called a key, is built into spread footings to
indicated symbolically on drawings, but its thickness
strengthen the bond between footings and walls that
is noted.
are poured later.
When heavily loaded
f. Bearing Plates.
b. Construction Joints. Construction joints
beams or columns bear on masonry or concrete
are divisions between concrete work performed at
supporting members, metal plates are used to
periods far enough apart to allow partial hardening.
distribute the load and prevent crushing the surface of
For horizontal work, such as floor slabs, construction
the supporting member. The plates are made of steel
joints should be in a vertical plane. For vertical
or cast iron and may be held in place by grout,
work, such as columns, the joints should lie in a
dowels, anchor bolts, or the weight of the supported
horizontal plane. Although construction joints have
member.
no permanent function but to represent a convenient
stopping place, they affect the strength of the
(1) Beam supports. Bearing plates are
structure. Their location is indicated in a drawing
used to distribute the loads of horizontal members
with a heavy, unbroken line and the note "permissible
bearing on masonry walls. Usually these plates are
construction joint" or "construction joint."
of a simple rectangular shape.
(2) Column supports. Base plates are
c. Construction and Expansion Joints.
Concrete usually contracts while hardening and
used to distribute the loads of columns bearing on
expands after it has hardened because of changes in
concrete or masonry piers and footings and may be
atmospheric temperature. To provide for the changes
plain or ribbed. Base plates for pipe columns may
in volume that occur at these times, it is necessary to
have a vertical projection or dowel to fit inside the
supply joints at frequent intervals.
column to hold the column in place.
(1) Contraction joints. Various designs of
g. Anchor Bolts. Anchor bolts are the most
contraction joints are used. In all cases, however,
frequently used means of connecting wood and steel
they represent a clean break between the two
to concrete (fig 2-17). The end embedded in the
sections. No reinforcing extends across the break,
concrete is hooked to provide a stronger bond.
which should be filled with an elastic joint filler or
Anchor bolt dimensions are given in specific notes
protected in some other way. Joint details are shown
and state diameter and length. For example, the note
in a detail drawing.
"1/2 x 1' -2" anchor bolts at 4' -8" OC" means that the
bolts are 1/2 inch in diameter; 1 foot, 2 inches long,
(2) Expansion joints. Expansion joints are
and are spaced at intervals of 4 feet, 8 inches
required wherever expansion might cause a concrete
measured on centers around the perimeter of the
slab to buckle. Mastic joints are commonly used to
foundation wall.
separate sections from each other, thus allowing
room for expansion.
2-16. MASONRY CONSTRUCTION
d. Masonry Units. Masonry units, such as
Bricks, hollow clay tiles, concrete or cinder
brick, structural tile, and cinder block, are bonded to
blocks, concrete tiles, and stone are used in various
foundation walls with mortar. Metal ties may be
combinations in masonry construction. The sizes,
added to increase the strength of the bond.
shapes, and characteristics of masonry units
determine their applicability and use in construction.
e. Grout. Grout is a mixture of cement, sand,
The specified type and placement of masonry units
and water. Grouting is the process of adding a layer
are shown in plans of masonry structures.
of concrete to concrete that has been poured
previously. It is frequently used to bring bearing
a. Brick Types. Brick types are determined by
surfaces, such as column footings and foundation
size, shape, and usage. Figure 2-23 shows the
walls, to the exact grade desired. Grout is not
various brick cuts and masonry joints.
67
Previous Page
