In a message dated 4/14/99 8:19:38 PM EST, NDZ28(--nospam--at)aol.com writes:
<< Does anyone know of any programs that would facilitate the design of
shear walls and analyze plywood rigid/flexible diaphragms. Even a good
sheet would help, but I wouldn't even know how to start one i.e.; Excel.
When looking at some of the available commercial programs, take a look at how
they address holdown assembly deflection (stretching, oversized holes, wood
shrinkage, crushing, etc.) since these greatly influence the shear wall
deflection. How they evaluate the allowable holdown size based upon drift
load forces vs. working stress design forces. Also how do they address
overturning forces from walls above, and do the upper floor walls which stack
include the holdown deflection from the floor directly below. The typical
detail of a holdown above and below the floor line at the upper floors
increases the amount of shear wall deflection (two holdowns should be
considered for deflection).
If you write your own program, I suggest that you include flexibility for
setting nail size and spacing for individual walls, holdown sizes and
corresponding deflection characteristics, amount of wood shrinkage to
include. The more flexibility the better for adjusting variables, especially
if you have to evaluate an existing wood buildings.
Be aware that certain codes being developed want you to increase the
calculated shear wall deflection by 1.25 due to dynamic effects. The best
program will be one which iterates on its own so all walls that you enter
into the program (2,3,4,5,6 walls etc.) will have the same deflection. You
may find it very time consuming, if you have to keep changing a variable such
as holdown size for individual walls till you get all walls to converge to
the same deflection (say +/- .01" difference between the maximum and minimum
wall deflection for all walls analyzed, remember that you are likely looking
at a maximum allowable drift of around 0.5" for an 8'-0" wall).
The deflection of these individual walls can then be used to determine wall
stiffness to do the rigid diaphragm analysis. Based upon the rigid diaphragm
analysis, you may have to increase the wall strength (holdown sizes) to meet
the increased forces due to torsion. Hopefully in the near future, the
commercial computer programs will be able to handle this.