Hi Reader

A new mezzanine I was designing has about 54 kN coming down one of the new steel columns onto an existing warehouse slab.

The easy solution would be to cut the slab and add a new footing.

But before creating all that extra work, I wanted to see if the existing slab could do the job.

I started by working backwards from the column reaction.

Assuming 100 kPa allowable bearing pressure:

Required area = 0.31 m² ≈ 560 × 560 mm

Then the question becomes whether the existing slab can spread the load from the smaller base plate out to that effective area.

So I checked the slab for bending, one-way shear and punching shear.

It worked.

But because this is an existing structure and I’m relying on a simplified model, I also cross-checked the result using the CCAA T48 industrial floor approach.

Different method. Same question. Similar result.

I think this is one of the more interesting parts of structural engineering.

The equations themselves are often pretty simple. The harder part is deciding what needs to be checked, what assumptions you can rely on, and what needs to be verified on site.

That’s also why I’ve just added a new course inside BengLab called Inside the Design Office.

Instead of isolated calculations, I’ll take you through real projects and show how the whole design comes together.

The first walkthrough is this mezzanine extension inside an existing tilt-up panel warehouse, including the framing decisions, existing steel checks, vibration, new beams and columns, and the slab/footing check above.

If you’re already a member, you’ll find it in the BengLab Classroom under Inside the Design Office.

If you’re not a member yet, you can join here: https://www.skool.com/benglab/about​

Cheers,

Gabe