Responsibility of designing the anchor bolts 7

[Robbiee]

Hi all,
With almost every project that involves a pre-eng steel building, the disagreement on who's responsible for the design of the anchors bolts comes up.
The engineer who designs the pre-eng building decides the number, size and material of the anchor bolts, but leaves the embeddment depth to the engineer designing the foundations.
In my opinion, the design of the connections to the foundations needs to be done by the pre-eng engineer, of course after coordinating it with the foundation engineer and requesting the concrete info.
In some cases, the pre-eng engineer decides the type of anchors to use, such as the common L-shaped anchors, which I might think they are not suitable. What do you typically see and do?

 

[jayrod12]

Around here, the Pre-Eng designer provides a size and layout based on their design. However the final design of the anchor bolts is by the foundation designer. If the foundation designer determines that the anchor bolts need to be bigger, longer, spaced out further etc. then that gets relayed back to the pre-eng supplier and they update their baseplates accordingly.

 

[JAE]

For our projects (in the US):

Engineer of Record specifies building layout, general configuration of framing (columns, etc.)
Engineer of Record specifies code, standards, applicable loads to use on the building.
EOR then delegates the design to the PEMB company.
The PEMB company designs their proprietary building system, asking the EOR for various alterations to the original design criteria as needed to meet their system needs.
The PEMB company designs the size, number and material of the bolts ... but NOT the embedment depth.
The EOR determines the bolt embedment depth based on ACI criteria.
The EOR also is responsible to verify that the PEMB company utilized all applicable code, standard, and load criteria specified on the primary contract documents.

 

[r13]

If you want the PEB guy to dictate the type of foundation and member thickness, then you can delegate the responsibility through contract. But it may be unpractical and undesirable, as the building is likely ordered in very early stage of the project, and variables are kicked in during the later design phase that causing changes.

 

[Celt83]

The PEMB company designs the size, number and material of the bolts ... but NOT the embedment depth.

This seems completely backwards to me all of those things are directly related to the embedment depth via the various ACI anchorage checks. I'd take the position if they are doing the base plate design and finding the forces in the anchors they should do the complete anchor design and not just pass the buck on the embedment portion. Are they giving you per bolt forces or are you getting base reactions and then trying to replicate their base plate design to then finally do the embedment checks?

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[r13]

The size, thickness of plate, and diameter of anchor bolt are independent of type of foundation, except the concrete compressive strength, which would be covered in the purchase order. However, the length of embedment has everything to do with the type of foundation (spread footing, SOG with turn down, grade beam...) and reinforcing, and the type of foundation depends on variables such as subgrade conditions, and other considerations.

The subsequent need to revise the PEMB's original design, after it was received and accepted by the EOR, can be considered a change order that bears monetary consequence.

 

[Rabbit12]

The last thing I'd want is a PEMB designer designing the embedment of the anchor rods. I've never tried to get them to do it, but I think at best it'd be a tough sell and they would likely flat out refuse.

 

[malikasal]

I always provide the base plate thickness - anchor bolts dia and locations, and provide the length as well.

what i do is check the adequacy against the concrete failures , and if there is a failure i highlight that as a note under my base plate detail asking the concrete designer to add sufficient rebars reinforcement.



ôIf you don't build your dream someone will hire you to help build theirs.ö

Tony A. Gaskins Jr.

 

[Robbiee]

JAE: That is exactly how it is being done here too,(Ontario, CA), but I agree with Celt83 that the complete design should be by them.
Celt83:
What they typically provide are the base reactions; horizontal and vertical forces.
Now what if the EOR doesn't like the L-shaped anchors they are proposing and wants to use a more expensive headed anchors? are they going to come back with a request for extra saying: we accounted for this type of anchors?

 

[BUGGAR]

Can you imagine a PEMB Engineer figuring out ACI Appendix D?

 

[Blackstar123]

The PEB designers, I've worked with, usually provide the necessary anchor bolt assembly details such as,
material properties,
diameter, spacings, embedded depth of bolts,
size and thickness of baseplates etc
We are then required to design the pedestals/foundations and perform the anchorage checks for the specified service/ultimate reactions.

 

[Blackstar123]

Can you imagine a PEMB Engineer figuring out ACI Appendix D?

When I first started working after graduation, this was the first task I was asked to perform. It took me close to one week, just to understand the provisions for tension checks only.

 

[Celt83]

Can you imagine a PEMB Engineer figuring out ACI Appendix D?

I don't understand statements like this you just trusted them to design an entire building, they are also PE's why can't they do the anchorage engineering? My, very limited, experience is they are all using in house proprietary software to get their structures to work and designing to the nats ass. This might mean they did a full FEM analysis on the base plate to get it to work, If I just take their reactions and run with a standard rigid plate analysis I'd get different anchor forces than what their model is relying on.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[Robbiee]

Buggar,
Here, I think the same Appendix D is called Annex D and it is a pain to navigate and understand.

 

[WinelandV]

Can you imagine a PEMB Engineer figuring out ACI Appendix D?

Judging by the number of times I've seen 2" edge distances to bolt centers, no, no I can't. ;-)

 

[JAE]

PEMB companies won’t design the embedment because:
1. They generally don’t have any information on the foundation design, concrete strengths, surrounding reinforcement, bolt edge distances, etc to do an embedment design
2. They only design in steel, not concrete
3. Their liability insurance doesn’t cover anything below the base floor elevation
4. It is more efficient for the EOR to determine embedment since they have all the immediate knowledge of the items in reason 1 above.

 

[jayrod12]

I've never had a single one give me flak for asking for larger diameter, or a different layout. If you're getting them to increase their baseplate size significantly, or the thickness significantly, then yes I can see that coming as an extra. But to be honest, I've found that their diameters and layout tend to work from the steel side of things. And the only variable that I need to change to get them to work on the concrete side is embedment depth.

I would not want them designing the foundation elements. And to ask them to design the embedment depth, is in fact asking them to design the foundation. That's not their purview, that's the EOR's (or as I'm starting to see lately a different delegated design engineer).

On a side note, I have no idea how some engineers have sold owners on paying them professional fees, only to have them delegate both the superstructure and the foundation designs to other engineers. What they hell are they providing the owner besides someone to coordinate between two engineers for an exorbitant fee.

 

[canwesteng]

Embedment depth is now and always shall be, part of the foundation design, amen. I've never had a disagreement on this. As stated above, they can't design embedment without designing the concrete.

 

[Anonymous_ENG]

I've posted before in a question about sealed drawings and PEMBs, and I work as a sealing engineer at a major PEMB supplier.

Jayrod and JAE have it correct, we check the anchors for the tension and shear requirements of the steel itself, but make no attempt to make any of the concrete checks. We only design the steel, and that is laid out pretty specifically in our contracts. If the EOR desires a different anchor bolt pattern or size, we usually accommodate that for no charge, as long as it doesn't require us to provide a drastically different amount of steel.

BUGGAR (Structural)
Can you imagine a PEMB Engineer figuring out ACI Appendix D?

Most of the more experienced engineers do understand the provisions of Appendix D and Chapter 17 (ACI 318-14 and beyond). Some of the states I seal require an SE license, so I've passed the same 16 hour exam others on this forum have as well.

I know PEMB engineers get a bad name for what they do, but to think we're incapable of understanding a different material or the requirements of it is downright insulting.

 

[r13]

I don't think BUGGAR meant insulting, but reflecting the prevalent sentiment of dislike and distrust of the PEMB designers, who provide those details (spacing, edge distance) that are not shown the slight understanding of the concerns/design difficulties of the structural/foundation designers. I have no doubt there are talent/capable persons in the PEMB industry, but to my disappointment, the industry is so rigid, and incapable of change after years of complains gathered from the design engineers.