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Block fences (Was: Seismic Design of)

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While seismic design of block fences is a necessary consideration, I also 
think that *wind* design of block fences has also been ignored and could be 
potentially more deadly than seismic.  I say this because people will take 
shelter on the lee side of a block fence in a strong wind (and they *know* a 
wind is blowing), something that would not generally be done just before an 

Locally (Arizona), 4" block fences are touted.  Pilasters are about 10 feet 
apart and contain one #5 bar.  Footing size is such that a proper hook cannot 
be embedded.  Head joints are "interlocking" without mortar.  Drawings  
proffered indicate that the wall is capable of approx. 6 psf wind force,
which, following the letter of the UBC, can be used instead of the generally 
accepted minimum of 10 psf.  However, the only way that I can see that these 
block fences can be considered adequate is to consider that horizontal joint 
reinforcing is capable of taking compression as well as tension despite the 
fact that manufacturers of joint reinforcing state that their product is a 
crack control product only.

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Harold Sprague wrote:


Yes.  I would default to the minimum in UBC 32-3.  Block fences have not
been studied to the extent that they need for proper inclusion in the Code.
With "sound walls" along miles and miles of roads currently being
constructed, it is an issue that needs some attention.  This item is part of
my responsibility as Chair of the BSSC TS 13, and I will be adding it to the
items that need proper study for inclusion in the NEHRP Provisions and
ultimately the IBC.

I appreciate your pointing out the issue.

Harold Sprague
The Neenan Company<<