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RE: FEMA 356 URM Walls

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I have only used FEMA 356 as a reference, and have not done a full analysis.  That said, I believe you always have to check both.  It may be that there is no deflection controlled mode, but it should say that in the material section.  The highest DCR of both methods is the one used for design.
Best of luck,
Jake Watson, P.E.
Salt Lake City, UT
-----Original Message-----
From: Dan Goodrich [mailto:dang768(--nospam--at)]
Sent: Tuesday, December 17, 2002 11:16 AM
To: seaint(--nospam--at)
Subject: FEMA 356 URM Walls

Hello All,

I have question regarding FEMA 356, and unreinforced masonry walls. 

Section gives deformation controlled expected strength values for bed-joint sliding, and rocking strength. gives force controlled lower bound lateral strength values for diagonal tension, and toe compressive stress.  To determine the adequacy of a wall, you compare the deformation controlled strengths to the force controlled strengths.  If the wall is deformation controlled, you only check the demand to capacity ratio (DCR) of that failure mode?  Similarly for the force controlled walls.

Is it a correct assumption that you don't have to check both the deformation and force controlled DCR's?  This does not seem correct, but some of the language in  FEMA 356, 273, and 274 lead one to this line of reasoning.

Thanks in advance,

Dan Goodrich, P.E.

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