Wall stud analysis on a 3 story wood frame building
Wall stud analysis on a 3 story wood frame building
(OP)
I am reviewing a 3 story wood building (platform framing) with 6' foot window headers. My reactions at the end of these headers are R3 (at the top) = 348#, R2 = 3520# (including the 348 above) and R1 (1st floor window) = 6692# (which includes the 3520 above).
R3 is low because it is only supporting the ceiling load while R2 and R1 carry floor loading.
2 2x4 Kings Studs carry a 2414# roof load while
2 2x4 Jack Studs carry R1, R2, and R3.
My information is that the capacity of the 2 jack studs would be 2200#x2=4400# which is LESS than my R1 reaction at the first floor header.
My question is that this appears to be underdesigned. Am I missing something? The load through the Jack studs should be seperated from the loads through the King stud. I did not design the building but am reviewing and believe that this may be "underdesigned" for these header reactions. I thank you in advance for any insight one may have regarding this analysis.
R3 is low because it is only supporting the ceiling load while R2 and R1 carry floor loading.
2 2x4 Kings Studs carry a 2414# roof load while
2 2x4 Jack Studs carry R1, R2, and R3.
My information is that the capacity of the 2 jack studs would be 2200#x2=4400# which is LESS than my R1 reaction at the first floor header.
My question is that this appears to be underdesigned. Am I missing something? The load through the Jack studs should be seperated from the loads through the King stud. I did not design the building but am reviewing and believe that this may be "underdesigned" for these header reactions. I thank you in advance for any insight one may have regarding this analysis.





RE: Wall stud analysis on a 3 story wood frame building
In real life, there are plenty of time where they forget to put the blocking above the header. That is why some people design the king stud to take gravity load so blocking is not needed. I hope I am making sense.
Never, but never question engineer's judgement
RE: Wall stud analysis on a 3 story wood frame building
A testing lab rat once told me "One good test is worth a thousand expert opinions". I believe with a small twist, "One good calculation is worth a thousand expert opinions".
RE: Wall stud analysis on a 3 story wood frame building
RE: Wall stud analysis on a 3 story wood frame building
Mike McCann
MMC Engineering
RE: Wall stud analysis on a 3 story wood frame building
RE: Wall stud analysis on a 3 story wood frame building
My original question was...
Can I combine the capacity of the 2 jack studs with the 2 king studs to carry the reaction of the first floor 6' header. The 4 studs would work but the 2 jack studs alone would be insufficient to support the 6,692# reaction load at this location.
RE: Wall stud analysis on a 3 story wood frame building
RE: Wall stud analysis on a 3 story wood frame building
The header is supported directly by the 2 jack studs, but should the 2 kings studs be considered as well in determining the support capacity.
RE: Wall stud analysis on a 3 story wood frame building
1. You design the king studs only taking wind load, thats it. Then you design trimmer to take the gravity. If you have 3 windows stacking, more than likely your header on the first floor will be longer (because you use more trimmers).
2. You design the trimmer only to take the load from 1 floor above (doesnt see the load from 2 floor above). Then you design the king studs to take all the gravity load from 2 floor above and higher plus wind. This is a little complicated because you ahve to do compression and bending interaction equation.
I think if your windows are not stacked perfectly, then use method 1. If you have windows same size directly one another, I do method 2. I hope I am making any sense.
Never, but never question engineer's judgement
RE: Wall stud analysis on a 3 story wood frame building
RE: Wall stud analysis on a 3 story wood frame building
You stated...
I have struggled with a requirement in the NDS that limits built-up columns with nailed attachment to 3 members.
I did not know this...so essentially the capacity of the studs is limited to 3 members nailed together 6,600# +/-
You stated...
I treat the jacks as built up columns and the king as a verical "beam" since it technically is not required to work in the gravity system
They must work together to resist the gravity/reaction at the 6' header to justify the deisgn.
THANK YOU ALL FOR YOUR THOUGHT OUT INPUT
RE: Wall stud analysis on a 3 story wood frame building
Never, but never question engineer's judgement
RE: Wall stud analysis on a 3 story wood frame building
I do not design wood structures but am analyzing this 3 story wood structure and could see that it probably should have been constructed of 2x6 instead of the 2x4's.
RE: Wall stud analysis on a 3 story wood frame building
Never, but never question engineer's judgement