Can we obtain a reasonable capacity of an inclined anchor? The design load is very low but the anchors were installed at an angle(45degrees)/not perpendicular due to heavy presence of slab reinforcement. Hence, we need to justify the capacity of the already installed anchor.
Hi Chathura,
Yes, we can obtain a reasonable capacity of an inclined anchor. Kindly raise the request for design here.
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 and bond strength capacity.
- 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 the discretion of the engineer on the project.
Please feel free to reach out to us for additional query.
Regards,
Team Ask Hilti SEA