Thickened Edge Slab Analysis

[Brad805]

I was asked for a small thickened edge slab design, and I decided to look at this a bit closer than some times in the past. I found some old guides for this type of design, but I did not find any that illustrated the forces in the section. I decided to create two models. A unit width section parallel to the load, and a second model of the total footing length. The unit width was subjected to the gravity loads using different soil subgrade modulii. Using a number of section cuts I was able to plot the forces and determine the bearing pressure.. The second model was subjected to an imposed vertical deflection to simulate heaving if that were to occur. I thought I would share if anyone is interested.

Load Summary:


Deflected Shape:


Moments Due to 2" Vertical Movement:

 

[XR250]

I design these by figuring out how many feet of "backspan" slab is req'd to balance out the eccentricity and then reinforce it accordingly.

 

[Brad805]

Thanks XR. I am curious what thickening you might have for something like the example? The bldg is 40'x80'. We rarely do these. Way too much risk for CH soils and frost. The pay is crap too. There is another handing out a simple un-thickened design like tick tacks, so I thought I would take a closer look.

 

[SE2607]

I design these by figuring out how many feet of "backspan" slab is req'd to balance out the eccentricity and then reinforce it accordingly.

This might be a bit of a hijack, but do you consider the weight of the slab as part of the load?