STEEL - Materials for Civil and Construction Engineers - page 101

into a single specification, A7. The specification for A7 and A9 were limit-
ed to requirements for the tensile strength and yield point only; there were
no chemical specifications. The chemical composition, particularly carbon
content, became an issue during the 1950s, as welding gained favor for mak-
ing structural connections. By 1964, AISC adopted five grades of steel for
structural applications. The 1999 AISC Load and Resistance Factor Design
Specification for Structural Steel Buildings, 1999, identifies 15 different
ASTM steel designations for structural applications.

■ Sectional Shapes

Figure 3.9 illustrates structural cross-sectional shapes commonly used in
structural applications. These shapes are produced in different sizes and are
designated with the letters W, HP, M, S, C, MC, and L. W shapes are doubly
symmetric wide-flange shapes whose flanges are substantially parallel. HP
shapes are also wide-flange shapes whose flanges and webs are of the same
nominal thickness and whose depth and width are essentially the same. The
S shapes are doubly symmetric shapes whose inside flange surfaces have ap-
proximately 16.67% slope. The M shapes are doubly symmetric shapes that
cannot be classified as W, S, or HP shapes. C shapes are channels with in-
side flange surfaces having a slope of approximately 16.67%. MC shapes are
channels that cannot be classified as C shapes. L shapes are angle shapes
with either equal or unequal legs. In addition to these shapes, other struc-
tural sections are available, such as tee, sheet piling, and rail, as shown in
Figure 3.9.

3.5.2

(a) (b) (c)

(d) (e)

(f) (g) (h)

FIGURE 3.9 Shapes commonly used in structural applica-
tions: (a) wide-flange (W, HP, and M shapes), (b) I-beam
(S shape), (c) channel (C and MC shapes), (d) equal-legs angle
(L shape), (e) unequal-legs angle (L shape), (f) tee, (g) sheet
piling, and (h) rail.