When designing an anchor fixed to core filled block work, is it appropriate to assume concrete as the substrate for anchor design?

Hi Jack,

Thanks for contacting Hilti.

This consideration falls outside of the testing we have performed on our anchors based on their testing criteria covered in the relevant EAD documents, which means that using this approach would be based on your engineering judgement.

Having said that, it is important to highlight the type of anchors you might use for this and their working principles. If you decide to make this decision, it might be a better choice to go ahead with chemical anchors as they distribute the loads uniformly along their embedment depths, which would help with both the concrete fill and the actual block wall thickness on the outside of that wall. You could possibly design for your chemical anchors to have their design embedment depth completely inside the concrete fill and using the fill's characteristics as your design inputs as a worst-case scenario approach.

Mechanical anchors generally work using keying, undercut or expansion effects, and they might not be set correctly if those effects happen close to where the block wall and the concrete fill meet, especially when following the spacing and edge distance requirements these anchors call for. This is why mechanical anchors might not be the best option to use in such an approach.

I hope this helps you with your engineering judgement about this design approach. Please don't hesitate to reach out should you have any further questions.

Best regards,
Ask Hilti Team.

Thank you,

I'll look at a conservative design using chemical anchors.

A follow up question, is it still recommended not to fix through the mortar joint of the blocks even if they're core filled?

Thanks,
Jack.