Study 4_foundation.sfaPDFHi,
Please see attached STAAD foundation file and report. Under GLOBAL SETTINGS/RIGID FOUNDATION SETTINGS, I have the "Check Minimum Reinforcement on Top and Bottom Combined" box checked but the program doesn't seem to be doing it. The attached report shows As = 2.07 in2 (0.0018*48*24) and rebar are still 5-#6 (As provided = 5*0.44=2.20 in2) Top & Bottom. Can you please let me know if I'm missing something?
Thanks,
Dennis
For the combined footing job you have defined, the bottom reinforcement is being calculated based on the cantilever deflection of the projection and the moment is calculated at the face of the column ( tension at bottom ). The top reinforcement is being calculated based on the moment at midspan (tension at the top). So the reported top and bottom reinforcements are for different locations along the length of the footing. You do not have to provide both top and bottom reinforcement at the same location and you may curtail bars after satisfying the development length and any other detailing requirements. As of now, the software does not have the ability to tell you that.
Yes, I know the theory for combined footing design but my question refers to the "minimum reinforcement" and the option in the program "Check Minimum Reinforcement on Top and Bottom Combined" doesn't seem to be working. Again the program calculated Asmin = 2.07 in2 but even though I have the option "Check Minimum Reinforcement on Top and Bottom Combined" checked, the program is providing 5-#6 (2.20 in2) Top and 5-#6 (2.20 in2) Bottom reinforcement. In other words the program is not splitting Asmin=2.07 in2 between the top and bottom section of the footing.
Follow-up on this. Please advise.
I agree that the minimum reinforcement requirement needs to be satisfied based on reinforcement provided at top and bottom combined. So you do NOT need to provide 5-#6 bars at both top and bottom. The way the software is reporting the reinforcement needs to be modified. I have notified the product management team about it.