I am wondering what the difference is between the "Max Unfactored Soil Bearing" and the "Max Average Unfactored Soil Bearing". I have referred to the technical notes for the analysis of spread footings and I was able to replicate the "Max Unfactored Soil Bearing" value for both my gravity and lateral members in my model, and this was perfect. Yet, I am now trying to look at the soil bearing for a unique case...I have a group of 3 columns sharing one large spread footing. The way I modeled it is accurate to what is currently constructed (this is an analysis for expansion of an existing building). I have a continuous footing beneath two lateral columns, and a spread footing under the one gravity column (this column has eccentricity), and these two foundations overlap. I was able to replicate the values for the continuous footing, but surprisingly not the spread. Or I did...but rather than obtaining the "Max Unfactored Soil Bearing" like I was for all other foundations, my calculations produced the same value for the "Max Average Unfactored Soil Bearing".
Something that may be affecting this, but I am unable to determine how, is that the gravity column atop the spread footing is technically designated as "lateral", but all the connections are pinned since I want it to act as gravity. My forces do not show any moments going into my foundations, which is what I want. The reason for designating it this way is to create a load path for the braced penthouse framing on the roof of the building.
You have some moment (or some shear times thickness creating moment) such that you have a trapezoidal soil stress distribution (or triangular). The max unfactored soil bearing on the edge is reported to check against allowable pressure. The average is just that. The average can be used to tell if any part of the footing is in uplift, i.e. zero stress. Other Foundation FAQs here: https://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/8147