Using ASCE 7-22 sooner than I thought

[P1ENG]

I thought it would be another year and a half before I had to worry about using the ASCE 7-22, but I just discovered that the new FL building code (8th Ed) coming effective in January has adopted the ASCE 7-22 (per chapter 35) in lieu of the ASCE 7-16 which should have been adopted since the 8th Ed is based on the 2021 IBC which has adopted ASCE 7-16. I was bummed when I saw that. Merry Christmas to me! Time to buy and start digging into the changes...

Juston Fluckey, SE, PE
Engineering Consultant

 

[EZBuilding]

Would be great to use this thread to highlight some of the changes.

K_d has been removed from the base pressure equation - it is now applied in addition to the G*Q_cp variables in defining a specific pressure.

 

[Boiler106]

all of us in north carolina are still using ASCE 7-10 until 2025!

 

[phamENG]

Boiler - didn't NC just freeze updates to the residential code until 2035 or something ridiculous like that?

 

[XR250]

Boiler - didn't NC just freeze updates to the residential code until 2035 or something ridiculous like that?

Gawd, I sure hope so!
I think I am still using 7-05

 

[P1ENG]

Well, I'm a modular building engineer so I do work for almost all states (licensed in 47 jurisdictions), so I've got to use almost of all of the various years of standards out there. FL just seems to always be difficult (almost as bad as CA). FL also requires real digital signatures. Most other states are lax in their digital signatures (self-signing through Adobe Acrobat) but FL was the first to require that the signature be third-party verifiable. I don't know how this cuts down on fraud, but that's what they did.

Juston Fluckey, SE, PE
Engineering Consultant

 

[ZiggyKS]

So if IBC hasn't vetted through ASCE 7-22 for inclusion into the 2021 IBC it seems odd that a State would bypass this step to incorporate 7-22 when it adopts IBC 2021 as its model code. Hmm.... I'm not a legal scholar but that isn't how I would have advised the State to proceed.
I've recently fought that battle with a local code authority who wanted me to use ASCE 7-22 for the 2022 Calif Bldg Code (CBC) since ASCE 7-22 is the "most current" document. I had to politely school him that the 2022 CBC is based on the 2021 IBC as its model code as amended by the State; and that Chapter 35 in both codes refer to ASCE 7-16. I then had to make him understand that using ASCE 7-16 which has also been vetted by the State and amended to exclude certain provisions or include more stringent criteria is not the same as using an unvetted version of ASCE 7-22. Furthermore, I was not obligated to compare CBC amendments to ASCE 7-16 vs 7-22 since I would be interpreting what I think the State Code Official will do when they go through 7-22. We also had similar discussions with the correct version of ACI 318 to be used for the Project. At the end of the day I was "allowed" to use the codes referenced in Chapter 35 of the CBC.

 

[P1ENG]

I think IBC has vetted it. It is scheduled to be adopted in the 2024 IBC. I don't like mixing/matching different codes/standards either. Just like the 2018 IRC uses 2015 wind values when the 2018 IBC uses the newer wind speeds. I don't do residential except for one client, but I do an engineered approach, not prescriptive because the I just don't use the IRC so I'm not familiar with it. It gets fun trying to justify 107 mph (2018 IBC) when the reviewer is expecting 115 mph (2018 IRC). For fun, the 2018 IRC adopts the 2018 IBC in its chapter 35 (not sure what that chapter is in the IRC). So now we have (2) ways of calculating wind pressures in the 2018 IRC.

Juston Fluckey, SE, PE
Engineering Consultant

 

[phamENG]

P1ENG - in my neck of the woods, the Virginia Residential Code (the state amended IRC) is the governing code for one and two family dwellings. Full stop. Now, chapter 3 gives the designer the option of using an engineer for elements that don't fit the prescriptive formula, but the IRC is still the code.

As an engineer doing a lot of residential work, I find an intimate knowledge of the VRC/IRC to be useful for two reasons:

1) The contractors building these houses aren't just building engineered houses. They're building prescriptive stuff, too. And when faced with a complicated engineered design, they're just as likely to throw away the drawings and build it 'they way their grand-daddy taught them' anyway. So I like to just detail stuff the way the prescriptive code would have it done if it works. If not, I try to keep it as close to prescriptive as I can so nobody freaks out.

2) The IRC is the minimum standard. Sure, I can use engineering principles to prove that something works, but if it's less reliable or robust than the minimum prescriptive requirement, why on earth would I do it? My favorite example of this is a deck beam to post connection. I can run calculations that show that I can through bolt that beam to the side of the post. But the VRC/IRC mandates a bearing connection. So I also require a bearing connection.

 

[P1ENG]

Pham,my biggest question in the IRC concerns braced wall lines. I just can't wrap my head around the requirements or what is actually supposed to be used. No hold downs? I'm coming from shearwalls which always have corner hold downs and braced wall lines may work, but only if you use them as the code intends... I just don't know what is intended. I actually created a spreadsheet to do braced walls if you wouldn't mind taking a look at it (attached to this post). It is set up such that you only modify the highlighted cells and the prefilled values are based on this image:

Juston Fluckey, SE, PE
Engineering Consultant

 

[WesternJeb]

all of us in north carolina are still using ASCE 7-10 until 2025!

Kentucky and Tennessee are in the same boat as this too, outside of a couple metropolitan areas the adopt their codes outside of state regulations.

 

[P1ENG]

Jeb, I live in TN near the KY border. I appreciate when states don't adopt a code just because a new one is available. In most of these midwest states, the old codes work just fine or there would be more building damage which would prompt a change in the code. Indiana (where I moved from) is another good example of a state that is keeping the old codes. They are on the 2014 IN building code (2012 IBC).

Juston Fluckey, SE, PE
Engineering Consultant

 

[phamENG]

P1ENG - I'll admit that this is the one thing I typically diverge from my rule 1, above, on. I hate braced wall calcs with a passion. Diaphragm and shear walls are soooo much easier. Also, the most common need for actual engineering on a house in my area is because braced walls don't work - lot's of big houses looking out at the ocean or bay with nothing but glass on the back wall.

That said, I've looked into braced walls plenty and have a decent understanding of them. There largely empirical, but if you stare at them long enough you can see the engineering logic slowly bleed through. My experience with is limited to fully sheathed WSP houses - I don't believe in designing a house that somebody can break into with a box cutter.

You do have hold downs in these. Because you're essentially taking the full length of the wall (less windows and other lengths that are too short), it's a lot like a perforated shear wall. When you get to the end of the wall, you have certain conditions that must be met. A minimum length of sheathed wall, for instance. If you don't have that, you need a minimum length around the corner. I see this as engaging that dead load around the corner to act as a sort of hold down by way of the mysterious 'alternate load paths' that tend to exist in these houses. If you can't get that, then you have to use a hold hold and it really is just a perforated shear wall at that point.

I'd say don't waste your time on braced wall spreadsheets. There's a code official in Fairfax County here in VA that produced a nice easy one, though it is based on the 2018 IRC. And both Simpson and APA have online tools (APA's is the best). I'm not encouraging you to just trust the black box, but probably better to vet theirs than to try to make your own.

 

[P1ENG]

pham, I created the spreadsheet because you gain so much knowledge (if you can verify you are actually doing it correctly) when you create a tool from scratch. You never have to wonder what the program is doing behind the scene. I spent a lot of time on that spreadsheet manually entering the table values so that I could interpolate and what not. But I haven't used that file since 2019... Like I said, I just don't do IRC except for that one townhome client 5 years ago. Also, I don't have to worry about contractors. All of my work is modular, so rectangular boxes built in a factory. I informed my current residential client (that only does single unit, tiny cabins) before we got started that I don't do IRC and whatever they get from me would be a complete engineered approach. They were fine with that, and I think they have an above average product because of it.

Juston Fluckey, SE, PE
Engineering Consultant

 

[azcats]

IIRC, Florida did this early adoption of ASCE 7 in a previous code cycle. Either 6 or 12 years ago.