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RE: Dead+Seismic for heavy equipment on roof[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: <seaint(--nospam--at)seaint.org>
- Subject: RE: Dead+Seismic for heavy equipment on roof
- From: "Ashraf, Mohammed \(Qatar\)" <mohammed.ashraf(--nospam--at)worleyparsons.com>
- Date: Mon, 26 Jun 2006 07:19:43 +0300
Thanks Bryson and Dave.
The no. is 5% means I need to provide the weight of building should be 1.05 times that of the equipment. The original client document shows composite steel decking and concrete columns. I am planning to change it to RCC beam and roof slab system. Any comments from anybody.
From: Michael Bryson
I believe the number is 5%.
Michael Bryson, SE
Joe, Neil and Mohammed,
Good points by Neil and Joe.
Lateral force, Fp need not be higher than 4x the forces at ground level for equipment above the roof level, per EQ. (32-3) of section 1632 of the UBC/CBC. That's a high lateral load for frames above a roof.
Check overturning of the frame/equipment at the base for dead plus seismic for lateral forces in all directions and find the downward jamb force on the roof beams due to overturning. This may govern over dead plus live. Design equipment connections through the roof framing to the primary frame for any uplift - dead minus seismic.
If the overall mass of the building is not increased significantly by the weight of the equipment, say over 10% to 15% of the total mass, it may not be necessary to perform a lateral analysis of the entire building. This is listed in the code for existing buildings. If the building has poor seismic design, such as older, poorly connected masonry and concrete wall buildings with wood roofs, unreinforced masonry buildings or older steel moment frame buildings, it may be advisable though. In that case you can recommend it be done (in writing) and list it as not included in your scope of work.
Good luck getting the project,
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