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Bond stress in plain reinforcing

Bond stress in plain reinforcing

Bond stress in plain reinforcing

(OP)
I am confronted with evaluating the strength of some base plate anchor bolts (undeformed, but with a standard hook) and embedded 5.5 ft into 3000 psi concrete. Current ACI codes do not permit using plain reinforcing bars and therefore do not specify any allowable bond stress or development lengths for them.

I found in ACI 318-63 (yes, that's 1963, Sect 1801) provisions for evaluating stress on plain bars, but it results in an allowable tension woefully inadequate.

Does anyone have any more recent or accurate data on this??? Any help would be appreciated.
 

http://www.spiraleng.com
 

RE: Bond stress in plain reinforcing

FHWA'a micropile design manual has a grout to smooth steel ultimate bond stress of about 435 psi.  I'm not in my office now  and can't check the actual stress.  You can try looking online for the micropile manual on FHWA's geotechnical publications web site.

www.PeirceEngineering.com

RE: Bond stress in plain reinforcing

Development Length of Plain Bars fy=215 MPa in EHE-91, the last concrete code in Spain that adressed the issue. The compression bars need be developed straight. So if you want to apportion any reduction from full bar section capacity, do it against the averaged capacity on the full straight length capacity for the case.

RE: Bond stress in plain reinforcing

Now development lengths for anchor rods straight and with a 90 deg hook, for A 4.6 and A 5.6 steels. I have pasted the properties of these steels. sigma r stands for fu, and sigma f for fy. Lengths are also based on EH-73 but corrected (as hinted in such code) to more conservative values for the anchor application



Straight,

RE: Bond stress in plain reinforcing

Quoting Aghayere on Anchor Rods. Since this is a modern text it should portraint the US practice as of 2009. Referred ACI Code is 318-08.

Structural steel design: a practice-oriented approach
Abi Aghayere, Jason Vigil
Pearson Education, Inc., NJ

that by the way seems an excellent steel book.

I have found that the EC remits to National Annexes for the bond stress design for plain bars; as soon I find some relevant quote I may add to this body of references.

 

RE: Bond stress in plain reinforcing

Better read, it says National Annexes can modify what said in the Eurocode about bond to plain rebar. That is that the limit bond stress can be taken that accepted for deformed rebar but divided by 2.25

In french...

"Le présent NCCI suppose que la valeur de calcul pour une barre lisse est la valeur donnée au §8.4 de l'EN 1992-1-1 (c'est-à-dire la valeur de calcul pour une barre non lisse du même diamètre, de béton similaire et dans des conditions similaires) divisée par 2,25. Il se peut que l'Annexe Nationale pertinente donne des conseils sur la conception pour l'adhérence d'ancrage de barres lisses."

See Annex A of(attached) Access Steel document giving bond strength of plain rebar as per Eurocode 3.

 

RE: Bond stress in plain reinforcing

(OP)
Thanks, Ishvaaag, for the numerous posts. I'm sure I'll find my answer among all those references.
Much obliged.

http://www.spiraleng.com
 

RE: Bond stress in plain reinforcing

There is no "allowable" development since the code does not provide a value.  If you are looking for an actual value, you might try looking for data from Darwin out of KU.

The hook on the end of smooth anchor rods is seldom, if ever, a standard hook.  The anchor hook is quite a bit tighter and much shorter than a hooked reinforcing bar.

IIRC, The hook had been generally thought to provide the full development, but evidence says that hooked anchor rods do not provide adequate resistance to pull-out.

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