STEEL - Materials for Civil and Construction Engineers - page 99

FIGURE 3.8 Structural steel used to make columns, beams, and floors for the
structural support of a building.
generally an A for ferrous materials, followed by an arbitrary serially as-
signed number. For example, ASTM A7 was a specification for structural
steel written in 1900 and ASTM A992 was published in 1999 (Carter, 2004).
The designation or specification number does not contain any meaningful in-
formation other than to serve as a reference. Within ASTM specifications, the
terms grade, type , and class are used in an inconsistent manner. In some
ASTM steel specifications, the term grade identifies the yield strength, while
in other specifications, the term grade can indicate requirements for both
chemical compositions and mechanical properties. ASTM and SAE have de-
veloped the Unified Numbering System, UNS (ASTM E527), based on chem-
ical composition. This system uses a letter to identify the broad class of
alloys, and a five-digit number to define specific alloys within the class.
Several grades of structural steel are produced in the United States.
Table 3.2 is a summary of selected information from various sources. The
American Institute of Steel Construction, AISC, Manual for Steel Construc-
tion is an excellent reference on the types of steel used for structural appli-
cations. However, the best sources of information for structural steels are the
various ASTM specifications. Of particular note is the fact that additional
requirements are frequently included, dependent on the geometry of the
product made with a particular steel.
Historically, dating back to 1900, only two types of structural steel were
used in the United States: A7 for bridges and A9 for buildings. The specifica-
tions for these materials were very similar and in 1938, they were combined