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Re: Steel SMRF on Conc. shearwall

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Gerard and  David:


Thanks for kind responses.

The plan check engineer, which is an experienced SE, has indicated that both steel SMRF and Conc. shearwall to be designed for Em.

On my first email to the SEAINT Listserve, I did not mention that the SMRF is connected to a Steel Collector which brings about 60% of it's total seismic load.

Do you believe that the SMRF should not be designed for Em?

If SMRF does not need to be designed by Em then the Conc. shearwall qualifies for "Vertical Combination" per 1630.4.2. and does not need to be designed for Em either.

Thanks in advance

Casey (Khashayar) Hemmatyar
Private email <k(--nospam--at)>



Wouldn't this qualify as a "Vertical Combination"?  See CBC 1630.4.2 
David A. Topete, SE

Structural Engineer

GFDS Engineers

543 Howard St., First Floor

San Francisco, CA 94105

v : (415) 512-1301 x21

f : (415) 512-1302




It's not discontinuous.

What you do is design the portion above the shearwall using the appropriate R factor. Then you get your reactions from the above structure, scale them by the relative Rtop/Rbot ratios and design the lower portion using the R for the lower system.

It's like treated them as two separate structures where you transfer the reactions from above to below.

It's not a soft story or anything like a vertical irregularity. In tall structures it's something to monitor and examine the combined stiffness effects and drift issues.