HVAC seismic design criteria?

[John_187]

Hello, does anyone have seismic design criteria experience? I have inherited a project and the specs for HVAC don't mention any seismic restrains, isolators etc (only non-seismic). However, I think this may be incorrect. The location is seismic design criteria D, which at face value seems to be "medium" in seismic activity. It would seem to require some seismic restraints, wtih some exemptions.

Thanks for any feedback

 

[lukaiENG]

We normally have delegated design verbiage within our specifications, putting the onus on the contractor - if it works with timing this is probably your easiest approach. In my experience the local contractors understand the requirements intimately as they have to deal with them on every project. As a designer who works across many jurisdictions, I'm less likely to meet the exacting requirements/whims of the local AHJ.
Also, I would have a chat to the structural engineer for your project, they probably have some familiarity with how the local seismic requirements affect equipment and piping etc.
Only once have I come across an AHJ who insisted on having the seismic details on the permit (design) drawings, this was a pain at first, but as it turned out they actually had a some fairly prescriptive requirements which made detailing relatively easy.

 

[PEDARRIN2]

We also delegate those things out.

But we also have an adequate overall understanding of seismic design to be able to direct the contractor to a more precise path.

For a seismic category "D", as you stated, you will have some required restraints with some exceptions. You will need to determine the importance factor of your equipment and building and also coordinate with your structural counterpart on some items.

 

[GT-EGR]

You need more information than just the design criteria letter, the majors ones are usually listed on the structural drawings
Risk Category (nature of occupancy is a hospital or a shed)
In ASCE 7 chapter 13 (whichever one is your latest code) - they have a chapter on seismic for non structural components. It assigns special importance to life safety systems, or items containing hazardous materials, or items that have to remain functional after an earthquake (importance factor 1.5).
A lot of the rest of the chapter covers are the specific details on how to exactly calculate those forces, which is tedious and time consuming, and those calcs can be delegated to the installer contractor if your spec is prepared properly. But in the end it sounds like you already have the answer that it is design category D. So you end up having to meet all the exemptions to get out of seismic, which allows for non-critical, positively attached components with flexible connections, and under a certain weight or close to the floor.
If you want the full answer go to ASCE chapter 7 - which it sounds like you are now responsible to know.