Concrete reinforcement in wall, drilled and connection

[Bloogs]

Hey everyone,
Looking for a little guidance on what to do here. Application is for a Footing for a 250’ long steel building with columns 25’ o.c. Building is designed by others, I have the load reactions already. client would like to do drilled piers 4’ deep, 24” diameter that bell out to 4’ diameter at the base under each building column, with a 4’ wall 14” wide across the top of the piers which the base plates for the building will sit on. How do I go about determining the rebar placement in something like this?

Thanks guys.

 

[JAE]

Isn't it just a 14" wide concrete beam spanning across the piers? Not sure what the issue is. If it is a "deep beam" per ACI, follow the ACI code guidance.

I'd be concerned about out-of-plane forces from your pre-manufactured building which are perpendicular to the beam. 14" isn't much to resist larger loads if there are any.

I'd probably at least have a core of 4 vertical bars (with ties) extending up from the piers into the beam full height to secure the beam a bit against lateral "lay-over" type buckling.

 

[hokie66]

So you have the reactions. Why not include them with your question? Gravity, uplift, horizontal?

If the client has progressed the design that far, why hasn't he completed it? "Rebar placement" may not tell the full story.

Are you to be the EOR? As this is your first visit to the site, we have to question your credentials.

 

[Bloogs]

Sorry guys, to add a bit of context. I am a licensed PE, and the eor. I work 99% with farmers and agriculture projects. We’re a small engineering group and don’t claim to be structural gurus by any stretch. for lack of a better explanation, typically whatever the contractor wants to build who’s ‘done it 100 times without failure’ is how things are built. Normally very little if any of my input is taken into consideration. Now where I come in on this one in particular is the lender is requiring it meet code, knowing that most buildings in ag construction do not. Often times I’m working with wood buildings so it’s a simple concrete cookie foundation and done, any wall is just poured between posts, etc.

Here It’s a bit different from what I am used to, so I just wanted a little guidance on what and where to start. And what sections of code in ACI might apply to different segments.

My initial thought was to evaluate the drilled piers alone for the building loads, then evaluate the wall as a beam as JAE suggests, but I’m not sure how to connect the two besides just having a ‘column’ tied inside the wall/beam? It felt like I was having to design and evaluate numerous pieces as individual entities and just throw it all together. It didnt feel right so I thought I would pause and seek guidance before I end up with a mess.

Thanks

 

[HTURKAK]

I think this is perimeter grade beam and transversal direction is not clear . If you have similar beams in transversal direction and the base plates sit on the connections , that will be grid foundation and the connection could be designed as fixed support.
If the steel columns are nominally pin connected to the found. in this case you should need at least tie beams at top level for the tension and stability of grade beams .

You may post more details to get better responds.
..

He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[Bloogs]

This is just one side wall of the building. The other steel columns of the building are supported by isolated, identical drilled piers with 4’ column above grade. The building reactions have horizontal, vertical (and uplift) reactions, there is not transverse support other than soil pressure on the drilled piers and a slab at grade. The beam/wall is entirely above grade.

Please forgive me, I’m obviously new here and evaluating something I don’t usually do.

 

[jhnblgr]

Does the metal building sit on your wall or directly on the shaft foundation? Your wall appears to be simply a concrete wall to keep the building siding above ground and assuming the girts span to columns except for the lower one that would go to your wall. The major force would be wind load it appears. How is the stability of this wall? Is there a floor slab?

 

[Bloogs]

Yes there is a floor slab, at the base of the wall.

The steel building sits on top of this 4’ wall with the opposite side of the building sitting on 4’ concrete columns.

 

[hokie66]

What's the span of this PEMB? Thrust numbers?

 

[Bloogs]

Building is 250’ x 100’
This wall is on one of the 250’ lengths of the building. Has a mid frame support column at 50’. frames are all 25’ o.c.

On the wall section of the building;
Highest horizontal force is 7.9kip, highest vertical is 29.5kip. Greatest Uplift is 8.8kip.

 

[JAE]

typically whatever the contractor wants to build who’s ‘done it 100 times without failure’ is how things are built.

Normally very little if any of my input is taken into consideration

evaluating something I don’t usually do.

All of your comments here raise huge red flags with me. If you are the EOR and the client is requiring this to be built "per code" then the first quote above doesn't apply. Not at all.

If you are the EOR - the second quote doesn't apply. The contractor may have their own ways of doing things but if your are the EOR they should build what what YOU say is required. Not the other way around.

Every engineering state law in the US and other countries usually require engineers to practice only where they have the necessary experience and education. From the third quote above it doesn't sound like you do.

As I said - lots of red flags.

Coming here to get advice is fine but wow...I think you should bring in a consultant who knows something about structural engineering. This for the reason of protecting you against risk and also protecting the public safety and welfare.

 

[Bloogs]

Thanks for your concerns JAE.
Again as I tried to explain, this is an ag building, working with farmers. So the first quote was simply an explanation of why I am trying to design or evaluate this. This is what the contractors usually build and are asking to build again in this situation. In a normal situation the second is also true, normally I’m not signing anything they are simply building on their own and I have no involvement in anything whatsoever. Now that said, I’m well aware that they need to build it however I say it needs to. my up hill battle is that nothing these guys do ever needs to meet code, they never have read engineering plans and just do whatever that they always have done because it ‘works’. I’m just trying to evaluate what they have been doing to see or show that it truly works myself.

I am no stranger to these buildings and seeing foundations constructed like this. I’ve simply never evaluated or designed one, and certainly never stamped one. I’ll never learn if I don’t ask.
At the rate I’m going I will likely scrap the idea completely and do what I have done and know how to do and make them build that instead.