2x4) at 8" o.c.
Where a rimboard is used, eccentrically loaded studs should be considered. But all of the first floor walls I had have all been bolted to the concrete. So the rimboard sitting on the double top plate had only some effect on the studs.

I am not sure what spacing of studs and what loading you have, so I can not give a better answer.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

 

[AELLC]

Give us floor and roof dead and live loads (plf), floor-ceiling height, floor joist depth, wind criteria, and wood stud species and grade and we can run a number to double-check.

 

[AELLC]

One thing I would look at is the concentrated load at 2nd floor level due to the bearing trimmers of 3 window headers lined up (assuming all windows are lined up)

 

[msquared48]

For 4" stud walls, I spec 2X4@16 for the top two stories, 3X4@16 for the second floor, and 3X4@12 for the bottom story.



Mike McCann
MMC Engineering