Rigid Moment-Resisting Frame Walls: The Frame Method of Analysis - The Analysis of Irregular Shaped Structures - page 491

F i g u r e 14.5 Computer model.

CF - M

2 x 1

T =

b

pier

CF + M

C =

1 x 1

b

pier

where F x = axial force applied to the local X axis of the member.

Walls with window openings are more difficult to model, given the number of off-
set loads and eccentrically applied forces at the wall hold-down anchor locations. The
wall model shown on the right side of Fig. 14.5 is tied to the foundation at the bottom
outside corners of the wall and at the center pier location. Since the frame members of
the computer model occur at the neutral axis locations of the wall sections, the hold-
down anchor forces are offset from the neutral axis of the outside pier members. These
eccentricities must be incorporated into the computer model to accurately account for
the effects of the offset forces. The location of the anchor bolts in the bottom plate of the
wall also causes a vertical offset between the shear reaction at the bottom plate of the
wall to the horizontal neutral axis of the sill section. Extensions of the sill members and
pier members can account for these offsets, as shown in the figure.