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RE: Mechanical and Electrical Seismic Loads

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    I guess that I was asking because the unit is not directly connected to the roof. It will set on a steel platform 3' above the roof. I need to design the steel platform for some type of lateral load, that will be dumped into the roof. The piece of equipment that I am designing the support for is a 67,000 lb condenser with ammonia lines running to it. I would like to make sure that my framing has the correct loading into it.

Wesley C. Werner

-----Original Message-----
From: Brian S Bossley [mailto:BSBossley(--nospam--at)]
Sent: Tuesday, February 28, 2006 2:08 PM
To: seaint(--nospam--at)
Subject: RE: Mechanical and Electrical Seismic Loads



IMHO, this would be no different than heavy equipment on a mezzanine.  I think that it would have to be included in your total dead load on your roof, and therefore would have to be in your seismic force calculations.  So, I’d use the seismic factors for your building to calculate the lateral load on your condenser.  But, because you’re in SDC B, section 9.6 would not need to be checked for equipment ANCHORAGE.


- Brian S Bossley  


From: Eli Grassley [mailto:elig(--nospam--at)]
Sent: Tuesday, February 28, 2006 1:18 PM
To: seaint(--nospam--at)
Subject: RE: Mechanical and Electrical Seismic Loads



I don’t understand your question.  If there is an exemption in the Code that says, “you don’t have to design for this,” then why don’t you take it?  There aren’t too many freebees in the Code – so I would suggest you use them when you can.  Use your own judgment to detail the connection so that there is *a* load path for overturning.  Code seismic forces are, at best, just good guesses anyways.


~~ Eli ~~


-----Original Message-----
From: Wesley Werner [mailto:wwerner(--nospam--at)]
Sent: Tuesday, February 28, 2006 6:08 AM
To: seaint(--nospam--at)
Subject: Mechanical and Electrical Seismic Loads



    I am wondering what is the best way to calculate seismic forces on M&E equipment in Seismic  Design Category B. According to ASCE 7-02 Section 9.6.1 mechanical and electrical units in this design category are exempt from the provisions of section 9.6 which deals with architectural, mechanical, and electrical components. I have a large condenser that is to be supported above the roof of the building. Should I treat it as a separate story and just calculate the forces as I would for the rest of the building? Or should I use section 9.6 even though ASCE says that M&E components are exempt for this Seismic Design Category?


Wesley C. Werner