Figure 7-2.-Typical small footing.
Figure 7-3.-Reinforced concrete columns.
FOOTING AND FOOTING REINFORCE-
MENT. Footings support the entire structure
and distribute the load to the ground. The size
and shape of a footing depend upon the design
of the structure. In a small footing (fig. 7-2),
steel mats or reinforcements are generally
preassembled and placed after the forms have
been set. In large or continuous footings, such as
those found under bearing walls, steel mats are
constructed in place.
COLUMN AND COLUMN REINFORCE-
MENT. A column is a slender, vertical member
that carries a superimposed load. Concrete
columns, especially those subjected to bending
stresses, must always be reinforced with steel. A
PIER or PEDESTAL is a compressive member
that is short (usually the height is less than three
times the least lateral dimension) in relation to its
cross-sectional area and carries no bending stress.
In concrete columns, vertical reinforcement is
the principal reinforcement. However, a loaded
column shortens vertically and expands laterally;
hence, lateral reinforcements in the form of lateral
ties are used to restrain the expansion. Columns
reinforced in this manner are called tied columns
(fig. 7-3, view A). If the restraining reinforcement
is a continuous winding spiral that encircles the
core and longitudinal steel, the column is called
a spiral column (fig, 7-3, view B).
BEAM AND BEAM REINFORCE -
MENT. Beams are the principal load-carrying
horizontal members. They take the load directly
from the floor and carry it to the columns.
Concrete beams can either be cast in place or
precast and transported to the jobsite. Figure 7-4
shows several common types of beam reinforcing
steel shapes. Both straight and bent-up principal
Figure 7-4.-Typica1 shapes of reinforcing steel.