Delegated design of CFS shear walls

[VA-Struct-Engr]

Hi. I am working on a CFS framed project that is designed under IBC 2015. Unlike IBC 2018, IBC 2015 does not reference AISI code of standard practice (AISI S202-15) that allows delegation of this design task to CFS specialty engineer. On this project, we have delegated design of shear walls to CFS specialty engineer, providing them appropriate design loads and other requirements. However, County reviewer is questioning this approach and wants to know what provision of the code allows us to delegate design of lateral system to the CFS specialty engineer. He would like to see this design done as part of contract documents.
I understand what we have done is per industry standard, however, I cannot find any code provisions (per IBC 2015) that allow this. What provisions of the code do other engineers rely on to delegate this design?
Thank you for your responses in advance.

 

[dik]

I haven't done a lot of CFS buildings, but those I have, if I have steel portals or X-bracing (strap on CFS)... I usually do the design. Too often, in these environs, with small projects the contractor is likely to do the work himself (contrary to the drawing notes).

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[phamENG]

What county are you practicing in? I'm in Hampton Roads, and in all of the CFS buildings I've done that's never been an issue. I think a good question to the reviewer would be...what in the code prevents it?

The building code isn't intended to dictate the manner in which a contract is completed between parties, it's intended to ensure buildings don't collapse and kill people. The reviewer shouldn't care what's in the "contract documents"....they should care what's in the construction documents. If that means the contractor has to get calcs and shops done for the CFS before the county will give them the permit and let them break ground, then so be it. Most jobs I've worked on have received approval on the permit with the caveat that they have to submit the delegated design (CFS, trusses, etc.) for approval prior to starting that phase of the work.

 

[VA-Struct-Engr]

The project is in Fairfax County.

 

[StrucDesignPE]

Oh, that explains it. I am also in VA and have worked on several large projects in Fairfax. We have done projects under older versions of IBC than 2018 and have required delegated design for CFS items such as wall framing (but not shear walls). We had no issues previously, but Fairfax (and many other NoVA jurisdictions) are becoming more stringent. I think Pham's suggestion is a good idea.

Is the whole building CFS framed?

 

[phamENG]

Well whatever solution you come up with, please share. I have no intentions of chasing work up there, but I do have a client that maintains connections that way and gets a small project there every now and then. It would be to know what I'd be up against if they ever need me to participate.

 

[VA-Struct-Engr]

The building is 9 stories of CFS bearing walls over concrete podium.

CFSEI's response was similar to pham's, i.e. "... ask where the code specifically states that shear wall design CANNOT be delegated?"

 

[XR250]

9 stories of load-bearing CFS? That does not sound like a good idea. I looked at one that was 8 stories and the lower floors were almost solid studs.

 

[jayrod12]

I don't practice in the US, but around here, regardless of delegated design or not the EOR is still responsible for the delegated design items. Just because you farm out the nitty gritty calculations doesn't mean you're any less liable for the construction. As the EOR, aren't you responsible to review the delegated design submission to confirm conformance with the design loads and applicable codes. A review of the calculations?

Like others have said, perhaps the AHJ want's the design of the CFS shearwalls to be completed prior to releasing the building permit. Which for a project like this, I can get behind that. As soon as you top 4 storeys locally we're into steel framing and concrete planks or something of that ilk. Although to be fair, CFS is rarely used load-bearing here mostly just non-loadbearing partitions.

 

[sandman21]

The code has requirements for deferred submittal IBC 107.3.4.1 Deferred Submittals. Has requirements for what needs to be on the drawings and how deferred submittals are handled

 

[phamENG]

sandman21 - not sure what version you're looking at, but the 2015 Virginia Construction Code (which is the 2015 IBC modified by the Commonwealth of Virginia) has no such section.

 

[phamENG]

I haven't done any CFS that tall, but I'm sure it could be done so long as the architectural layout provides for sensible framing arrangements and dispersal of loads.

I will agree, though, that those drawings and calculations should absolutely be provided before the permit is approved. There's a little too much riding on making sure all the pieces line up to do otherwise. Now if your firm has done several of these with the same design team and contractor, you may be able to get a little leeway - but perhaps not in Fairfax.

 

[Aesur]

I need to start working on the East coast it seems; I have seen multiple posts about deferred items on the East coast that are never deferred on the West coast. Either us West coast engineers need to learn from our East coast brothers or we need to move into their market offering a complete design package and take all their work (joking).

I am curious how you control items such as story drift, drags, etc. when deferring something this tall?

As for the deferred submittals, it is my understanding that engineers can technically defer anything, however the EOR is still overall responsible for the design of his and others work on the project that is of structural nature. I agree with asking what says you can't defer these.

 

[phamENG]

Aesur - I once had an architect ask (only half joking) why he hired the firm I was working for at the time since nearly the entire project was delegated. I sized columns and beams, selected the reinforcement for the floor slab, and then delegated the joists and metal studs (load bearing and LFRS).

I did a federal project in California a few years ago and the fee was laughably small (especially considering the requirement to travel to the site, and since they only gave us about 3 weeks notice for the meeting the plane ticket ate up about 45% of that fee). So we did as we typically do - delegate the steel connections and metal studs. The local reviewer had a conniption fit and demanded that we design everything. He kept demanding details and we kept informing him that it was being delegated and I had to send him copies of the various codes of standard practice showing that this is, indeed, a thing. I didn't mind in principle...I prefer to do the design myself...but my boss at the time had other ideas.

As for story drift, etc., you have to write a really good specification. Of course, by the time you've written an adequate specification, you can usually just go ahead and draw the details, too...

 

[KootK]

I am curious how you control items such as story drift, drags, etc. when deferring something this tall?

I was involved in a forensic assignment for an eight story CFM building where the shear walls had been delegated. Somewhat heroically, the CFM engineer refused to supply the shear walls until the EOR sorted out a myriad of lateral system problems with the building including, drift, drags, and collectors. At some scale, these things basically become almost regular steel braced frames. It can be made to work but, even when delegated, seems to require a minimum threshold of delegated system knowledge on the EOR for it to be done successfully.

Interesting anecdote: in my early career, I once had a seemingly experienced contractor freak out on me because I was delegating the design of the OWSJ. It caught me quite off guard at the time as he was very aggressive with the "what am I paying you for" business and, until then, I'd never given much thought to what we delegated.

 

[XR250]

I've done enough LGS framing design and I've visited enough job-sites to know this is a bad idea. It ends up being too complicated for the metal stud sub to construct properly. IMHO, anything over 3 stories should be red iron framed with LGS infill.