MAT FOUNDATION (Overturning)

RE: MAT FOUNDATION (Overturning)

desideratus — Thu, 22 Jun 2017 12:31:42 GMT

Many thanks Sye, this really helped me. This is a very important issue mainly in the case of the
structure I am dealing with where those moments are substantially increased due to slab thickness.
Best regards,

RE: MAT FOUNDATION (Overturning)

Sye — Thu, 22 Jun 2017 00:55:38 GMT

I checked with the STAAD Foundation Select Series 4 (05.03.00.34) and confirm that the horizontal shears were considered to be at the base of the mat and so no overturning moments were calculated. When one includes the pedestal, the moment is calculated by multiplying the shear x depth of pedestal. Mat thickness is not considered for calculating the moment.

The behavior is certainly different for later versions of the product ( STAAD Foundation Advanced ) in which the shears are multiplied by the thickness of the mat. So in SFA, when no pedestal height is input, the moment arm = thickness of the mat. When pedestal height is provided moment arm = pedestal height + thickness of the mat.

I hope this helps.

RE: MAT FOUNDATION (Overturning)

desideratus — Wed, 21 Jun 2017 15:11:11 GMT

Dear Sye,

I was working with Staad Foundation Series 4.

Now, I made a try with Staad Foundation Advanced 7.2, I specified a plate 0.50 m thickness,
once it run, I got the FoundationAnalysis. std file which is generated in the StaadFoundation ANALYSIS directory.
I compared the StaadPro original reactions against the Loads applied in that file,
and I found that StaadFoundation Advanced 7.2 do consider the slab thickness (along with pedestal height) for calculating
the resulting moments applied at the foundation base due to the horizontal forces applied at the pedestal top.

I had no time to make a similar checking for Staad Foundation Series 4
So, as a consequence I have so many doubts now about my Staad Foundation Series 4 results.

Would you please clarify this.
Is it just a matter of versions?
Does Series 4 certainly does not consider the slab thickness?

Many thanks in advance for your so kind help
Best regards,

RE: MAT FOUNDATION (Overturning)

Sye — Tue, 20 Jun 2017 02:41:04 GMT

For your mat foundation, you may account for the additional moment by specifying pedestal height of 1 m. Detailed explanation on the topic is available at

communities.bentley.com/.../33069.does-sfa-account-for-the-moments-due-to-horizontal-shears-in-foundation-design

RE: MAT FOUNDATION (Overturning)

desideratus — Tue, 20 Jun 2017 02:01:49 GMT

Note: My slab has 1 meter thickness, so I need to be sure that the software calculate the produced moment due to slab height