On projects in elevated seismic zone where there is significant calculated uplift force on the anchors, deeper embedment depths may be required for the anchor bolts. For these projects it is important that the thickness of the slab is adequate to properly achieve the necessary anchor bolt embedment. For a given anchor bolt diameter and embedment there is a chart in the anchor bolt product manual and in the anchor bolt ESR report that gives the required slab thickness needed.
Here is an example:
Project requires ½” diameter Powers SD2 anchors with 4 ½” minimum embedment.
Since 4 ½” embedment is not in the table we will extrapolate:
For 3 ¼” embedment the required hole depth is 4” and the required slab thickness is 5 ¾”.
For 4 ½” embedment, add 1 ¼” (4 ½” vs 3 ¼”) to each value:
Minimum hole depth = 5 ¼”. The required slab thickness = 7”.
If the slab is only 6”, that will not work for the 4-1/2″ anchor. The slab either needs to be a minimum of 7”, or the base and anchorage needs to be changed to a lesser embedment. In summary, the required anchor bolt embedment depth must be coordinated with the slab thickness so proper installation of the anchor bolts can be achieved.