I am reaching out in hopes that you can assist with optimizing an anchor design for a light pole system. The contractor inadvertently omitted the embedded anchors in the concrete piers intended for the light poles.
We are seeking your assistance in specifying an appropriate Hilti post-installed anchor system. Based on our analysis, the only anchors that satisfy both the loading and geometric constraints are the undercut anchors from the HDA-P series. Please see the attached Hilti Anchor Design PDFs for reference.
Per the pole manufacturer, the design loads are as follows:
- Pole weight: 75 lbs
- Shear load: 961 lbs
- Moment: 10,465 ft-lbs
Please feel free to reach out if you have any questions or need additional information.
Hi Frank,
Hilti is often asked to provide guidance regarding the retrofitting of cast-in-place light pole anchors with post-installed adhesive anchors. Post-installed anchor design in accordance with the American Concrete Institute Building Code Requirements for Structural Concrete (ACI 318-19) is complex and requires checking multiple potential failure modes. The edge distance from the center of the anchor to the edge of the foundation, spacing between anchors, concrete thickness, and embedment depth are often limiting factors when determining anchor capacity. Furthermore, many light pole bases are typically round in shape, and ACI 318 anchor design is based on orthogonal structures, such as a square shape. The required embedment depth for a post-installed anchor is typically greater than the depth required for a cast-in-place anchor. Since Hilti cannot provide engineering design services, we suggest that you consider consulting an engineer to evaluate anchor capacity. Many design engineers will consider using Hilti’s HIT-RE 500 V3 or HIT-HY 200 (-A/-R) adhesive anchor to post-install new anchor bolts.
Engineers typically consider utilizing a conservative approach to evaluate a round concrete structure by modeling anchor capacity based on the size of a square shape that will fit within the outside diameter. Additionally, engineers will also consider using rebar development theory as an alternate design method to evaluate potential post-installed anchor solutions.
Final selection of a post-installed anchor system will be the decision of the design engineer, who may use anchor design software, simplified design tables, hand calculations, and engineering judgment.
If you have any further questions, please reach out to hnatechnicalservices@hilti.com.
Best,
Kevin