Beam Analogy (Approximate) method

In this method, the internal forces are found assuming the elongated truss is a beam.

For a simply supported beam

• Maximum bending moment is at mid-span:
• Maximum shear force is at the supports:

Here:

• Chord members - horizontal members
• Web members - diagonal members
• - truss depth

In the truss,

• Bending moment is carried by chord members.
  
• Shear force is carried by vertical component of web member force

Pratt & Howe type trusses

Pratt type truss is shown below.

Internal force in web members are tensile.

Howe type truss is a shown below.

Internal force in web members are compressive.

Usually Pratt type is cost-efficient. To make sure a howe type truss is strong enough like pratt type, web members must be shorter and thicker.