For design purposes, CP 65 classifies the walls, which are defined as having their length exceeding four times their thickness, into :
1 ■ reinforced concrete walls containing a minimum quantity of steel as given in Part 1, clauses
3.9.3 and 22.214.171.124. The steel is taken into account when determining the strength of the walls, and
2. plain concrete walls in Part 1, clause 3.9.4 where only minimum shrinkage steel is provided. The strength of the walls is based solely on the compression capacity of the concrete.
In addition, the walls are classified as :
1 • braced if the walls are supported laterally by floors or other cross-walls
2- unbraced if the walls provide their own stability, such as cantilever walls.
The walls are considered stocky if the slenderness ratio, i. e. Ie/t, does not exceed 15 for a braced wall and 10 for an unbraced wall. Otherwise, the walls are considered as slender.
Figure 2.42 Effective Heights Of Plain Walls
The slenderness limits for reinforced concrete walls are given in Part 1, Table 3.25 of the Code. Th ■ effective heights are determined by similar methods used for columns and in accordance with Part 1, clause 3.8, Tables 3.21 and 3.22, of the Code. When the beams and slabs transmitting forces into the reinforced concrete walls are simply supported, the effective heights of the walls are assessed similarly for plain walls. These are shown in Figure 2.42 above.