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.
For assistance with your design, for suggested anchorage-to-podium slab details, slab design requirements, design calculations and Shallow Podium Slab Anchor product information. Also visit our Structural Engineering Blog for more information.
Here are the recommended steps on how to specify a Shallow Podium Anchor and the accompanying anchor reinforcement.