Masonry Magazine October 1993 Page. 28
Walls
Brick masonry walls may be constructed of a single wythe (one unit in thickness) or multiple wythes and can be reinforced or unreinforced. Brick masonry walls may be loaded perpendicular to the plane of the wall or in the plane of the wall. Out-of-plane loads may be caused by wind or earth pressures or by earthquake induced ground motions. In-plane loads may be the dead weight of the structure, live loads or the result of the transfer of out-of-plane loads through wall connections.
Section properties used in the MSJC Code's design equations for unreinforced masonry walls are I, r and Q. Section properties used in the MSJC Code's design equations for reinforced masonry walls are j, b and d. Additional section properties used to compute applied stresses are A, S and k. Effective areas for partially grouted, hollow unit masonry walls are illustrated in Figure 1. Shading indicates net uncracked area, net cracked area and shear area for a cracked cross section. For all illustrations in this Technical Notes, cross-hatching indicates mortar bedded areas. In Figure 1(b), the effective width, b, is taken as the least of s, 6t and 72 in. (1.8 m). In Figure 1(c), the effective width, b, is taken as the width of the grout space plus the thicknesses of the adjacent web and end web.