I have had to design a few large base anchorage/ base plates in the past for both moment and uplift.
To be perfectly honest, I designed them one a piece-by piece basis using basic stress analysis, ASD and applying allowables where I could. I have always found Blodgett to be VERY practical and I used many of the same approaches.
Most of the large bases you see basically try to get away from having a plate in bending by substituting what is basically a built up beam to take the bending while transmitting tensile forces to the anchorage.