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Anchor Bolts: Nominal Embedment vs. Effective Embedment

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Anchor Bolts: Nominal Embedment vs. Effective Embedment

There is often confusion regarding what is meant by nominal embedment of an anchor and what is meant by effective embedment of the anchor. The illustration below will help with this.

Note that the nominal embedment is the distance from the floor surface to the bottom tip of the anchor prior to tightening (see “before” picture above for hnom).  When an anchor is designated:  ½” dia. x 3 3/4POWSD1 on the plans the 3 3/4 is the nominal embedment.  After the anchor is tightened the remaining embedment may be somewhat less due to the upward travel of the bolt into the wedging sleeve.  Anchor bolt inspectors should understand the difference and should not try to enforce nominal embedment after tightening.  If the “after tightening” embedment is less than hef then the embedment is not to specification.

The “effective” embedment hef (shown in the “After” picture) is the value used for the concrete breakout calculations.

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