## 20 Kip Point Load over a 7' Square Concrete Slab

## 20 Kip Point Load over a 7' Square Concrete Slab

(OP)

Do anyone has the formula for a point load on a simply supported slab using the "theory of elasticity". AASHTO has a very simple formula but it is around 25% conservative. Essentially there are both torsional moments and bending moments that resist the point load. The crossing beam analogy is the simplest most conservative way to determine the moments in both directions. Any tips will be greatly appreciated.

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

This is based on a simplified 2 way distribution of the load.

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

I agree with EIT and get around 260 psi using Roarke and another method. For a bending moment, I get a peak moment of 4.4 k'/ft. The 17.5 k' is a average over the entire width of the plate.

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

I agree with the 260psi but I disagree with the 4.4k-ft/ft.

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

AASHTO E = 4 + 0.06(S) or E = 4.42ft as the effective width

Using 10k/4.42' = 2.26K Load. PL/4 = 3.95k-ft/ft

Does this really apply to a 7' x 7' area??

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

I don't believe the AASHTO provision (3.24.3.2) is really meant for two way slabs. I think it is meant for one way slabs with the supporting stringers perpendicular to the direction of traffic. That said, I think it can give a close enough approximation the way you use it. We only differ here by 10%, 4.4 k'/ft vs 3.95 k'/ft. I have one other reference that gives 4.4 k`/ft and another (Seeley & Smith Advanced Mechanics of Materials Article 74) that gives 3.6 k'/ft.

## RE: 20 Kip Point Load over a 7' Square Concrete Slab

Thanks Alot. Done Deal.