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# Re: TILTED SHEAR WALLS

• To: seaoc(--nospam--at)seaoc.org
• Subject: Re: TILTED SHEAR WALLS
• From: ErnieNSE(--nospam--at)aol.com
• Date: Wed, 5 Nov 1997 13:53:55 -0500 (EST)

```I haven't done any job with a tilted shear wall before but in my opinion even
if it is tilted, as long as the diaphragm forces are transfered directly to
the top plate in the same direction of the shear wall there is no problem.
For a straight shear wall( no curvature), it's a direct flow of forces from
the top plate thru the plywood to the sill plate, no matter the tilt or slope
of the wall. There is no moment due to the eccentricity of the top plate
relative to the sill plate due to the horizontal projection of the distance
of the between the top and sill plate. There is no actual eccentricity since
there is no moment arm between the external force(horizontal force applied to
top plate) and the internal forces in the shear wall resisting the external
force, they all lie on the same inclined or tilted plane.

On a curved wall, the analysis becomes more complicated. If you assume that
the lateral force at the top is in one direction only and the resultant force
lies in the centroid of the curved shear wall, there is no eccentricity. This
occurs when one side of the building is a full length curved shear wall. If
the wall is shorter than the bldg dimension and there are drag forces, then
the resultant force may not coincide with the shear wall centroid and there
will be eccenticity.

In a curved tilted wall especially with varying angle of tilt, it becomes a
complicated three dimensional problem which I'm sure will have a complex
eccentric force analysis. I may have to use a computer program for it. Even
if we simplify it and assume an equivalent flat plane with the resultant
forces on the top plate  within the same equivalent plane of the wall, there
is still no eccentricity.

One major problem I have with a curved plywood shear wall is that plywood is
only available in flat panels and in applying them to a curved stud wall
face, we have to bend them causing it to be in a buckled position!!!. I
remember reading the report on the results of plywood shear wall testing and
that some of them failed by the buckling of the wall and the plywood pulling
away from the stud with the nails popping out or the plywood tearing away
from the nail head???? With a curved plywood shear wall, I think this is
already in a failed mode and I would not use one unless the loads are very
low and there are other shear resisting elements in the same direction.

This is just my analysis and opinion.