monolithic slab to footing

[McEngr]

Does anyone know where I can find a good reference for designing a monolithic slab to footing? I am interested in designing a foundation for a metal building. I'd like something that can show the limits of using hairpins. Most metal building material only dives into the structural steel. Any help would be appreciated.

 

[scottiesei]

I use "Metal building systems" by Newman.

http://www.amazon.com/Metal-Building-Syste...ie=UTF8&s=books

It has several different foundation concepts and covers hairpins.

 

[McEngr]

I use "Metal building systems" by Newman.
http://www.amazon.com/Metal-Building-Syste...ie=UTF8&s=books

It has several different foundation concepts and covers hairpins.

Thanks Scottie.

 

[McEngr]

I use "Metal building systems" by Newman.
http://www.amazon.com/Metal-Building-Syste...ie=UTF8&s=books

It has several different foundation concepts and covers hairpins.

Thanks Scottie.

Scottiesei,

This book only covers what various types of details and design recommendations look like. From what I've read, it doesn't go into much detail as to how to account for the development length and balancing the mass to kick-out force when volumetrically sizing your footing. Do you have a good design guide book for doing this? Also, what is the requirement for doweling the slab into footing? Is there a design procedure for this? I'm assuming that it would be similar to a spandrel beam to floor slab situation. Is that correct?

Thanks,

McEngr

 

[scottiesei]

There actually is a good discussion on hairpins and WWF crossing in there as well as development length. The majority of the book is concept but hell, we are supposed to be engineers right?!? You basically have a few ways to resist the lateral forces (kick out). You can do it with shear mass and soil friction, or you can tie the footing to the opposite side of the building. To accomplish the latter, you use hair pins and cross a certain # of bar or wires to transfer to forces to the opposite column. Some one borrowed my copy so I don't know what page #'s they were but there is a great discussion on the crossing of the hairpins with the WWF in there.

 

[McEngr]

There actually is a good discussion on hairpins and WWF crossing in there as well as development length.  The majority of the book is concept but hell, we are supposed to be engineers right?!?  You basically have a few ways to resist the lateral forces (kick out).  You can do it with shear mass and soil friction, or you can tie the footing to the opposite side of the building.  To accomplish the latter, you use hair pins and cross a certain # of bar or wires to transfer to forces to the opposite column.  Some one borrowed my copy so I don't know what page #'s they were but there is a great discussion on the crossing of the hairpins with the WWF in there.

The reason I'm looking for an example problem for this is because I've been told to avoid the "grey area" of transferring shear/kickout into a slab on grade. If it's a slab on grade, as I'm told, you will have a tough time getting quality control on the development in a slab that may only be 4" thick. There was a discussion about this on eng-tips.com, but I can't even log on to that darn website! I've tried multiple e-mail / handles and it still won't let me in. I think it's turned into a "click" of sorts.

 

[scottiesei]

That all depends on how big your building is. The smaller the building, the less the concern. Here is a link for the topic at eng-tips that you were looking for:

http://www.eng-tips.com/viewthread.cfm?qid=101604

I have been using hair pins on buildings up to 100' wide successfully now for 7 years. I am however working on a 280' building and am looking into various alternatives. Haven't found anything soothing just yet but am leaning towards tying the 3 main column rows together, possibly with post tensioning. I'm still waiting on the metal building drawings to see exactly what I have to work with.

 

[McEngr]

That all depends on how big your building is. The smaller the building, the less the concern.  Here is a link for the topic at eng-tips that you were looking for:
http://www.eng-tips.com/viewthread.cfm?qid=101604

I have been using hair pins on buildings up to 100' wide successfully now for 7 years.  I am however working on a 280' building and am looking into various alternatives.  Haven't found anything soothing just yet but am leaning towards tying the 3 main column rows together, possibly with post tensioning.  I'm still waiting on the metal building drawings to see exactly what I have to work with.

Scottie,

Thanks for the tips. From what I understand, you would design the wider buildings with a strap beam to transfer the loads. It's the intermediate-sized to very wide sizes that concern me. It seems that a 100' wide frame could get a pretty large amount of kick-out - especially if you have a short/squatty frame with a considerable amount of roof snow. Know what I mean?

As far as I've been told, if the building has especially large forces, you would want to avoid using the hairpins for reasons already mentioned, thus, you'd use a strap beam with top steel reinforcement to transfer the large tension forces.

Is this what you are considering?

Thanks,

Ryan

 

[scottiesei]

Exactly, the issue is that 100' is a very long strap beam hence the consideration of post tensioning. I would consider forces exceeding 20-25 kip land to be large enough to stray away from hair pins.

 

[McEngr]

Exactly, the issue is that 100' is a very long strap beam hence the consideration of post tensioning. I would consider forces exceeding 20-25 kip land to be large enough to stray away from hair pins.

Scottie,

Thanks for your experience. This is the kind of discussion that I'm looking forward to on this website. You've been a great help.

McEngr