## Guide to Design of Built-up Beams

#### Design Procedure of the Built-up Beams design

In my earlier articles, we discussed in detail about the “Theory of Built-up Beams“. In this article, we will move a step ahead and understand the concept of the design of Built-up beams.

#### Step one

The effective span and load required to be carried by the built-up beam are known.

Maximum bending moment and shear force in built-up beams are calculated.

#### Step two

Value of yield stress (fy) for structural steel is to be assumed.

The permissible bending stress (sigma bc) is calculated.

#### Step three

The required section modulus (Z) for the given beam section is calculated.

## Theory of Built-up Sections

• A built-up beam is also known as compound beam.
• The built-up beams are used when the span, load and corresponding bending moment are of such magnitudes that rolled steel beam section becomes inadequate to provide required section modulus.
• Built-up beams are also used when rolled steel beams are inadequate for limited depth.
• In building construction, the depth of beam is limited by a space provided by the architect.
• Drawing beam of small depth do not provide required section modulus. Therefore, plates are attached to the beams.
• The strength of rolled steel beams is increased by adding plates to its flange which is one of the method forming built-in section.
• The other method is to compound a number of rolled steel sections themselves.

The built-up sections shown in figure’ A’ and ‘B’ are used for heavy loads and small spans.