Seismic design base shear to ASCE7-16

[EngrRC]

I am designing a tall building to ASCE7-16. I have designed the superstructure using response spectrum demands (scaled to match the equivalent static force base shear). However, I am designing the foundation based on overturning moments from Equivalent Static as mandated by the approving authority. However, in my understanding, I should be allowed to use the response spectrum foundation loads (roughly 1/5 of the overturning moment). This leads to massive difference in pile loads.

What are your thoughts on this?

 

[driftLimiter]

If AHJ says you need to use ELF for foundations I don't see how you can get around that. However you could consider use of ASCE 7-22 12.13.4 if permitted. The intent of this section is to address the issue that you present. But If you are saying that RSA gives you 1/5th the overturning of the ELF, something feels off there thats a massive difference, it suggests that most of the mass participation is wrapped up in higher order modes.

If you have already verified that the base shear from RSA matches the ELF, have you investigated why the 1/5th overturning demand? Check mode shapes and mass participation etc. ??