Structural Elements

Ties

Ties are structural members that are only subject to axial tension, and no other forces [2]. Load is only applied at the ends of the tie, and they are not designed to withstand any bending forces on the member. Ties are most commonly found in the sloped roof of residential housing buildings.

Struts

Struts are similar but opposite to ties [2]. Struts can also only be loaded at their ends, and cannot withstand bending forces. Unlike ties, however, struts are subjected only to axial compression forces. Similar to ties, struts are also commonly found in the structure of sloped roofs. 

Beams

Beams are members which are primarily subject to bending forces along the length of the member [2]. Beams are usually horizontal members which primarily withstand gravity forces. Beams are more commonly seen in industrial or commercial building which have more of a rectangular shape. 

Columns

Columns are members primarily subjected to axial compression forces, but can also withstand bending forces [2]. Columns are almost always vertical elements which interlace with grids of beams. Columns are also mostly found in industrial or commercial buildings. 

Diaphragms

Diaphragms are flat plate elements. Diaphragms are generally used as floors, or when stiffness is required in walls [2]. Diaphragms span or connect beams and columns. Diaphragms are found in almost every type of structure as they take the shape of floors or walls. 

Beams are characterized by the following dimensions, shown on the diagram to the right:

• • • h: Depth of Section
    • w: Flange Width
    • s: Web Thickness

Other dimensions of I-Beams include:

• • • Flange Thickness
    • Root Radius (Radius of the chamfer)

There are a variety of different types of I-beams, such as wide flange, and tapered flange. 

For a full table of dimensions and parameters for I-Beams, see https://www.engineeringtoolbox.com/i-flange-steel-beams-d_1317.html 

Different beam types can also be located on Engineering Toolbox.

C-Channels are characterized by the same dimensions as I-Beams, shown on the diagram to the right:

• • • h: Depth of Section
    • w: Flange Width
    • s: Web Thickness

For a full table of dimensions and parameters for C-Channels, see https://www.engineeringtoolbox.com/american-standard-steel-channels-d_1321.html

Angle Channels are characterized by the Depth and Thickness Dimensions, shown on the right:

• • • h: Depth of Section
    • s: Thickness

Some channels may not have equal leg lengths, these channels are called unequal angle channels and can also be located on Engineering Toolbox.

For a full table of dimensions and parameters for Equal Angle Channels, see https://www.engineeringtoolbox.com/steel-angles-d_1324.html

Area Moment of Inertia of Beams 

Area Moment of Inertia is a key property to consider when looking at beams. It is a property of a beam's cross-section that describes bending, deflection, and stress that occurs in that beam. The higher the moment of inertia of the beam's cross-section, the less the beam will bend. Area moment of inertia can be calculated on both the y and x axis, with I_x denoting that the object is bending along the x axis. Because of this, the x-axis value is the important value as that is the direction that resists vertical load. 

Area Moment of Inertia can be calculated using a formula, however the formula varies depending on the shape of the cross section. A few of the common formulas are shown below. It is also common for suppliers to list the value alongside the specific beam dimensions.

• • • Rectangular: I_x = b h³ / 12 ; I_y = b³ h / 12 ; where b is the width, and h is the height on the rectangle. 
    • Solid Circular: I = π r⁴ / 4 = π d⁴ / 64   ; where r is the radius of the circle
    • Hollow Circular: I = π (d_o⁴ - d_i⁴) / 64 ; where d_o is the outer diameter, and d_i is the inner diameter 
    • I-Beam: I_x = (a h³ / 12) + (b / 12) (H³ - h³) ; I_y = (a³ h / 12) + (b³ / 12) (H - h)