Pan Joist - "Single Tapered End"

[JAE]

I've worked with concrete pan joist systems for years and am familiar with tapered end forms where the end portion of the joist (typically the end 3 feet) is tapered wider to get more shear capacity...usually about 5 to 6 in. more width.

I've got a project built in 1965 where the design plans use the term "Single Tapered Ends" and call for them on the plans for some joists I'm checking.

The problem is, I'm not sure what the "single" means as I've never seen where only one side of the pan form is tapered and the other isn't. On top of that, my field inspection and photos show no such taper occurring in actuality.

The shear capacity doesn't seem to be adequate and the tapers are missing...unless I'm missing something. I wonder if they added stirrups instead?

Anyone ever hear of Single Tapered Ends?

 

[DaveAtkins]

I'm not sure, JAE, but were they supposed to taper the end at the first interior support, where the shear is about 15% higher than at the exterior support?

In any event, it seems like they didn't do what was requested on the drawings.

DaveAtkins

 

[JAE]

Yes, the STE was indicated on all the joist ends except for the exterior support.

I wondered if they didn't have STE's and substituted some small stirrups...but we don't have the equipment or time right now to investigate further at this stage.

 

[DaveAtkins]

I wish I was closer to Iowa (isn't that where you are?). The company I work for owns a Hilti Ferroscan--a great tool for locating reinforcing in concrete.

DaveAtkins

 

[msquared48]

In my 1977 CRSI, pages 8-24 thru 8-71, in the notes at the bottom of the tables, there is mention of square end joists, and "SPECIAL tapered end joists", no reference to single tapered ends. Could this have been a typo?

Mike McCann
McCann Engineering

 

[msquared48]

I also looked at my WSD RC Design Handbook, 3rd edition from 1965, and, at the bottom of page 222, it did reference a note regarding pan joists in Chapter 20 of ACI 318-63. I do not have a copy of ACI 318-63, but maybe someone else does and could check it out?

Mike McCann
McCann Engineering

 

[msquared48]

I did find ACI 318-63 in one of my old textbooks, but Chapter 20 was of no help. This was the governing code when I was in College.

Mike McCann
McCann Engineering

 

[hokie66]

I would guess that they intended alternating tapered and straight pans, thus creating a taper on one side of each joist. I don't think I have ever seen that done, but there would be nothing wrong with the approach.