I am designing a temporary lift lug to attach to an overhead concrete slab, and planning to use either two or four 1/2" diameter wedge anchors with 3-3/4" nominal embedment. I am assuming the KBTZ2 is the most common wedge anchor so I'm looking at the technical data for that and am confused looking at the spacing tables. I want to make sure I don't accidentally put the holes too close together to possibly crack the concrete and have the bolts more likely to pullout. What is the recommended minimum spacing? One thing I read on google said that the spacing is typically 10x the bolt diameter but I don't know if that's a rule of thumb or a Hilti spec or what because I can't find any documentation to back that up. The only documentation I can find is a Figure 2 and Table 5 in the Hilti Technical Info and it is totally confusing me. Am I even looking at the correct table?
Hi Sam,
The installation parameters regarding anchor spacing for the carbon steel Kwik Bolt TZ2 (KB-TZ2) can be found on page 302 of Hilti’s Anchor Fastening Technical Guide, which includes both Figure 2 and Table 5.
In Figure 2 and Table 5, two separate cases (Case 1 and Case 2) are shown. Both cases represent installation parameters for the Engineer of Record to consider. For the KB-TZ2 Table 5, you will notice that Case 1 shows conditions that lean toward a smaller edge distance, while Case 2 shows conditions that favor a smaller anchor spacing. Whichever you decide to use (Case 1 or Case 2), it is important to note that the other installation parameter within that same case should be followed. For example, if you decide to follow Case 2 for an installation that generally leans toward a smaller anchor spacing, the edge distance requirement from Case 2 would also need to be met. Mixing Case 1 and Case 2 conditions would not be recommended, but linear interpolation between Case 1 and Case 2 is possible following the verbiage in footnote 1.
Additional information can be found in ESR-4266.
Please feel free to reach out to hnatechnicalservices@hilti.com if you have further questions.
Best,
Sinan
