Can Kwik Bolt TZ anchors be installed at an angle other than 90° into concrete? If so, what is the recommended angle range, and what is the impact on the capacity of the anchors?
This other post references an older answer to a similar question, but the link is broken: Kwik bolt at an angle - Reduced capacity, Angle of installatio...
Hi Guido,
I have included a snippet from ACI 355.2 Qualification of post-installed mechanical anchors in concrete explaining the tolerance. ACI 355.2 is referenced in the ICC Evaluation Service Report for each mechanical anchor.
A similar excerpt can be found in ACI 355.4 Qualification of post-installed adhesive anchors in concrete.
If an anchor is installed at an angle greater than 6 degrees from perpendicular to the concrete surface, there are some important items that need to be evaluated from an installation, capacity, and load application perspective:
- A tension-only load applied on an anchor that is installed at an angle will have a tension and shear load applied to the anchorage due to the angle. The designer should take the tension load and translate this to the tension and shear load based on the actual angle of the anchorage.
- An anchor installed at an angle will tend to have a reduced embedment depth than designed. The effective embedment depth (hef) should be reduced to reflect the distance from the end of the anchor (or to the effective embedment mechanism for expansion anchors, screw anchors, and undercut anchors) normal to the concrete surface. This will reduce the design concrete strength.
- In addition to embedment depth, anchors installed at an angle may need to have reduced edge distance and spacing distance considered, using a similar approach as the embedment depth above.
- Installing the nut and washer for an anchor inclined at an angle larger than 6 degrees from perpendicular should be performed with an inclined washer. With a standard flat washer, it may bend during application of the installation torque and also may not allow proper installation of the anchor mechanism.
- Installing at an angle will apply additional bending moments in the steel which will reduce the overall steel capacity and can be calculated similar to the design for stand-off connections noted in the Hilti Anchor Fastening Technical Guide.
These are just items to consider for anchors installed at an inclined angle. The final decision and design is at the discretion of the engineer on the project.
Kind regards,
Sinan