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RE: Are Roof Top Units considered Dead or Live Loads?

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I have to agree with Rich. I always add the fudge factor in. This
doesn't always work as I worked on a project in which the original
weight given for the roof top unit was 40 kips. Well, before I know it
the weight was increased to 160 kips. 

Keith

-----Original Message-----
From: Rich Lewis [mailto:sea(--nospam--at)lewisengineering.com] 
Sent: Tuesday, January 04, 2005 1:13 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Are Roof Top Units considered Dead or Live Loads?


I don't know about the rest of you, but I have been burned too many
times designing a roof structure to support mechanical equipment.  The
mechanical engineer gives me one weight value and two weeks later it's
different.  Sometimes the construction submittal comes in with different
weights and the steel is already fabricated.  I have learned to add a
"fudge factor" to all mechanical equipment loads on the roof so that I
design the structure once, not 2-3 times.  I have never been able to
recoup the redesign fee of the roof structure from a mechanical
engineer.

I have also had equipment move after being given locations by the
mechanical engineer.

That being said, and considering LRFD load factors, I am inclined to
consider them as live loads.

Rich Lewis
Lewis Engineering
 
 

-----Original Message-----
From: Daniel Boltz [mailto:dboltz(--nospam--at)1st.net] 
Sent: Tuesday, January 04, 2005 8:58 AM
To: seaint(--nospam--at)seaint.org
Subject: Are Roof Top Units considered Dead or Live Loads?

I've had different answers from various Senior Engineers.  Some say that
since the RTU weight does not vary in magnitude and location, it is a
DEAD LOAD.  Others say that if the RTU is changed or moved in the
future, it's weight and location would be considered a LIVE LOAD.  

Any help is appreciated.
--Dan 




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