Date: Mon, 3 Jan 2000 10:13:26 -0800 <GKhosrownia(--nospam--at)spk.usace.army.mil>
It sounds like you need to use a system similar to pre-engineered buildings,
rigid frames plus cold formed purlins and standing seam roofing. Much
cheaper than the conventional framing you are proposing.
Pre-cast panels should be OK in seismic zone 2. I think I have even seen
them in seismic zone 4.
From: Michael Zaitz [mailto:zmanpe(--nospam--at)bellsouth.net]
Sent: Sunday, January 02, 2000 4:07 PM
Subject: Framing Decisions
I have a warehouse building approximately 500' by 320' in dimension. It is
steel framed with joists, girders and tube columns, metal deck, and precast
wall panels. It is a double sloped roof 1/4:12 with the ridge running
parallel to the 500' dimension. The standard bay size is 40' x 40' with the
end bay being 40' x 20'. Due to the length of the building I am putting in
an expansion joint midway down the 500' dimension across the 320' direction.
At present I am running the joist girders parallel to the 320' dimension to
give me frame action for the longitudinal direction. For the transverse
direction I am planning on using the panels as shear walls. Due to the
expansion joint I decided to run the girders as I did and that solves any
stability problems with the frames at the expansion joint.
Here is the problem. By running the joist girders the way I am, the joists
will not be vertical. With the 1/4 in 12 slope and a 24" joist the bottom
chord will be 1/2" out of plumb. Will the joist manufacturer design for
this? Or can the joist manufacturer slope the top chord to allow the joists
to hang vertically and still allow the metal deck to get its required
bearing? Will there be gnashing of teeth trying to do it this way? On a
similar project that the architect was involved in (smaller and not needing
an expansion joint) the engineer ran the joist girders parallel to the long
direction which allowed the joists to slope normally. I can not use
x-bracing to get any stability (owner's request) therefore if I run the
girders in the opposite direction I will need to do a portal frame.
On a separate issue is there any problem using a precast panel in a seismic
zone 2 (Av and Aa of 0.18)?