Rigid Moment-Resisting Frame Walls: The Frame Method of Analysis - The Analysis of Irregular Shaped Structures - page 501

14.4 Design of Wall Members
The design method of the individual wall members is the same for pier sections,
headers, and sill sections, as they occur, and is applicable to the members of all wall
configurations.

Bending
The allowable tension and compression stresses for the lumber flanges are provided in
the NDS. 11 Bending in the composite sections must be checked at all locations where
the section properties change. Tension stresses are usually the controlling stress in the
bending section. However, the flanges of the wall sections undergo a reversal of
stresses, as shown in Figs. 14.19 through 14.21. This causes a portion of the wall section
flanges to be unbraced compression and bending elements, which will affect the allow-
able bending and compression stresses. When the ends of the wall are located at cor-
ners, the outside flanges of the pier sections will be fully braced. However, when the
wall section is located in the middle of a wall line, both inner and outer flanges will be
unbraced for compression. The bending stress in the flanges (unadjusted for bracing)
is calculated as follows:

MC
I

f == f at sections wherejointsinflanges or webdonot occur

t c

t

MC
I

f == f at sections wherejointsinflanges or weboccur

t c

n

where I t = total moment of inertia, in 4

I n = net moment of inertia, in 4

M = maximum moment applied to the section, in-lb, in-k

C = distance to extreme fibers, in

Alternately,

IF
C

IF
C

′ ′

M =

tt

or M =

nt

maximum allowable bending

moment of section, psi, ksi

where F t = F t C F C D , assuming tension controls.

Horizontal Shear
The horizontal shear is resisted by the plywood webs, which are primarily stressed in
shear through their thickness t s , listed in Table 1 of the PDS. The total moment of inertia
used for the calculation is based on using all parallel grain regardless of any butt joints.
See PDS Supplement 2, Section A6, and PDS Section 3.8 for allowable shear stress
adjustment factors.

VQ

f

= horizontal shearstressatsection,psi

∑

v

I t

t s