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RE: FEMA 350 and SMRF's

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In general, FEMA 350 section 2.6.1 Material Specifications recommends the use of A992 or A913 for SMRF's due to their more well defined properties. A992 is similar to A572 Gr50 but has max and min yield strengths.  Note that this is a recommendation and it is acceptable under FEMA 350 to use the specifications and grades permitted by the 1997 AISC Seismic Provisions although there are some material overstrength factors to apply depending on your choice. 
 
There are now 8 prequalified connections for SMRF's with certain member size restrictions.  FEMA 350 provides detailed design criteria for each option.  For an RBS system, FEMA 350 section 3.5.5 Table 3.6 limits the materials for beams to A572 Gr50, A992 or A913 Gr50/S75 and materials for columns to A572 Gr50, A992 or A913 Gr50 and 65. Column sizes may be from  the W12 or W14 tables.  There is a host of other requirements but if you can meet them, no testing is required.
 
FEMA can be reached at (800) 480-2520 to order books, although I ordered 4 publications over a month ago and they still haven't arrived.
 
The AISC Seismic Provisions and supplements can be downloaded in PDF format from www.aisc.org.
 
Nicholas Blackburn, PE 


 -----Original Message-----
From: Pat Clark [mailto:bcinc(--nospam--at)nanosecond.com]
Sent: Wednesday, February 07, 2001 5:01 PM
To: seaint(--nospam--at)seaint.org
Subject: FEMA 350 and SMRF's

I have two questions regarding a SMRF and the new FEMA 350 guidelines. I am designing a moment frame in a single family residential project, employing an RBS (reduced beam section). 
 
First, FEMA requires cyclic testing of RBS moment frame connections on all SMRF's.  Does anyone know of any tests done on sections from W10 to W18? I know that these sizes are considered small for frames, but often in residential construction I now find myself designing moment frames. Am I limited to OMRF's?
 
Second, I don't have the new FEMA 350 guidelines, and a plan checker has insisted that it specifies only A572 Grade 50 steel for all moment frame beam and column connections.  I design all of my steel frame connections with an increase in yield strength to grade 50 to compensate for the expected yield stresses for A36 steel, but still specify A36. Does someone have this publication?
 
Any help would be greatly appreciated.
 
Pat Clark, P.E.