Hello,
Please help me determine why my model is failing.
I am designing a combined shallow footing for a four column tower in Staad Foundation Advanced V8.3.0.20 but I'm having some difficulty. The tower has four columns with identical base plate elevations. Each column will have a 3.67' high pedestal that extends 0.67' above grade elevation. I used Staad.Pro to create the structural model and imported the load cases into SFA. Since my staad load combinations were imported as individual load cases, I ended up deleting them and using SFA's "Generate Load Combination" feature and then slightly modified the combos. The mat self weight was applied to the Dead Load case only and all of the job relevant inputs where added. Since the loading is nothing exorbitant - the max LRFD compressive force is appx. 48 kips and the max uplift is 28 kips - I expected this footing to be around 14' wide x 14' long x 2' thick with No. 6 bars @ inches (both directions, top/bot).
The results of the analysis show the mat contact area near 30%, the bearing pressure reaches over 4 ksf in service loading, and all reinforcing locations are failing.
Thank you in advance for your assistance and please let me know if I can provide any further details.
P.S. - I have attached my .SFA model.
Regards,
Matt W.communities.bentley.com/.../Truck-Loadout-Bridge-FDNs.sfa
