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Re: Relative Stiffnesses of Masonry Shear Walls (Compared to Concrete)

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Bill:

It's called equivalent solid thickness. "Equivalent solid thickness means the calculated thickness of the wall if there were no hollow cores, and is obtained by dividing the volume of solid material in the wall by the face area of the wall" - Reinforced Masonry Engineering Handbook - J.E. Amrhien - 1st Edition, 1st printing, $14.00 and lots of correction pages. This note is under Table B-3, page 159. According to the table vertical cores grouted at 32" o.c.for an 8" wall is 4.9". We used to have (actually still do) a RCT spreadsheet for both block and concrete wall to find the shear forces in the walls as Joe Venuti says. It was in DOS and done in Lotus. I don't think we ever moved it over to Excel as the Lotus command language was not compatible with Visual Basic.

Neil Moore, SE, SECB
neil moore and associates
consulting structural engineers
shingle springs, california


On 9/12/2010 1:55 AM, Joe Venuti wrote:
Bill
Find  E conc.   E mas  use in equations below

H/d for wall piers  either Cant or fixed condition  convert delta to
rigidity.
(Use tables or spreadsheet Amrhein Tables T)

  Add up correctly for each wall line.

Then you have to figure center mass, center of Rigidity and the 5% code
offset.

Figure base Shear

Distribute loads to walls based on relative rigidity and distance to center
of mass.



Joe Venuti,  P.E.
Joven Engineering
La Quinta,  CA
jovenengr(--nospam--at)verizon.net
-----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc]
Sent: Saturday, September 11, 2010 2:38 PM
To: seaint(--nospam--at)seaint.org
Subject: Relative Stiffnesses of Masonry Shear Walls (Compared to Concrete)

   Trying to model a complicated building base. Building is a wood-framed
apartment, 3 storeys (sorry, like the Brit spelling better this time),
sitting atop a "podium" constructed of a thick concrete slab supported
by a forest of concrete columns in the interior, and 8-inch CMU
shearwalls all along the boundary.

The CMU walls have grouted cells every 32".

I'm trying to figure out the shear demand for the walls in this (very)
irregular building, and as it has been a long time, I need to remember
how to show the "stiffness" of those walls acting as shear elements. I
recall that the spacing of grouted cells has a part to play (i.e. the
smaller the spacing the more stiff the wall), and I want to model the
walls assuming they are concrete elements with the thickness of those
elements reflecting the relative stiffness compared to a solid concrete
wall (in effect the masonry walls would be "thinner" than their nominal
thickness in the real world.

I need some guidance here. Anyone?

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