We just got a new project, and it happens to be a 4 & 5 story wood apartment building. We've never designed a 5 story building and I've been tasked with researching the topic. Particularly, the lateral stability aspects of a 5 story wood structure. Can you point me somewhere? Thanks.
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5 story wood building
- Thread starter Skicat
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Check out
One of them did an article a few months ago on shrinkage compensating tie downs for multistorey shear walls. I think there are also a number of other related articles also.
One of them did an article a few months ago on shrinkage compensating tie downs for multistorey shear walls. I think there are also a number of other related articles also.
msquared48
Structural
Been doing a lot of those recently, and many contractors are specifically asking for the ATS Holddown system in lieu of other holddowns. FYI.
Mike McCann
McCann Engineering
Mike McCann
McCann Engineering
- Thread starter
- #5
OldPaperMaker
Structural
Skicat,
The "2006 IBC Structural/Seismic Design Manual, volume 2", which is published by the SEAOC has a detailed example of a 3-story, light framed hotel structure. In fact, there are two example designs; one for a wood framed building and one for a cold formed steel structure.
The book cost about $70.
The "2006 IBC Structural/Seismic Design Manual, volume 2", which is published by the SEAOC has a detailed example of a 3-story, light framed hotel structure. In fact, there are two example designs; one for a wood framed building and one for a cold formed steel structure.
The book cost about $70.
To add: When you start getting into 5 story wood buildings you need to be confident the contractor has had experience in commercial wood structures. Otherwise you'll likely end up with someone who's done small crap and has squeaked by with poor details.....who will likely be a pain throughout the entire process. complaining about overdesign and "why do I need that blocking", "how come there's so many straps", "is it really a big deal to take a chainsaw to your shearwall?"
Need to make sure the species you're using can handle 5 stories. I dont think the typical SPF will work in most cases. Note plate crushing too especially around areas where you have stacking elevator lobbies, etc where you get larger loads.
Need to make sure the species you're using can handle 5 stories. I dont think the typical SPF will work in most cases. Note plate crushing too especially around areas where you have stacking elevator lobbies, etc where you get larger loads.
DaveAtkins
Structural
To be honest, I have never heard of a five story wood framed building. Before the IBC came out, you could not build higher than three stories with wood, not for structural reasons, but due to the risk of fire. This is why most of the hotels you see along the interstate are only three stories tall. I think the IBC allows five story wood structures only if they are fully sprinkled.
But, even if the Code allows it, is it a good idea?
DaveAtkins
But, even if the Code allows it, is it a good idea?
DaveAtkins
Skicat
Check out this nice link for your answer.
Check out this nice link for your answer.
- Thread starter
- #12
Thanks again for all of your help. We've never seen a 5 story wood structure before. There seem to be 3 main areas of concern. First, the fire protection. I think we have to use fire retardent material. Second, lateral stability. 5 storys of wood in 100 mph wind is difficult. Finally, as previously mentioned, the ability for wood studs to take the huge gravity loads. Thanks again for all of the helpful ideas. I'll be sure to post when I start to crunch some numbers.
DaveAtkins
Structural
cap4000,
I did not research the IBC regarding how many stories a wood framed structure can be. Maybe it is only 4 stories--I don't know.
But your link references the IRC, not the IBC.
DaveAtkins
I did not research the IBC regarding how many stories a wood framed structure can be. Maybe it is only 4 stories--I don't know.
But your link references the IRC, not the IBC.
DaveAtkins
DaveAtkins
Structural
Sorry--my mistake. I did not read the whole article. The article does reference the IBC.
DaveAtkins
DaveAtkins
structuralnerd
Structural
Try LSL studs toward the bottom if you are worried about capacity. They are much stronger, but probably about twice as expensive.
A few notes for taller timber buildings:
* point loads on your top plates get more important and these need to be specifically checked. You may need triple top plates in some cases.
*a change of stud spacing can also effect the top plates.
* ensure that all point loads are followed down to ground.
* transfer of axial loads through floor plates needs to be carefully looked at.
* axial effects from wind overturning can be significant.
csd
* point loads on your top plates get more important and these need to be specifically checked. You may need triple top plates in some cases.
*a change of stud spacing can also effect the top plates.
* ensure that all point loads are followed down to ground.
* transfer of axial loads through floor plates needs to be carefully looked at.
* axial effects from wind overturning can be significant.
csd
I designed a 5-story wood building several years ago under the UBC code. It was difficult to make the bearing walls on the first floor work because of the strength reduction in Chapter 7 for fire resistance. Many structural engineers seem unaware of this reduction.
In the IBC it is found in footnote m of Table 720.1(2). You should check whether this reduction applies to your project.
In the IBC it is found in footnote m of Table 720.1(2). You should check whether this reduction applies to your project.
msquared48
Structural
City of Seattle does allow 5 story wood structures, but must be fully sprinklered. Usually, overall, they are 7 to 8 story structures, with 2 to 3 stories if PT slabs for parking and the podium slab.
Mike McCann
McCann Engineering
Mike McCann
McCann Engineering
Portland, Oregon allows 5 story under the UBC and IBC. Special inspection is required for nailing, stapping, holdowns.
Studs on the lower two floors will be 4x or 3x's depending on the wall layout, height. Regardless the shearwalls will require a wider nailing to work with the tighter nail spacing.
We try to utilize kiln dry plates, or engineered lumber to minimize shrinkage. Typically the majority of the shrinkage over the floors comes from the plates, two top plates and a sill per level at 1/8" per plate (approx) adds up to 3/8" per floor times five levels fairly significant.
If you are putting this on top of a concrete podium it is important to use line loads in lieu of a estimated projected surface load. We have reviewed projects were a non-conservative psf load was use and deflections were a big issues.
Recently heard that lumber is at a 20 year low due to the surplus due to the downturn in the residential market. So good time to go to wood.
Regards,
Studs on the lower two floors will be 4x or 3x's depending on the wall layout, height. Regardless the shearwalls will require a wider nailing to work with the tighter nail spacing.
We try to utilize kiln dry plates, or engineered lumber to minimize shrinkage. Typically the majority of the shrinkage over the floors comes from the plates, two top plates and a sill per level at 1/8" per plate (approx) adds up to 3/8" per floor times five levels fairly significant.
If you are putting this on top of a concrete podium it is important to use line loads in lieu of a estimated projected surface load. We have reviewed projects were a non-conservative psf load was use and deflections were a big issues.
Recently heard that lumber is at a 20 year low due to the surplus due to the downturn in the residential market. So good time to go to wood.
Regards,
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