I'm working in Staad Foundation Advanced connect Edition version 08.00.00.00 and am having some confusion about reinforcement and how it's calculated.
1) In the design parameters, the value for bottom cover appears to be from the top of the pile. However, in at least one instance in the GA drawing, this distance was shown from the bottom of foundation. We found it difficult to determine which d was actually used for the calculation of the required reinforcement. Is there a place where we can confirm which d value is used?
2) In the verification manual, you have the calculation used for the reinforcement ratio as follows:
So Resisting Moment = Mnz= Muz/ϕ = 744.44 ft·kip
Rn = Mnz/b·d2 = 0.147 Ksi
2·m·Rn/fy = 0.0864 <1 , Hence OK
ρ = 1/m· (1-√1-2m·Rn/fy) = 0.0025
In your calculation sheet, you have the governing moment Mtl (which I assume to be the same as the verification Mnz), and then the reinforcement criteria "calculated Reinforcement Ratio (R)" and Rmax. Then compare R to Rmax and 0.0018 and say that "R is accepted". I created a spreadsheet to perform this calculation and have been unable to get the rho to equal "R". Should the value listed as R be equal to rho in the verification manual?
3) If so, the calculated reinforcement ratio was 0.0025 for a 7' wide by 27" deep foundation with a moment of 148.6 k-ft (fy 60, f'c 4ksi). In my calculation, this value should have been closer to 0.0009 to 0.0011 in which case Asmin (0.0018) would have controlled. And the program accepted #7@12 which is just above the Asmin. Why is the reinforcement provided below what is required by the "calculated reinforcement Ratio"?
Thanks in advance.
Ryan
Ryan : First of all I would like to request you to uninstall the version 08.00.00.00 and install the version 08.02.00.31 as we addressed lot of issues in that version. The clear cover is measured from the top of the pile and not from the bottom of the pile cap. The Mt1 should be identical to the Mnz as you mentioned. The R should also be equal to Rho in the verification manual. Please check the results with the new version and if you still observe any discrepancy we will be happy to look into it. Once you get the software installed, pick a verification example from the verification manual and run the corresponding model in SFA and it will be a lot easier for you to check the numbers. The verification models are available within the installation folder C:\Users\Public\Documents\STAAD Foundation Advanced\Examples
Sye,
Please see the attached. I have the same issue with the newer version.
I think I only have a disagreement with the Calculated Reinforcement Ratio R. It appears that it is higher than anticipated.
I was originally was basing the reinforcement off of the rho*A gross instead of using the b*d. Just out of curiosity, does the program calculate the minimum reinforcement off of the full section? ACI section 7.12.2.1 (which I believe is where you are calculating the Asmin from), has it as the gross area, but your calculations make it appear like it is only comparing rhomin, rho max, and rho calculated and then calculating the Asmin from rho*b*d.
Ryan: You mentioned about an attachment but I do not see any. The Asmin is calculated based on the gross section ( width x overall depth )whereas the required reinforcement is calculated based on the effective depth x width
Sorry, for some reason I could upload the entire PDF. If you need the rest of the sheets I can send them to you.