Structural steel

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Structural steel is one of the basic materials commonly used in structures, such as industrial and commercial buildings, bridges, and piers. It is produced in a wide range of shapes and grades, which permits great flexibility in its usage. It is relatively inexpensive to manufacture and is the strongest and most versatile material available to the construction industry. This

Figure 1-32.—Structural steel shapes and designations.

terminology applied to structural steel members, the use of these members, and the methods by which they are connected.


Structural steel is manufactured in a wide variety of cross-sectional shapes and sizes. Figure 1-32 shows many of these various shapes.

Figure 1-33 shows cross-sectional views of the W-shape (wide flange), the S-shape (American Standard I-beam), and the C-shape (American Standard channel). The W-shape is the most widely used structural member for beams, columns, and other load-bearing applications. As seen in the figure, it has parallel inner and outer flange surfaces that are of constant thickness. This flange design provides greater cross-sectional area in the flanges, which results in greater strength than is provided by the S-shape, which has a slope of approximately 17 degrees on the inner flange surfaces. The C-shape is similar to the S-shape in that its inner flange surface is also sloped approximately 17 degrees. The C-shape is especially useful in locations section describes structural steel shapes, the

Figure 1-33.—Structural shapes.

where a single flat surface on one side is required. When used alone, the C-shape is not very efficient as a beam or column. However, efficient built-up members maybe constructed of charnels assembled together with other structural shapes and connected by rivets or welds. The W-, S-, and C-shape structural members are designated by their nominal depth, in inches, along the

Figure 1-34.—Angles.

Figure 1-35.—Built-up column section.

web and the weight, in pounds, per foot of length. A W14 x 30, for example, indicates a W-shape that is 14 inches deep along its web and weighs 30 pounds per linear foot. Hence a 20-foot length of this size W-shape would weigh a total of 600 pounds.

The bearing pile, HP-shape, is almost identical to the W-shape. The only difference is the thickness of the web and flange. In the bearing pile, the web and flange thickness are equal, whereas the W-shape has unequal web and flange thickness.

An angle is a structural shape whose cross section resembles the letter L. As pictured in figure 1-34, angles are available with either equal or unequal legs. The dimension and thickness of its legs are used to identify an angle; for example, L6 x 4 x 1/2. The dimension of each leg is measured along the outside of the angle, and for unequal-leg angles, the dimension of the wider leg is always given first, as in the example just cited. The third dimension applies to the thickness of the legs, which always have equal thickness. Angles are used primarily to support, brace, or connect other structural members. They may be used as single members, or they may be used in combinations of two or four to form main members.

Steel plate is a structural member that has a width greater than 8 inches and a thickness of 1/4 inch or more. Plates are generally used as connections between other structural members. They may also be used as

Figure 1-36.—Weight and thickness of steel plate.

Figure 1-37.—Bars.

component parts of built-up structural members, such as the built-up column shown in figure 1-35. Plates cut to specific sizes may be obtained in widths ranging from 8 inches to 120 inches or more and in various thicknesses.

Plates are identified by their thickness, width, and length, all measured in inches; for example, PL 1/2 x 18 x 30. Sometimes, you may also hear plate referred to by its approximate weight per square foot for a specified thickness. As shown in figure 1-36, 1 cubic foot of steel weighs 490 pounds. This weight divided by 12 gives you 40.8 pounds, which is the weight of a steel plate measuring 1 foot square and 1 inch thick. By dropping the fractional portion, a 1-inch plate is called a 40-pound plate; and, with similar reasoning, a 1/2-inch plate is called a 20-pound plate.

The structural shape referred to a bar has a width of 8 inches or less and a thickness greater than 3/16 inch. The edges of bars usually are rolled square, like universal mill plates. The dimensions are expressed in a similar manner as that for plates; for instance, bar 6 x 1/2. Bars are available in a variety of cross-sectional shapes-round, hexagonal, octagonal, square, and flat. Three different shapes are shown in figure 1-37. Both squares and rounds are commonly used as bracing members of light structures. Their dimensions, in 

Figure 1-38.—Structural steel skeleton construction. 

inches, apply to the side of the square or the diameter of the round.


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