Page 350 - Design of Reinforced Masonry Structures

6.2 CHAPTER SIX

of construction practices for walls which may be provided to perform many different func-
tions. Following are some of the many ways in which walls may be classified:
1. Concrete or clay masonry walls
2. Load-bearing and nonload-bearing walls
3. Single- or multiple-wythe walls
4. Solid- or partially grouted walls
5. Un-reinforced and reinforced walls
6. Composite walls
7. Cavity walls
8. Curtain walls, panel walls, and screen walls
9. Veneer walls
10. Empirically designed and engineered (or analytically designed) walls
11. Classification based on support conditions
Various types of walls are described as follows:
1. A wall can be described by the type of masonry units used in construction. Walls built
from concrete masonry units (CMU) are called concrete block walls; those built from
bricks are called brick walls.
2. From the standpoint of loads-carrying function, like walls made from other materials,
all masonry walls can be characterized as load-bearing (or simply bearing walls) and
nonload-bearing (or simply nonbearing walls). Walls provided to support gravity loads,
such as from roofs and floors in buildings, are called load-bearing walls. Sometimes
these types of walls have code-specific definitions. MSJC-08 (Section 1.6) [6.1] defines
load-bearing walls as those that carry at least 200 lb per lineal foot of vertical load in
addition to their own weight. Walls such as those used for fences, interior partitions or
as exterior surfaces of a building (curtain walls and filler walls), highway sound barrier
walls, etc., which do not carry vertical loads imposed by other elements of a building,
are classified as the nonload-bearing type. Such walls are required to be designed to
carry their own load only plus any superimposed finish and lateral forces (Fig. 6.1).
Design of nonload-bearing walls is discussed in Section 6.11.
Loads on a wall may be gravity loads or lateral loads, or both. Gravity loads on a wall
may be concentrated, such as those transferred in the forms of reactions from supported
trusses, beams, and girders, or they may be distributed, such as those transferred by a
supported slab. Lateral loads may be those due to wind, earthquake, earth pressure, or
water pressure. Again, lateral loads may be acting in the plane of the wall, commonly
referred to as in-plane forces, as in the case of shear walls, or they may be perpendicu-

lar to the walls, commonly referred to as out-of-plane forces (Fig. 6.2). In cases where
load-bearing walls also constitute lateral load-resisting system for a building, they are
subjected to combined loads, that is, axial loads (gravity loads) and bending moment.
Although the nonbearing walls, such as fences, curtain walls, and filler walls, do not
carry any gravity load except their own weight, they must resist lateral loads induced by
wind or earthquake.
Codes contain specific provisions for material specifications for both load-bearing
nonload-bearing masonry systems. Specifications for mortar and grout were discussed
in Chap. 2. MSJC-08 Section 1.7.4.4 [6.1] prohibits use of Type N mortar and masonry
cement for lateral force-resisting systems (LFRS) in Seismic Design Categories (SDC) D,
E, and F structures (no such restrictions for structures in other Seismic Design Categories).