Home » How to calculate the design capacity of a steel column? [Step by Step guide]

# How to calculate the design capacity of a steel column? [Step by Step guide]

## What is a steel column?

A structural member made of steel which primarily resist load in compression is a steel column. It may transfer loads from beams, ceilings, floor slabs, or roof slabs to floors or foundations.   Additionally, bending moments along cross-section axes may be present in steel columns.

Note: If there are bending moments acting on the column, it is called beam column.

Learn more: how to design of beam columns?

## Design guidelines for column design

Guidelines to calculate design capacity of columns are given in almost every building code around the world. Essentially all the codes follow the similar design philosophy with variations in the approach of design.

We will cover the design according to the American national standard ANSI/AISC 360-16 Specification for Structural Steel Buildings

## Design Philosophy for Steel columns

Design of any structural member including steel columns is governed by its limit states (or failure criteria). Limit states can be simply interpreted as all the possible failure mechanism that can appear in a structural member. Three limit states primarily characterize the behavior of steel columns.

• Yielding in compression
• Global buckling
• Local buckling

The least strength corresponding to any limit state will govern the design capacity of the column

## Design strength of steel column corresponding to different limit states

Steel column Yielding in compression

Steel column buckling (local/global)

## How to calculate the design capacity of a steel column?

Use following design flow chart to calculate the design capacity of a steel column.

You would be needing two documents before hand to calculate the design capacity of a steel column

Steps to compute the design capacity of a steel column

• Step 1: Gather information on column geometry
• Step 2: Classify all cross section elements as slender or non slender
• Step 3: Calculate Elastic critical stress (Fex or Fey or Fe)
• Step 4: calculate Critical stress (Fcr)
• Step 5: Calculate Ae or use Ag
• Step 6: Calculate Pn
• Step 7: Compared Pn with ultimate or allowable load to verify the design capacity