Overstrength factor with foundation for Cantilever column

[Phatt]

Hi everyone,

I’ve been reading ASCE 7-16 and I’m currently working on a cantilever column system assigned to SDC C or higher. I have a few questions regarding the use of seismic loads with the overstrength factor (Ω₀). From what I understand, the overstrength factor must be applied when designing the connection, base plate, and anchor bolts, as per ASCE 7.

Here are my questions:

1. Should we also apply the overstrength factor for overturning, sliding, and soil bearing checks?
2. For a pier footing foundation, do we need to design both the pier and footing using the overstrength load?
   
   
   
   
   
3. For a single pile foundation, is it necessary to design the pile with the overstrength factor, or is it sufficient to apply it only to the anchors?

I’ve read the following references, but I’m still unclear about how the overstrength factor applies to foundation design in particular:

• https://www.skghoshassociates.com/blog/foundation-overstrength-factor/
• https://www.structuremag.org/article/frequently-asked-seismic-questions/
• 

Thanks in advance!

 

[driftLimiter]

The last sentence of 12.2.5.2 i believe has your answer. Foundation and other elements used to provide overturning resistance at the base of the cantilever column elements shall be designed to resist seismic load effects including overstrength.

In my view the answer to all of your questions is: Yes

In general to my knowledge the only foundation elements requiring overstrength are for cantilever column systems.
But anchorage to concrete is often designed for overstrength based on ACI requirements for seismic zones.