Concrete pedestal design

[biro113]

I am designing a number of concrete plinths/pedestals (2m long X 0.3 X 1.3 h ) to support water tank (20000KG) mounted on top of existing slab.
Any guidance in terms of design considerations, minimum reinforcement and code detailing/embedment requirements?
It's not a wall neither can be considered as a column!

Many thanks

 

[Lion06]

I typically design piers as columns.

 

[TXStructural]

You will need to consider axial compression and flexure in both axis, because it really acts as a a laterally-loaded column. It is pinned at the top, so verify your fixity at the bottom...doweling into an existing slab may not provide much resistance to rotation at the base.

Minimum reinforcement will be as for other structural elements. Dowels from the slab will need to be designed similarly to ACI 318 Appendix D, however existing slab thickness and reinforcing could be an issue. I would consider either new foundations or making the new elements wider in the 0.3 m dimension, so that the overturning is resisted better by gravity loads, imposing less stress on the dowels into existing.

 

[JoshPlumSE]

A lot of people design pedestals as a vertical beam. It is actually a more conservative assumption to ignore the presence of axial compression.... at least as long as your axial force is low enough to keep you in the tensile failure portion of the interaction diagram.

Designing it as a beam makes all the calculations a bit easier. So, when I've got a pedestal with low axial load that is exactly what I do.