Wide-Flange Steel Shapes

Study Notes

Wide-flange shapes are structural steel beams with a wide, flat flange.
They are commonly used for beams and columns in buildings and bridges.
The "W" designation in steel designations indicates a wide-flange shape (e.g., W14x30).
The first number following the "W" (e.g., 14) indicates the nominal depth of the section in inches.
The second number (e.g., 30) gives the weight of the section in pounds per foot.
Wide flange sections provide high strength and stiffness for their weight.
The parallel flanges provide excellent resistance to bending.
They are efficient for resisting bending moments and shear forces.
Dimensions and properties such as area, moment of inertia, and section modulus are listed in steel manuals.
Common grades of steel used for wide-flange shapes are ASTM A36, A572, and A992.
A36 steel has a yield strength of 36 ksi (250 MPa).
A572 steel has various grades with yield strengths from 42 to 65 ksi (290 to 450 MPa).
A992 steel, commonly used for beams, has a minimum yield strength of 50 ksi (345 MPa).

I-sections, also known as standard beams or S-shapes, have a similar shape to wide-flange beams but with narrower flanges.
The inner surfaces of the flanges are sloped.
They are designated with an "S" (e.g., S12x50).
The first number following the "S" indicates the depth of the section in inches.
The second number gives the weight of the section in pounds per foot.
S-shapes are less efficient than wide-flange beams for bending resistance.
They are often used in older structures or applications where their specific dimensions are required.
Similar to wide-flange beams, the dimensions and properties of S-shapes are detailed in steel manuals.
Common grades of steel used for I-sections include ASTM A36.

Angle bars, also known as angles, are L-shaped structural steel members.
They are designated with an "L" (e.g., L3x3x1/4).
The designation gives the length of each leg and the thickness of the legs.
For example, L3x3x1/4 indicates an angle with legs 3 inches long and 1/4 inch thick.
Angles are used as connection elements, web members in trusses, and bracing.
They can be oriented with equal legs or unequal legs.
Unequal leg angles provide different bending properties about different axes.
Angle bars are commonly made from ASTM A36 steel.
They are joined by bolting or welding.
The design strength of angles depends on the limit states of yielding, fracture, and block shear.

Flat plates are rectangular steel members with a uniform thickness.
They are designated by their width and thickness (e.g., PL1/2x6).
This example indicates a plate with a thickness of 1/2 inch and a width of 6 inches.
Plates are used for a variety of purposes, including:
Connection plates in steel structures
Base plates for columns
Stiffeners for beams and columns
Plates are typically made from ASTM A36 steel.
They are connected to other members by welding or bolting.
The design of plates involves consideration of:
Tension
Compression
Shear
Bending stresses depending on the application.
Buckling can be a concern for plates subjected to compressive stresses.

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