Continuous Slab Design - Irregular Spans?

[Redacted]

Hi there,

I'm working on a project where I need to design the slab for a new floor. See the image below, the new upper suspended slab footprint is shown in blue:

For a situation like this, where there are a mix of one way and two way spanning slabs that will all be poured monolithically, I'll end up with a few locations where the slabs are continuous over either a wall or a beam.

In most books I have looked in, there are coefficients for continuous slabs but they tend to be only applicable when the span lengths are the same.

In a situation like this, where there are different span lengths and different slab types, how should I go about the analysis?

As the entire floor will likely be poured monolithically, this will result in continuous slabs, however, should I be looking at each slab panel independently? E.G. For Slab 1, design it as a slab panel supported on 4 sides and assume the continuous side (between Slab 1 and Slab 2) as fixed and the rest simply supported? Then do the same for Slab 2, design it as supported on 4 sides and assume the continuous sides as fixed. And whichever has the highest hogging moment out of Slab 1 and 2 use that as the top reinforcement; extending the top reinforcement 1/3 the slab length for Slabs 1 and 2?

And then use the same approach for the rest of the slabs?

Any assistance would be helpful on how this is usually done or how it should be done.

 

[sdz]

Last century this is something we would routinely do by hand, so maybe find an old guy who can help.

Of course there are design packages these days that could do much of the design for you (e.g. Inducta) but I assume you don't want to shell out for one of those.
There are design by coefficient tables/diagrams available and these usually include an allowance for the spans not being equal. These tend to be somewhat conservative. (E.g AS3600:2018 - 6.10 see attachment)
You could use Hillerborg's strip method of design. (I recommend you read it anyway)
You could use yield line analysis.

 

[HTURKAK]

My suggestion would be , look to the applicable code in your region. The modelling and design could be,

- With moment coefficients ( using similar table proposed by sdz (Structural)) . In this case , the dissimilar moments at common supports need to be redistributed . The slab panel S4 will experience negative moment at midspan.
- The use of unit strips ( S3-S4 ) and (S1 -S2 )
- Modelling the panels with FEM .



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