Civil Engineering Reference
In-Depth Information
Figure 13.16
13.10
DESIGN PROCEDURE FOR CANTILEVER
RETAINING WALLS
This section is presented to describe in some detail the procedure used for designing a
cantilever retaining wall. At the end of this section the complete design of such a wall is
presented. Once the approximate size of the wall has been established, the stem, toe, and
heel can be designed in detail. Each of these parts will be designed individually as a can-
tilever sticking out of a central mass, as shown in Figure 13.17.
Stem
The values of shear and moment at the base of the stem due to lateral earth pressures are
computed and used to determine the stem thickness and necessary reinforcing. Because
the lateral pressures are considered to be live load forces, a load factor of 1.6 is used.
It will be noted that the bending moment requires the use of vertical reinforcing bars
on the soil side of the stem. In addition, temperature and shrinkage reinforcing must be
provided. In Section 14.3 of the ACI Code, a minimum value of horizontal reinforcing
equal to 0.0025 of the area of the wall
bt
is required as well as a minimum amount of ver-
tical reinforcing (0.0015). These values may be reduced to 0.0020 and 0.0012 if the rein-
forcing is in. or less in diameter and if it consists of bars or welded wire fabric (not
larger than W31 or D31), with
f
y
equal to or greater than 60,000 psi.
The major changes in temperature occur on the front or exposed face of the stem. For
this reason most of the horizontal reinforcing (perhaps two-thirds) should be placed on
that face with just enough vertical steel used to support the horizontal bars. The concrete
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