Ask HILTIAskLearnArticles
Ask HILTI

Alpha_gap factor in seismic anchor resistance calculations

Posted by Saab Woutsalmost 4 years ago
Alpha_gap factor in seismic anchor resistance calculations

*Question asked during our webinar “Seismic Anchoring in New Zealand on 31-03”*
For the alpha_gap factor, would assuming 1.0 be the conservative assumption for Hilti bonded anchor design?

seismic,design,anchors,TR 045,alpha_gap

1 Reply
Posted by Saab Woutsalmost 4 years ago
Hilti Verified

The gap factor is independent from anchor type. Applicable for any threaded-end anchor including expansion anchors, undercut anchors and chemical anchors. The gap factor is equal to 1.0 when the annular gap in the base plate is filled with mortar, so the hole clearance is zero. Meaning: the full shear capacity of the anchor can be taken into account in design.

If there is hole clearance between the base plate and the anchor largen than zero then the gap factor is equal to 0.5. Meaning: the shear capacity of the anchor shall be reduced by 50%. 

seismic,design,Shear,anchoring,eota