Need a book? Engineering books recommendations...

Return to index: [Subject] [Thread] [Date] [Author]

RE: COMPRESSION Force On Anchor Bolts/Rods

[Subject Prev][Subject Next][Thread Prev][Thread Next]
There is extensive coverage of the strength of anchorage at various stages
in construction (including the cases you've mentioned) in the AISC Design
Guide Erection Bracing of Low-Rise Structural Steel Frames.

 
https://www.aisc.org/publications/shop.asp?action=displayitem&show=one&id=21
2

One the ACI 318 front, design of anchorage into concrete was intended to be
included in ACI 318, but did not pas sthe ballot process in time. It was,
however, included in ASCE 7-98 and IBC 2000. While inclusion of this
strength information in a load code and building code does not make much
sense to me (should have been in 318), at least it is published and
available.

Charlie

-----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc]
Sent: Tuesday, December 11, 2001 4:42 PM
To: seaint(--nospam--at)seaint.org
Subject: Q: COMPRESSION Force On Anchor Bolts/Rods


QUESTION ONE.

I am obliged to design the anchor rods for a base plate which is NOT grouted
so that ALL forces are transmitted to the anchor rods via hold-down AND
leveling nuts. I gather this isn't an altogether uncommon thing since the
baseplate design program I'm using actually allows it as a condition for
design.

My problem is in considering the embedment of the bolts and the capacity
thereof to resist compressive forces. If I have a steel-plate anchor
mechanism, it seems to me that the anchorage and the encapsulating concrete
are going to see the same kind of effect with the bolts in compression as
from tension, only in reverse (i.e. there will be an effective conical
"pushout" area BELOW the anchorage).

As you might expect, because of the gravity loading the compressive force is
actually GREATER than the tension force in a given bolt.

It seems to me as a first approximation, then, that you'd need at least as
MUCH concrete below the anchorage as would be required above it, to keep the
anchor rod from "plunging" or the anchorage zone from blowing out.

Has anyone looked at this in detail? If so, what design assumptions did you
make and why?

QUESTION TWO.

Using the publication "Strength Design of Anchorage To Concrete" by Ronald
A. Cook, published 1999 by the Portland Cement Association, and which
purports to be a "late draft" of the proposed provisions for design of such
anchorages to be included in the next edition of ACI 318, I have NOT been
able to determine if the designer may utilize surrounding reinforcing bars
that cross "concrete cone failure" boundary to increase the concrete
breakout strength.

I have seen this utilized in other instances, and it is inferred in ACI 318
? 11.7.7 (esp. see the accompanying Commentary), so it seems logical you
could do that in this instance, but I don't see where Cook explicitly
mentions it.

Any comments are very welcome.

Thanks.



William L. Polhemus, Jr. P.E.
Polhemus Engineering Company
Katy, TX, USA
Phone (281) 492-2251
FAX (281) 492-8203
email bill(--nospam--at)polhemus.cc



******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ******** 

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
* 
*   This email was sent to you via Structural Engineers 
*   Association of Southern California (SEAOSC) server. To 
*   subscribe (no fee) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions to seaint-ad(--nospam--at)seaint.org. Remember, any email you 
*   send to the list is public domain and may be re-posted 
*   without your permission. Make sure you visit our web 
*   site at: http://www.seaint.org 
******* ****** ****** ****** ******* ****** ****** ********