ATS Shallow Podium Anchor
Many variables affect anchorage design, such as foundation type, concrete strength, anchor embedment and edge distances. Design tools, such as the Simpson Strong-Tie Anchor Designer™ Software, are available to help the designer navigate the complex anchorage provisions contained in the ACI 318-14 reference design standard. Anchor products, including the Pre-Assembled Anchor Bolt (PAB) or Shallow Anchor Rod (SAR) are also available to simplify specification.
An elevated concrete slab over parking, commonly referred to as a podium slab, is a common anchorage/run start type for mid-rise, light-frame construction. These slabs pose a significant challenge to designers when anchoring the continuous rod tiedown system above.
In designing light-frame structures over concrete podium slabs, understand that lateral loads from the structure above will produce large tensile overturning forces whose demands often far exceed the breakout capacities of these relatively thin slabs. Simpson Strong-Tie has thoroughly researched and tested practical solutions that achieve the expected performance in order to provide designers with additional design options. The use of the special detailing of anchor reinforcement shown in ACI 318-14, Anchorage Provisions, will greatly increase the tensile capacities of the anchors.
The concrete podium slab anchorage was a multi-year test program that commenced with grant funding from the Structural Engineers Association of Northern California and was applied toward the initial concept testing at Scientific Construction Laboratories, Inc. Following that test, a full-scale, detailed test program was completed at the Simpson Strong-Tie Tye Gilb Laboratory. The design approach follows code calculation procedures supported by testing of adequately designed anchor reinforcement specimens. Based on the empirical test data, the inner concrete breakout cone plus the added anchor reinforcement each provided a percentage contribution to the measured peak capacity of the entire anchorage assembly. These contributions are distributed to the overall anchorage capacity and the concept is then utilized for each installation condition being considered for the calculation.
Selecting Your Anchor Solutions
Here are the recommended steps on how to specify a Shallow Podium Anchor and the accompanying anchor reinforcement.
- The designer should determine the following:
- Uplift load designs from light frame superstructure
- Project concrete strength
- Slab thickness
- Anchor and/or tension load locations /key plan
- It is recommended to have a key plan with all tension load locations and values. This will help pin point the edge of slab, mid slab and slab step down locations.
- Is it a wind or seismic restraint?
- Scroll down to 'Design Tables' on this page.
- Based on thickness of concrete, and Wind or Seismic, choose the necessary design tables
- Select the necessary table that resembles the design condition (example: mid slab, 2.75" near edge, or 13" near edge)
- For Wind Designs, match the project demand loads with the tabulated Anchor Tension Capacity to select the appropriate Shallow Podium Anchor callout. This callout is noted under the column 'DETAIL ON SHEET SA1'. Note, wind designs will be based on demand vs. capacity.
- For Seismic Designs, since the ductile anchor steel element must govern the design, the designer will base solutions on anchor diameter and strength and will use the Anchor Tension Capacities only as reference. Match the project anchor diameter and anchor strength to the proper detail under the column 'DETAIL ON SHEET SA1'.
- Go to sheet SA1 and find the proper anchor reinforcement detail as called out in the table.
- Download the details and include them in the construction documents.
- Coordinate the details and Shallow Podium Anchor callout on the construction documents.
- Specify this callout and detail on the construction documents.
- For seismic design per Notes for the Designer, footnote 7, the engineer of record will design the concrete slab based on 1.2 Nsa loads.
- Download sample calculations for reference on general ACI 318, Appendix D design procedure.
- Scroll to the bottom of the Design Tables for Notes for the Designer.