Dear Community,
I was reading this article on how to check the stability of Mat foundations in STAAD.Pro.
https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/29973/stability-checks-for-a-mat-foundation-modeled-in-staad-pro
With this I have a question:
In checking Sliding ratio, I get it that I can get the results by dividing the product of vertical loads and friction factor to the corresponding horizontal loads on every load case.
But in checking Overturning moment ratio, I do not know how to get the results on every load combinations that I have since vertical and horizontal loads are combined. Is there any way I can get the overturning ratio without using STAAD foundation ?
In addition, if the structure has a bracing system it produces horizontal loads on top of pedestals even if it is in Gravity loads.
Yes I agree that although checking the sliding should be pretty straight forward, checking overturning for combinations would require some work. Basically you would have to find out the restoring/stabilizing moments by analyzing the gravity cases ( appropriately factored by serviceability load factors). Even if there are braces, you should be fine as the restoring moment reported would include the contribution of the moments generated from the horizontal reactions as well. For symmetric brace arrangements the horizontal reactions will balance out for gravity only cases.
Subsequently you can find out the disturbing moments due to factored lateral forces acting alone. You can then find the factor of safety due to overturning.
Having said that I would suggest that you use STAAD Foundation Advanced for foundation design as all of these checks are automatically carried out by the software and it would save you lot of time and effort.
Thanks ! I just need to work on an excel spreadsheet so I can generate tabulated results regarding stability ratios.
Dear Sye,
As i know that STAAD Foundation advanced will not perform any sliding and overturning check for the MAT foundation.
Is it included in latest edition ? let me know.
Thanks,
Virat Dave.
Yes. Sliding and Overturning checks for Mat foundation are available since build 8.3.0.20 of SFA. I just tested the feature in the latest version of the program - Version 9.0.0.9 - and I am happy to report that it is working quite well.