Reinforced vs. un-reinforced slab-on-grade deflection

[W.G.Khoury]

thread507-401939

Dears,

Can anyone help me answer the following questions?

1) Does a reinforced slab-on-grade have a different deflection under a point load than a similar slab-on-grade that differs only by being unreinforced?

2) If it does differ, how can I approximate the deflection of a reinforced slab-on-grade under a point load action?

Thanks in advance for your help.

Wissam

 

[jayrod12]

The "deflection" of a grade supported slab has almost everything to do with the base preparation. It's not deflection however, it would be classified more as settlement. I'd ask a geotechnical engineer for more information.

 

[BAretired]

1) Does a reinforced slab-on-grade have a different deflection under a point load than a similar slab-on-grade that differs only by being unreinforced?

Probably not enough difference to notice, provided the slab does not crack as a result of the load or has not cracked in the vicinity of the load as a result of temperature or shrinkage effects. If the slab has cracked, deflection would be difficult to predict.

Unreinforced slabs have been used in airstrips, but they are very thick and have many joints to prevent cracks from occurring.

2) If it does differ, how can I approximate the deflection of a reinforced slab-on-grade under a point load action?

Not an easy question to answer without making some assumptions about the soil, the position of the load and the magnitude of the load.

The following may be helpful:

https://structurepoint.org/publication/pdf/Unreinforced Plain Slabs on Grade.pdf

BA

 

[STrctPono]

So as not to convolute my answer with too much extraneous information, the short answer is NO. There will not be a difference between a reinforced and an unreinforced slab on grade in terms of "deflection." Pavement or slab-on-grade design includes three components: The slab, the base course, and the sub grade. All three need to be considered acting together as they are a system.

 

[r13]

Effect of reinforcing steel is normally ignored in determining concrete beam deflection; you should use beam on elastic foundation solution. Consult with your geotech for subgrade parameters, or make your own assumptions.