Hi Team,
I am looking for some clarity on the embedment of a screw anchor, Hilti HUS4-H specifically. With reference to the attached Profis screenshot i have 4 different depths listed for my design. I want to be clear about what the design requires, without being overly conservative.
This design has a 12 thick plate being fixed direct to the concrete substrate.
- Do i need to specify a 165mm long anchor to achieve 153 nominal embedment?
- Why is the embedment depth 105mm? This is significantly lower than the nominal embedment.
- Why does the specification mention 130mm embedment?
- The technical datasheet gives a hole depth of 140mm for a h_nom of 130mm but my anchor length is 165mm
I figure that the ETA is the limiting factor here and is why h_ef is limited to 104.9mm, but I want to understand how the other numbers all relate to what is implemented on site. What are the minimum (130 vs 104.9) and practical (130 vs 153) hole depths required to be drilled on-site?
Hello Sean,
Thank you for reaching out to Hilti.
I hope the attached diagram will help you understand the relative embedment depths for HUS4-H installation.
Effective embedment depth conveys where the loading mechanism for the anchor engages the base material and is generally used for anchor calculations whereas nominal embedment depth is more easily and readily measured onsite, as it is measured from the bottom of the anchor to the top of the base material.
The reason why your specification text mentions 130 mm embedment is because it represents the fact that the threads on the HUS4 – H anchor are 130 mm and that is what governs the anchor failure modes. Lastly, for HUS4-H your drilling depth is generally 10 mm more than the nominal embedment depth.
Moreover, in your specification text, it mentions that your installation has to be done in accordance with hnom2 which reflects to the installation conditions tested as per ETA. To make your specification even better, you can mention the size and length of the respective anchor and the ETA installation method.
I understand that it’s a bit tricky to understand and hence, if you’d like to discuss this in further detail, please reach out to our engineering team >> here.
Hope this helps.
Kind Regards,
Ask Hilti Team
