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Re: Anchor Embedment

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     The important item to measure is the final anchor embedment depth.  
     The extra depth of the hole given by the Hilti Product Technical Guide 
     is to allow the bolt to "pull up" when the torque is applied to set 
     the anchor.  Without having the anchor actually installed deeper than 
     the minimum embedment prior to torquing, the final embedment would 
     wind up being less than the minimum embedment.  

______________________________ Reply Separator _________________________________
Subject: Author:  "Dave Morris" [SMTP:davem(--nospam--at)] at ENT-01
Date:    9/16/98 2:57 PM

I have a question, particularly for any special inspectors on the list.  For 
expansion bolts we have always specified minimum embedment length on our 
drawings and schedules.  In Hilti's Product Technical Guide (And I assume on 
others) the required hole depth is greater than the embedment by one bolt 
diameter.  This is due to the fact that the load is transferred at the wedge 
not at the bottom of the bolt.  My questions to the inspectors are this:
1) When you are checking depth of holes are you checking against minimum 
embedment or are you checking for the minimum hole depth (which will always 
be deeper for expansion bolts).
2) Does it create problems in the field when the plans list only embedment 
and not minimum hole depth?  Which would you like to see specified on the 
plans? (Both??)
As a design engineer I am very rarely on the job during anchor 
installations.  We depend on the special inspector for these verifications 
in critical applications.  My feeling is that we will need to be more 
specific on our drawings and schedules so it is very clear that we are 
getting the embedment we need.