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RE: Allowable load for anchor bolts

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-----Original Message-----
From: Structure Department [mailto:struc(--nospam--at)]
Sent: Friday, May 25, 2001 10:46 PM
To: seaint(--nospam--at)
Subject: Allowable load for anchor bolts

A usual trend in design of anchor bolt is to use 0.55*Fy or 0.33Fu as an allowable stress which is equal to 21.6 ksi and 19.14 ksi respectively for A307 material. Also based on spacing of the bolts the failure criteria of the concrete is checked which in some cases reduce these allowable stresses and by increasing the distances this problem could be solved.
Based on UBC97 (table 19-D) and IBC2000 (table 1912.2) the allowable loads given for the anchor bolts are much lower than the values specified. For example for 1" anchor bolt base on gross section of the bolt with max. distance between bolts the allowable stress is 4.65 ksi which is less than 0.2*Fy. This condition exist for all other bolts and all the allowable loads with all different distances are in the range of 15% to 0.25% of Fy. Please advise me about these allowable loads and the usual trend in the way that consulting engineer companies design the bolts.
Best Regards,
Ali Karimzadegan
As has been stated here many times before, it would be well worth the modest price ($20.00 or so) to get the publication "Strength Design of Anchorage to Concrete" by Ronald A. Cook, which is published by the Portland Cement Association. Many of the old "rules of thumb" no longer apply, and in particular the consideration of anchor rod steels that do not have a well-defined yield point (which includes A 307 other than Type C) is something that is rather new in the formalized design of anchorages.
Get that pamphlet.
William L. Polhemus, Jr., P.E.
Polhemus Engineering Company
Katy, Texas
Phone 281-492-2251
Fax 281-492-8203