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Figure 1-48.—Types or welds. |
information regarding the PEB, you should refer to the
current Steelworker TRAMAN.
STRUCTURAL STEEL CONNECTORS
There are four basic connectors used in making
structural steel connections. They are bolts, welds, pins,
and rivets. Bolts and welds are the most common
connectors used in military construction. Pins are used
for connections at the ends of bracing rods and various
support members that require freedom of rotation.
Commercial prefabricated steel assemblies may be
received in the field with riveted conectors. Types and
uses of the four basic connectors are discussed in the
following text.
Bolts
Bolts are used more than any other type of
connectors. They are easy to use and, in contrast to all
other types of connectors, require little special
equipment. The development of higher strength steels
and improved manufacturing processes have resulted in
the production of bolts that will produce strong
structural steel connections.
Specifications for most bolted structural joints call
for the use of high-strength steel bolts tightened to a high
tension. The bolts are used in holes slightly larger than
the nominal bolt size. Joints that are required to resist
shear between connected parts are designated as either
friction-type or bearing-type connectors.
Bolted parts should fit solidly together when they
are assembled and should NOT be separated by gaskets
or any other type of compressible material. Holes should
be a nominal diameter, not more that 1/16 inch in excess
of the nominal bolt diameter. When the bolted parts are
assembled, all joint surfaces should be free of scale,
burrs, dirt, and other foreign material. Contact surfaces
with friction-type joints must be free of oil, paint, or
other coatings.
Welds
Welding is a highly specialized skill, and welding
of load-bearing parts of a structure should be performed
only by properly qualified personnel. As an EA, you will
not be expected to perform welding operations.
However, you should have a general knowledge of the
principal welding processes and the different types of
welds and their applications, and you should know how
welding symbols are used to identify welded
connections shown in working drawings.
The two principal welding processes used in
structural work are electric arc welding and oxy-MAPP
gas welding. In the electric arc welding process, welding
heat, sufficient to fuse the metal together, is developed
by an electric arc formed between a suitable electrode
(welding rod) and the base metal (the metal of the parts
being welded). In the oxy-MAPP gas welding process,
heat is obtained by burning a mixture of MAPP gas and
oxygen as it is discharged from a torch designed for this
purpose. While electric arc welding is normally used for
metals that are 1/8 inch or larger in thickness,
oxy-MAPP gas welding is usually restricted to thinner
metals.
The principal types of welds and welded joints that
are suitable for structural work are shown in figures 1-48
and 1-49.
On drawings, special symbols are used to show the
kinds of welds to be used for welded connections. These
symbols have been standardized by the American
Welding Society (AWS). You should become familiar
with the basic welding symbols and with the standard
location of all elements of a welding symbol.
The distinction between a weld symbol and a
welding symbol should be noted. A weld symbol is a
basic symbol used to indicate the type of weld. Basic
weld symbols are shown at the top of figure 1-50. The
supplementary symbols shown in the figure are used
when necessary in connection with the basic weld
symbols.
A welding symbol consists of the following eight
elements, or as many of these elements as are required:
(1) reference line, (2) arrow, (3) basic weld symbol,
(4) dimensions and other data, (5) supplementary
symbols, (6) finish symbols, (7) tail, and (8) specifica-
tion, process, or other reference. These elements of the
welding symbol have specific standard locations with
respect to each other, as shown in figure 1-50. When a
finish symbol is used in a welding symbol, it indicates
the method of finish, not the degree of finish. For
example, a C is used to indicate finish by chipping, an
M indicates machining, and a G indicates grinding.
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