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RE: Axial Tension in Masonry

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More often than not, the residential and small commercial structures in South Georgia (and most of the US) are not designed by an engineer.  Go a little further south in Dade County Florida, and you will find well reinforced masonry walls.

You must reinforce the walls for uplift.  I generally also use a double height bond beam at the top in order to develop the anchorage and the top of the rebar.  I presume that you are doing a partial grouted wall.

Harold Sprague, PE
Krawinkler, Luth & Assoc.

-----Original Message-----
From:	Michael D Zaitz [SMTP:mzaitz(--nospam--at)]
Sent:	Friday, July 31, 1998 11:54 AM
To:	seaint(--nospam--at)
Subject:	Axial Tension in Masonry

Think about this one,

The masonry code ACI 530 does not allow masonry to resist axial tension. 
 Any strength in axial tension is neglected.  Now the problem.  TAke a 
60 ft x 30 ft CMU wall structure with trusses spanning the 30 feet.  If 
you have a low pressure, say 15 psf for net uplift, that would give a 
force of 225 lbs per foot of wall.  Typically a bond beam is provided at 
the top of the wall for anchoring a plate to allow anchorage of the 
trusses and would weigh approxiamtely 60 lbs per foot.  Now we have 225 - 
60 = 165 lbs of force remaining.  How would you resist this force 
considering axial tensile strength is neglected?  Typically in south 
georgia (not at the coast)  additional anchorage is not provided.  
Recently we have been adding vertical reinforcement in the wall taking it 
as far down as needed to get the required dead weight (of course 
contractors have complained.)  Any ideas?