Concrete Wall Joints and Corner Details 2

[Guastavino]

Folks,

I'm working up some typical details here and I want to open for comment. See below. I like the corner detail alright, but the joint details I'm working on are a work in progress. I've read through ACI, looked at old detail books, and thought through previous details. Really, there isn't a perfect detail for Concrete joints, as no joint is ever perfect, but I'd like to see people pick these apart and see what other folks have done that has worked well.

As always, disclaimer, these details aren't done...just a starting point for discussion, so no one use them like they are perfect.

Thanks!

 

[TehMightyEngineer]

I don't like the corner detail, lap the exterior rebar with the other exterior rebar, keep the interior rebar as you show it but provide a bar diagonal or around the corner to stop cracking there.

The above images are from this thread here which talks about that corner detail a lot (much thanks KootK, great info from that post).

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[jayrod12]

My only comment would be on the cutting of 3 out of 4 bars. I would instead indicate it as terminate the bars so they fab them in the shop to suit. Every time I ask guys to cut rebar on site it's a bitch fest and they indicate we should've just noted it on the shop drawings so the shop could shear them off and they would install them as indicated. This of course requires the contractor to actually plan out his construction joints appropriately.

 

[TehMightyEngineer]

Hahah, the guys in our shop are the exact opposite, they love being able to build a cage and the just torch out any openings or similar. Probably the difference between precast and cast-in-place. I'd agree with Jayrod though, terminate can mean either cut on site or fab to length.

Here's also a good article from CRSI on corner joints.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[Guastavino]

Great comments. Anyone know what book that image you (TehMightyengineer) posted is from?

Also, is the ACI detailing manual SP-66 worth the money?

 

[TehMightyEngineer]

I've seen the document running around somewhere before but can't recall where; maybe a MacGregor concrete textbook or something. KootK is the one who posted it.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[KootK]

Anyone know what book that image you (TehMightyengineer) posted is from?

This one: Link. It is, however, information intended for a very different kind of joint. We're talking plan view corners though I think.

Also, is the ACI detailing manual SP-66 worth the money?

Tough to say. There's a lot of useful stuff in there but, at your level of experience, it's likely that you'll have already acquired most of it through structural osmosis. You can check it for free online: Link

Here's what the manual has to say about corner joints. I favor the very simple top left detail as it will do for nearly all conditions. In general, what I'm looking for in these connections is:

1) A little closing joint crack control where there's dirt outside and;

2) On occasion, shear friction for shear transfer where I'm treating the wall as a composite shape (shaft walls and occasionally basements).

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Teguci]

- Keep your horizontal bars oriented to the same side of the vertical bars.
- End your straight bars outside of the joint and use longer bent bars to form the reinforcing inside of the joint
- If you have an opening joint use hairpins from both walls into the joint - this is good up to about 90% of the wall moment capacity. If you need full ductility, provide the 45 deg bar through the joint and make sure your hairpins are small enough to be fully developed within the width of the connecting wall.
- I'd show or refer to the control joints on your corner detail. Corner restraint will cause unwanted cracking unless alleviated.

 

[KootK]

From Concrete International's "Detailing Corner" series that utterly rocks. I'd send you the article were it not for the copyright issues.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[TehMightyEngineer]

You mean the one I posted a link to above KootK? I got it on a google search so I hold myself harmless for any infringement.

Professional and Structural Engineer (ME, NH, MA)
American Concrete Industries

http://www.americanconcrete.com

 

[KootK]

Yes indeed. Sorry TME, I missed that. You're going to hell BTW. Somewhat ironically, the logo for the series is the "top left" detail that I mentioned above but that detail isn't mentioned in the article.

I think that most of the coverage in print assumes "stick built" wall cages. I'd be curious to know how prefabrication of cages would factor in, if at all.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Guastavino]

Thanks all. Very helpful indeed. I love the "no-smoking" symbol way of crossing out of the bad details that the CRSI folks used in that article.

As an aside, I think I'm going to write a book one day, and all it's going to be is vetted quality details...because, I know that if such a book existed currently, I would buy it, and every engineer I know would buy it....

And I wouldn't put much text in there describing the basics. It would be a book that only shows abstract (IE everyday) conditions that aren't "typical". That's why Terry Malone's book on Irregular shaped structures is so good. There are 100s of books that talk diaphragms, and 1 that I know of that shows you how to deal with them when they aren't a rectangle.