Hi friends,

Today I want to show you a bracing system of a steel staircase which wasn't designed very well.

I was the checking engineer of the project. In Germany there is a second engineering office for most projects checking the structural design / calculations.

But the checking engineer only has to check the ULS verifications to make sure that the structure dosn't collapse. SLS checks such as deflections are not part of it.

In the following pictures you can see that the columns are deflected horizontally. This happened during tensioning of the wind braces because the columns are not held horizontally by a support or a compression member.

Here's the static system explaining the horiontal deflection of the columns.

Now in this case the deflection wasn't critical as the columns only had a utilisation ratio of 10-20% and they could still take up the additional imperfection loads. But a deflection like this doesn't look nice and it's not what the client paid for.

We did our job correctly and we put the pictures into our report. The structural engineer who did the design was responsible for the deflection.

How to avoid the horizontal deflection?

You can avoid the horizontal deflection by adding a compression member. Rectangular hollow profiles are most common for this.

Another way to do it is to connect the steel braces to the supports.

Images help explain structural design to architects

Last week I send my sketches of a steel staircase to the architect. I connected the wind braces to supports at the foundation. One of their questions was if it's possible to connect the wind braces to the columns 0.5m above the foundation.

I responded with: Yes, sure we can do that, but then the columns will deflect horizontally once the wind braces get tensioned like in the pictures attached. If we add a compression member the columns won't deflect. Please let me know if you want to

• keep my original design
• move the wind braces upwards 0.5m and don't add a compression member or
• move the wind braces upwards 0.5m and add a compression member

He responded with: "Oh wow, the deflection looks horrible, we want the compression member."

He would have never understood why a compression member makes sense without the images.

The images changed that and it even underlined my competence, because he understood it himself as well.

Final Words

Today's newsletter was a bit different as I showed you a real world engineering example.

I hope you learned something from it. These examples are exactly what I was missing during my studies as you learn these things once you gain some experience as a structural engineer.

Anyway, let me know if you like today's newsletter and if you want to see more of these examples. Just respond to this newsletter.

Enjoy the rest of the week and your weekend.

I’ll see you in the next newsletter.

Let’s design better structures together,

Laurin.

P.S. Whenever you're ready, here's one more resource to learn structural engineering:

I teach you everything you need to know about load calculation. It's the most important fundamental of structural engineering. ​Without knowing your loads you can't design your structural elements. Click → here ← to learn.​

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