Steel Column Design

All The Steps You Need To Follow

Hi friends, ✌️✌️

After weeks of content about timber, it’s finally time to look at a different material.

Today, we’ll look at all the calculation steps required to design a steel column according to Eurocode.

This will give you an overview. If you want to dive deeper into the formulas, then check out our step-by-step article. ✍️✍️

Here are the steps:

1. Calculation of characteristic loads (dead, live, snow and wind load)

2. Set up load combinations

3. Pick a steel cross-section and set up the geometric and material properties

4. Classify the cross-section

5. Compression verification

6. Bending verification (in case it’s a column on the facade, and it’s taking up wind loads)

7. Flexural buckling verification

Alright, let’s dive into it. 🚀🚀

#1 Characteristic loads

We’ve written detailed articles about loads, which you can follow to understand how to calculate these loads:

• Wind load on flat roof

• Wind load on walls

• Snow load on flat roof

• Dead load

• Live load

#2 Load combinations

Load combinations combine the characteristic loads and add safety factors.

→ Detailed guide to load combinations ←

#3 Steel cross-section & geometric and material properties

Material

You choose the steel material and define the material properties such as E-modulus, tensile strength, etc. You can choose between the following strength classes:

• S235

• S275

• S355

• S450

These are at least the most common types in Denmark. From my experience for normal structures S235 and S355 are commonly used.

The number stands for the steel yield strength.

Cross-section

There are plenty of steel cross-sections, just google a bit to find +10 commonly used section. For typical building structures, HEB, HEA, SHS and RHS are mostly used for columns.

Here are 2 great tools where you can find all the data for the different cross-sections:

• Eurocode Applied

• Dlubal Cross-Section properties

#4 Cross-section classification

Steel cross-sections have to be classified in order to find out if the specific element can be calculated with plastic or elastic analysis.

Now, for the typical building steel column, the cross-section is classified as class 1. However, I recommend that you check out the detailed calculation according to Eurocode in our article.

#4 Compression verification

First, we find the design axial force acting on the column. How you find this load in a big building is a topic for another time. But we found the biggest design load as

Then, we calculate the compressive design resistance force (EN 1993-1-1 (6.10)):

Finally, we check the utilization.

#5 Flexural buckling about y-axis

First of all, we need to know which static system we are using. Different static systems have a big influence on the buckling resistance of a column. We use a simply supported column with a buckling length of:

Slenderness (EN 1993-1-1 6.3.1.3 (1)):

Non-dimensional slenderness (EN 1993-1-1 (6.50)):

Buckling reduction factors (EN 1993-1-1 (6.49)):

Design buckling resistance around the y-axis (EN 1993-1-1 (6.47)):

And finally checking the utilization:

#6 Flexural buckling about z-axis

Now, this is basically the same calculation as #5. The buckling length could be different if you use a different static system out of plane and the moment inertia is different, which you use to calculate the non-dimensional slenderness. But if you want to see all the steps, then read up in our article. 📖📖

If #6 verifies, our steel column is designed. ✅💪

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Conclusion

Designing steel columns exposed to only axial loads is pretty straightforward. We classify the cross-section, verify compression and buckling.

However, often columns are also exposed to lateral loads like wind loads. In that case, we also need to verify the column for bending.

See you next week for another structural guide.

Cheers,

Laurin. ✌️✌️