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Re: Moment Resisting Frame

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I am not familiar with the document you reference however normally, other than system restrictions and height limits, the UBC Seismic Zone does not define the R value.  You get to pick the R value from the UBC Tables which per the 1997 UBC could range from 3.5 to 8.5.  Then based on the reference codes for steel and concrete you will have varying degrees of detailing and minimum design loads.  It becomes an economical choice on your part whether it is better to use a high R value with possibly more engineering time involve and possibly more construction detailing or use with lower R value with less restrictions but perhaps higher base shears.

Thomas Hunt, S.E.

edmondo san jose <engr_mondo(--nospam--at)>
12/05/2008 08:41 PM
Please respond to seaint
Re: Moment Resisting Frame



I'm referring to the recently published by The Concrete Society---Guide to the Design of Concrete Structures in the Arabian Peninsula ( I want to use this recomendation together with UBC 1997 seismic parameters:


Ca= 0.060 (minimum from the above guide for Sc soil profile in Zone AG)

Cv= 0.083 (minimum from the above guide for Sc soil profile Zone AG)

R= ? (this is my question--what type of "moment resisting frame" should be using in Zone AG)?

I= 1.0





From: Harold Sprague <spraguehope(--nospam--at)>
Friday, December 5, 2008 10:54:49 PM
RE: Moment Resisting Frame

Apparently you are referencing an older code.  The use of Rw and the term seismic "zones" has been discontinued for quite some time.  

That said, if you are in a region of low seismic risk as set forth in ACI 318-05 Section, you do not need to design for the seismic provisions of Chapter 21.  But you may have some detailing to which you need to comply which is listed in Section  

Regards, Harold Sprague

Date: Thu, 4 Dec 2008 19:40:33 -0800
From: engr_mondo(--nospam--at)
Subject: Moment Resisting Frame
To: seaint(--nospam--at)

For the design of concrete structures located in the arabian peninsula- what does other consider for the "moment resisting frames-Rw" (ordinary or intermediate?) specifically in Zone "0" areas. Also, there's a guide to use a minimum Zone to this areas, termed as "ZAG" with equivalent Ca and Cv values (again using moment resisting frames, is it ordinary or intermediate?). Thanks for any advice.

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