Multi-story light-frame structures are often built atop concrete podiums. In areas of high seismicity the overturning restraint system used to secure shear walls in these buildings can produce very high tension demands on the concrete anchorage components of these systems; in fact, full-scale shake table testing has measured forces in excess of 100 kips. While the loads can be high, podium slabs tend to be fairly shallow (14” or less), and the design resistance calculated according to code provisions often isn’t enough (ACI 318-14). While anchor reinforcement detailing is addressed in ACI 318-14, the form it would need to take in slab situations is not addressed, and there are design limitations as well. Recognizing this, a small group of practicing engineers, funded by a SEAONC Special Projects Initiative and supported by Simpson Strong-Tie, began an ambitious investigation into how to provide detailing (anchor reinforcing) that increases the breakout resistance of concrete anchors in podium slabs. After their initial investigation was complete, Simpson Strong-Tie continued with the investigation to consider additional factors beyond the scope of the original testing. This presentation reviews the testing and results obtained, including advanced numerical simulations that provide more insight into the effectiveness of anchor reinforcing.
Post time: Aug-18-2019