Some code/industry standard questions for Structural requirements for commercial AHU

[tstructural]

I'm a structural engineer but am currently working with a manufacturing facility that produces commercial Air Handling Units. They've asked me to update their Structural Design Checklist for HVAC units in USA. I've come across some information that seems incorrect but don't want to delete it just in case I'm wrong.

FYI - We have pre-approved OSHPD units for high seismic but also sell units in low seismic areas. We provide units for the health care industry as well as others. We also sell to the VA sometimes.

The following are the items that I believe to be incorrect. If I'm wrong - please let me know and also tell me which code I should have so I can see the requirements:

1. if the occupancy importance factor (Ip) is 1.0 and the Seismic Design Category is A, B or C then no IBC certification is required.
2. analytical calculations are acceptable (meaning no testing - just hand or computer calculations) if the Ip = 1.0 and the Seismic Design Category is D, E or F.
3. analytical calculations are NOT acceptable (meaning we would have to test the units on a shake table) if the Ip=1.5 and the Seismic Design Category is C,D,E or F.

For item #1 above - wouldn't our products always have to meet IBC requirements regardless of it being in a low seismic region?
Item #2 and #3 together imply that High Importance (health care and high tech) always require shake table tested units if located in medium to high seismic regions. I've never heard of hand or computer generated calculations NOT being good enough for an IBC certified design

 

[wannabeSE]

I highly recommend reading the first few pages of chapter 13 in ASCE 7-10. I am assuming you are concerned about the equipment requirements rather than the requirements for the equipment's attachment and support. Here are a few comments:

Occupancy Category
For ASCE 7- 10 and the 2012 IBC and later, the terminology changed to avoid confusion with Occupancy classification for the building (A, I , H, R ...) This is now called the Risk Category. The Risk Categories are the same as the Occupancy Category: I thru IV.

Component Importance Factor, Ip
The component importance factor is specified in ASCE 7-10 Section 13.1.3. It is not directly based on occupancy/risk. Ip = 1.5 when:
1. The component is needed for fire-life safety after and earthquake (e.g. smoke control fans in all buildings)
2. The component handles toxic or explosive substances.
3. The component is attached to a Risk Category IV building and is needed for continued operation or the failure could impair operations.
4. The component handles hazardous substances in a building classified as a hazardous occupancy.
If the component does not meet 1-4 above, the Ip = 1.0. Some jurisdictions (OSHPD) consider everything in an risk category IV to have Ip = 1.5. If a suspended ceiling falls, or a coke machine tips over and blocks passage, it will impair operations, so it must be anchored but the special seismic certification requirements may not apply.

Special Seismic Certification
Special seismic certification is required for certain systems in Seismic Design Categories C thru F. There are two types systems that require certification:
1 Electrical and mechanical equipment that must remain operable after an earthquake. This equipment requires certification by shake table testing, experience data, or is inherently rugged.
2. Components with hazardous substance and Ip = 1.5. This equipment requires certification by analysis, shake table testing, experience data, or is inherently rugged. (note this type allows analysis/calculations while the electrical and mechanical equipment does not allow certification by calculations).
OSHPD has a code application notice (CAN) for the 2007 California Building Code (ASCE 7-05) that provides a list of what they consider inherently rugged (pumps, air compressors, etcetera) but the other information may not be current,

http://www.oshpd.ca.gov/fdd/Regulations/CANs/2007/2-1708A.5 rev2.pdf.

OSHPD has a Policy Intent Notice (PIN) that provides background and outlines there requirements for special seismic certification:

http://www.oshpd.ca.gov/fdd/Regulations/PINs/55.pdf

Special Inspection is required to show the equipment installed has the special seismic certification when required. This is required by chapter 17 of the building code.

Attachment and Support
The requirements for attachment and support of all equipment follows different requirements. If you are interested in these requirements, I suggest you read chapter 13 of ASCE 7-10. If you have specific questions, I may be able to help.