Greetings,1) I'm trying the problem 5.16 US Mat Combined Foundation 1 from the verification manual (Pg. 364)
The results I get don't match with those mentioned in the results summary table. The longitudinal moment on bottom in particular is drastically different. I am using the slab designer -> Design -> Result summary to generate these values.
Please let me know if I'm doing something wrong.
USMCF1.sfa
2) Another question I have is regarding to the problem 5.14 US Pilecap foundation 2 (Pg.345) and 5.12 US Combined foundation 2 (Pg. 328)
The results match with those specified in the verification manual only when I manually change the Dead weight factor to 1 in the apply self weight and dead weight factors in the loads & factors drop-down. Is this correct? Shouldn't we be using the ACI factors (Auto generate provides this)?Thank you
Regarding your second question:
The hand calculation in the verification manual was performed based on the a load factor of 1.0 for self weight, and, a load factor of 1.4 for the imposed loads from the column. You can find this mentioned immediately after the heading "Factored Design" in example 5.14. We agree that, in order to be exact, the hand calc should use a selfweight factor of 1.4. But the primary objective of these examples is to demonstrate the procedure used in the program, and hence, some differences from the academically correct method, like this, are present.
We will rectify this example so that the selfweight of the pilecap too has a factor of 1.4.
For the combined footing, if there is no uplift for the ultimate load cases, it shouldn't matter what factor is used for selfweight because it will be counterbalanced by an equal and opposite soil pressure. However, some marginal differences may occur because of the approximations used in calculating the shear forces and bending moments from a pressure distribution that varies along 2 directions.
We will get back to you with our observations regarding example 5.16.
Answer Verified By: Vic Ayyappan
Thank you Kris!