ASCE 7-16 vs 7-22... use higher Sds?

[Larryhd2]

In CA ASCE 7-16 is still the reference standard until 2026. Do any of you look up the 7-22 seismic numbers and compare to the 7-16 to see the difference? I have a site where the 7-22 Sds is 25% higher than the 7-16 Sds. We're not obligated to use the higher number but I'm thinking I should let the client decide. Anyone else do this?

 

[IFRs]

I would certainly make the client aware, and get in writing that they chose one over the other

 

[JAE]

You can always use more restrictive provisions of an updated, but not-yet-approved, code.

Certainly visit with your client.

 

[Harbringer80]

I practice in CA. I don't look up the 7-22 values. A 25% increase in Sds sounds ridiculous.

 

[phamENG]

It may sound ridiculous, but if it's really what the code says, the owner should be aware. What if they want to do an addition in 10 or 15 years, and a little proactive work now could save them several hundred thousand dollars later not having to retrofit a fairly new structure?

 

[Harbringer80]

It may sound ridiculous, but if it's really what the code says, the owner should be aware. What if they want to do an addition in 10 or 15 years, and a little proactive work now could save them several hundred thousand dollars later not having to retrofit a fairly new structure?

If a future addition is planned for in the near future, I'm going to be bringing up a lot of considerations including future lateral load increases. If a future addition is not mentioned I'm not designing for the "future" code, I'm designing for current code.

At the end of year for code cycles there is generally a big push by architects to get projects submitted so the building does not have to be built to the new (more expensive) code.

For projects of any real size, we typically get a geo report and I've never seen a geo report listing future code seismic criteria. The OP can do it if he wants but it is NOT common practice here. It's a rare owner that wants to pay more to get their building built.

Additionally, the 2025 California Building Code is not out yet and could amend the 7-22, though admittedly this is unlikely.

 

[phamENG]

If a future addition is not mentioned

Just because they didn't mention it doesn't mean they don't expect us to some how realize their plans as though they're some kind of self-evident truth. We can bring value by bringing these things up for their consideration and discussion. Plenty of people aren't aware that our understanding of seismic risk is still evolving, as are the methods we use to calculate the potential forces. Doesn't mean you have to design to it, but most sensible owners would at least appreciate being made aware of it.

 

[Aesur]

I'm not against advising a client that there exists a change, however I would make sure that there is an actual change, sometimes there are adjustments on the backend that result in the same design. IE, look at wind speeds, they have continually changed, but so too have the coefficients and often you get very close to the same results. Snow updates is another area, it went from ASD to Ultimate level from what I recall in the latest updates. That being said, don't just assume it's higher without looking at the rest of the code.

Note: This is just being cautious, I'm not all that familiar with the newer ASCE yet as it's not adopted where I practice yet.