I have a group of Hilti HUS-EZ's 3/4" diameter installed at various angles due them hitting rebar in the CIP wall.
Is there an allowable angle?
How do I calculate the actual capacity?
Hello James,
Anchor installation angle tolerance is discussed within the ACI 355.2, “Qualification of Post-Installed Mechanical Anchors in Concrete,” provisions. Please reference Section 5.2.2, which discusses drill bit requirements. ACI 355.2 is referenced within each mechanical anchor’s Evaluation Service Report (ESR).
While there is not a specified reduction factor to apply in the instance of an anchor installed at an angle greater than six 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:
- Applying a tension-only load on an anchor installed at an angle will have a tension and shear load applied to the anchor due to the angle. The engineer on the project should take the tension-only load and translate this to a tension and shear load based on the actual angle of the anchorage.
- An anchor installed at an angle will typically have a reduced embedment depth than what was originally specified. 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 result in reduced design concrete strength and bond strength capacity.
- In addition to embedment depth considerations, anchors installed at an angle may need to have reduced edge distance and spacing considered, using a similar approach as the embedment depth above.
- Installing an anchor at an angle will apply additional bending moments in the steel reducing the overall steel capacity. The bending moments and reduction may be considered, at the discretion of the Engineer of Record, to be similar to the design for stand-off connections noted in Hilti’s 2022 Anchor Product Technical Guide.
These are only items to consider for anchors installed at an angle. The final decision to proceed with this installation is at the discretion of the engineer on the project.
Kind regards,
Sinan