Hi friends,

Great news before getting into today's topic: We will finally launch the e-book about loads of residential buildings next Wednesday (19.03.25). I got my VAT number yesterday and everything is set up. More info about price, what's included, etc. in the coming days.

Now to the topic of today.

On last week's newsletter, we learned how to calculate and design reinforced concrete columns by hand. Today, I'll show you how I actually design columns. → with software

Always keep in mind the formulas from Eurocode and other standards when using software. Without knowing them, you make very dangerous mistakes! And you probably wouldn't know what to input into the software.

But once you have done structural designs by hand a few times, you can and should use structural design software. Anything else is inefficient and time-demanding.

I am very happy and proud that ClearCalcs sponsors this episode of the Structural Basics newsletter.

As a Structural Basics reader, you also get a special deal. You get a 3-month free trial, instead of 1 month, if you sign up for a free trial by using the Structural Basics referral link: https://app.clearcalcs.com/?referralCode=2sGhr3a7c6rxKYhP&utm_source=structuralbasics&utm_medium=partnership&utm_campaign=newsletter-sponsorship​

This partnership is great, because I can show and teach you how to use structural design software.

In this newsletter, I’ll show you how to use the ClearCalcs concrete column calculator to design and verify reinforced concrete columns. We first, input geometry parameters like the cross-sectional dimensions, material parameters of the concrete and reinforcement and then loads. Finally, we check out the results and evaluate them.

Let's get into it..

1. Sign-up and open the Concrete Column Calculator

ClearCalcs is a web-based software, which makes it easier and faster to get started, because we don't need to install anything.

→ Sign up here and claim your 3-month free trial. ←

You can sign up with your Google or Microsoft account. Or if you don't want that, just with your e-mail.

Next, open the Concrete Column Calculator.

Once we are in the ClearCalcs project folder, click on Create a new project or if you already created a project for the beam analysis 4 weeks ago or the concrete beam analysis 2 weeks ago, you can also use that project.

If you create a new project, then fill out the project details (project name, project number, building standard → Eurocode for me) and click on Add a calculation. I already did this in the newsletter 2 weeks ago. You can fill out a project address if you want. This is beneficial if you design exterior walls, or roof rafters, because ClearCalcs automatically calculates the wind and snow loads based on the project address. For now, I just selected the address of the football stadium I used to play in.

Next, we click on Rectangular Concrete Column.

2. Properties of the column

First, we enter all the key properties of the beam such as cross-sectional dimensions, concrete strength, span, type and positions of the supports.

1. Depth and Width of Cross-Section: This is self-explanatory. In this tutorial, I use h=300mm as the cross-sectional height and b=300mm as the width.

2. Concrete Strength Class: When you click on this input field or click on Select, you can choose the concrete strength. C25/30 or C30/37 are most common for reinforced concrete columns.

3. Total Column Height: In this example, we'll use 4m =4000mm as the height/length.

4. Effective buckling lengths: The buckling length is dependent on the static system of the column. For simply supported columns the buckling length is the length of the column, for cantilever columns the buckling length is the length multiplied by 2. We have a simply supported column with 1 pinned supports and one roller. Therefore, the buckling length is 4m=4000mm in both directions.

5. Coefficient for Long Term Effects on Compressive Strength: This is a long-term factor, taking into account the reduction of the compressive concrete strength over time due to effects like creep and shrinkage. According to EN 1992-1-1 3.1.6 (1) Note the recommended value for α_cc=1.0. But, this value could be defined differently in the national annex.

6. Stress-Strain Relationship: You can choose between the Parabola Rectangle and the Bi-Linear relationship. According to EN 1992-1-1 3.1.7 you should use the parabola rectangle relationship unless you use a more conservative method like the bi-linear relationship. We use the Bi-Linear relationship.

7. Nominal Concrete Cover: The cover depends on the structural element, if it's exposed to water and what the fire demands are. We define it as 25 mm.

8. Partial and Reduction Factors of Concrete and Reinforcement: We use the partial factors from EN 1992-1-1 Table 2.1N. But these can be defined differently in your National Annex.

3. Reinforcement of the column

Next, we select the longitudinal and shear reinforcement of the column.

Longitudinal Reinforcement

1. Reinforcement Ductility Class: We use class B as the ductility class.

2. Reinforcement Type: Here, you select the diameter of the bottom reinforcement. For columns, this is the critical reinforcement to resist bending moments from wind loads or eccentricities. When you click on Select, you can choose all the different diameters. We use d=10mm.

3. Number of Reinforcement Bars: You can type in the number of top + bottom bars and the number of left and right bars. For squared columns, I always recommend using the same reinforcement on both sides. The guys on the construction site might make a mistake and put the reinforcement on the wrong side/edges. We want to make it as easy as possible for the construction companies. For rectangular columns, it makes more sense to have a different number of rebars in the long and short sides.

4. Bar Spacing Factor: EN 1992-1-1 8.2 (2) recommends k1 to be 1.0. But this value might be defined differently in your national annex. So please check that.

Transverse Shear Reinforcement

1. Reinforcement Ductility Class: We use class B as the ductility class.

2. Shear Reinforcement Type: This is the diameter of the shear reinforcement. We use d=8mm.

3. Link Spacing: This is the distances between the stirrups. We set it to 200mm.

4. Loads

Next, we'll apply loads on the column. We can apply vertical point loads and moments to the column.

1. Dead Load: In load type you select G which stands for dead loads, and then we define the vertical point load under Axial Load as 300 kN.

2. Occupancy: You can also change the name to live load under label. In load type you select Ql which stands for live loads, and then we define the vertical point load under Axial Load as 130 kN.

3. Building Category for Imposed Load: This is the live load category. It's important for the automatic load combination calculation. The different categories have different psi factors. The column is part of a residential building. We therefore set the category to A.

4. Location Category for Snow Load: In our example this isn't important as we didn't define a snow load. But if you design a column which is exposed to snow loads, then you need to select the location of your building as this influences the psi factor of the snow load for load combinations.

5. Self Weight: We select Yes.

5. Results of the reinforced concrete column analysis

ClearCalcs offers a wide range of calculation methods and verifications, which you can see in the picture below. ClearCalcs also documents calculation steps like the calculation of Load Combinations, Second Order Effects and the Design Moment Resistance. This is great for you to evaluate the results, and it makes it easier to find calculation mistakes. Many structural design software programs are a black box and only show the results - ClearCalcs is different.

For the verifications that ClearCalcs executes, you can see the utilization ratio on the side. In our example, that's ULS: Biaxial Bending (1.) with a utilization ratio of 85%. Additionally, you see all verification steps with descriptions when you click on it.

And then there is also the summary on the right side of the interface and at the very top. That's great when you are adding or removing reinforcement to quickly see if the column is still verified. It also shows the M-N diagram in y- and z-axis, which are interactive. Simply click on one of the diagrams and the values are shown.

6. Export as a PDF

As a structural engineer, you also need and want to document your calculations as PDF files.

And of course, we can also export the ClearCalcs calculations as a PDF. Simply click on the print button in the top right corner, select your Print Mode and Paper size of choice, and click on Export.

Final words

Now you have your first structural calculation report of a reinforced concrete column in PDF, which you can attach to your Structural Design report.

Let me know how you like ClearCalcs' concrete column designer. Or if it was the first time you used a structural design tool, let me know how much you like these tools instead of calculating with paper and pen. 😄

I hope you like these guides about how to use software in structural engineering. This is how structural engineers really do their work 80% of the time.

Thank you, ClearCalcs, for sponsoring this episode of the Structural Basics newsletter.

See you next Wednesday my friends.

Let’s design better structures together,

Laurin.

P.S.: In case you missed the ClearCalcs trial link, here’s another chance to claim your 3-month free trial and get started with structural design software today.

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