Page 423 - Design of Reinforced Masonry Structures

6.74 CHAPTER SIX

bending. In some cases, gravity loads are not transmitted directly to wall; rather they are
transmitted to roof trusses or beams, which are supported on columns or pilasters. In that
case, the wall can be assumed as supported on three sides (pilasters as vertical supports and
foundation as the horizontal support), and free at the top.
Design of wall panels can be simplified under certain simplifying assumptions. The
support conditions must be idealized in order to determine design forces in wall panels.
At the top, they may be assumed simply supported or free. At the other three edges, they
can be assumed simply supported or fixed. The first step in design involves determining
the proportion of lateral load transmitted to horizontal and vertical supports. Assuming that
flexural resistance and stiffness in both horizontal and vertical directions are known, the
lateral load capacity and the proportion of lateral load transmitted to both vertical and hori-
zontal boundary members will depend on the aspect ratio of the wall panel and the restraint
developed at the edges (i.e., at supports).
A simplified procedure for designing wall panels developed by NCMA is described in
Ref. 6.32, which is summarized here. It involves using curves (Fig. 6.42) to determine approx-
imately the proportion of wind load transmitted in the vertical and horizontal direction.

FIGURE 6.42 Approximate horizontal and vertical wind load distribution [6.32].