built-up beams

Guide to Design of Built-up Beams

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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.

Here are the simple steps that are to be followed for 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.

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Theory of Built-up Sections

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  • 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.

Built-up Section

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

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