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Supplemental Reinforcement Ties

Supplemental Reinforcement Ties

Supplemental Reinforcement Ties

An older spreadsheet I have (based on ACI 318-08) says this in the sheet that deals with tension supplemental reinforcement:

"Note: In situations where the edge distance, from the centerline of bolts to edge of concrete, is less than 1.5 times the embedment depth, it is recommended that containment steel, such as stirrups, be used."

It doesn't reference a section for that statement. Looking in ACI 318-11, I can't find anything that mandates this. I know (in the case of closely spaced bolts) you have to do this to address splitting failure......but I see nowhere that mandates this for other cases for tensile supplemental reinforcement. (The only place I see it elsewhere is in the case where they are trying to prevent side face blowout....and my case is a breakout case.)

Does anyone know of a section in Appendix D (or Chap. 17 in the latest) that requires this?

RE: Supplemental Reinforcement Ties

Quote (WARose)

Does anyone know of a section in Appendix D (or Chap. 17 in the latest) that requires this?

a) Not I. It has the feel of someone's "good practice" commentary rather than force of law.

b) It is common to have edge distances less than 1.5 heff. If supplemental reinforcing were required for all though, you'd think that there's be some flashing red alarms in the relevant ACI sections, the example problems, and our usual software. To my knowledge, there isn't.

c) The reference to 1.5 heff would seem more appropriate to me if tension breakout were the issue rather than shear.

HELP! I'd like your help with a thread that I was forced to move to the business issues section where it will surely be seen by next to nobody that matters to me: http://www.eng-tips.com/viewthread.cfm?qid=456235

RE: Supplemental Reinforcement Ties

Well, I'd point out your spreadsheet only "recommends" it; not requires it. Likely just a "good practices" thing. I don't know of any requirement other than shear in the anchors or side-face blowout failure of the anchors. It's also likely related to the practical aspect of these anchors with low cover being generally on columns on piers which require stirrups anyway either for strength reasons or simply to hold the vertical bars in place during the pour.

I suspect it's related to trying to provide additional confinement at the lap splice to prevent failure from the compression struts in the non-contact lap splice between the headed anchor and the tension reinforcement. It's possible more info is here:

Eligehausen, R.; Mallée, R.; and Silva, J., 2006b,
Anchorage in Concrete Construction, Ernst & Sohn (J. T.
Wiley), Berlin, Germany, May, 380 pp.

But I don't have this paper available.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL, CO) Structural Engineer (IL, HI)

RE: Supplemental Reinforcement Ties

Thanks for the feedback guys. TME, I have that book.....should have thought about it before I posted. Will check there.

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