## Concrete slabs on grade-theory of length to width ratio limit?

## Concrete slabs on grade-theory of length to width ratio limit?

(OP)

Hi to all,

I'm wondering what's the theory behind limiting the length to width ratio between joints in a slab on grade?

It's widely known that the ratio of panel length to width shouldn't exceed 1.5. Panels with excessive length to width ratios are likely to crack at the mid-panel point or at some other location between joints. But from where this number came from?

Thank you for all comments in advance

Take care

I'm wondering what's the theory behind limiting the length to width ratio between joints in a slab on grade?

It's widely known that the ratio of panel length to width shouldn't exceed 1.5. Panels with excessive length to width ratios are likely to crack at the mid-panel point or at some other location between joints. But from where this number came from?

Thank you for all comments in advance

Take care

## RE: Concrete slabs on grade-theory of length to width ratio limit?

## RE: Concrete slabs on grade-theory of length to width ratio limit?

## RE: Concrete slabs on grade-theory of length to width ratio limit?

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-Dik

## RE: Concrete slabs on grade-theory of length to width ratio limit?

That theory is basically just the theory of elasticity in the context of shrinkage induced tensile strain. When panel aspect ratios drift too far from unity, the ability of the the jointing to absorb strain around the perimeter loses it's two way character and effectively become a less efficient one way system.

I like to imagine three equal area trampolines where the mat is a bit old and crusty and I'm trying to prevent a tear. You have to imagine stiff diaphragm shear restraint around the perimeter to make the analogy work. No doubt the 1.50 value that we use is very approximate and experience based rather than calculated.

## RE: Concrete slabs on grade-theory of length to width ratio limit?