Leaderboard

Well Zaib it depends! If you have assumed pin base then it means moment at base = 0 and you have only the vertical load reaction. If this is the case then the footing area required Areq = P/180 where P is kN and Areq is in m². Then you can convert this area into a square footing or a rectangular footing as you need. Or if you have moments things get more complicated so you can either do it manually or choose any software; like SAFE, PROKON or MIDAS. I am not aware of PROKON, so I would tell you what to do in SAFE. Start a new model and make isolated foundations (preliminary sizing) and put a node in the center of footing and put the vertical reaction on this node. Run the analysis check the bearing pressure and see if the sizing is ok. If not then change footing sizes and re-run. After it design it on SAFE for reinforcements.

I found another version, scanned slightly better, its attached below. Rectangular Concrete Tanks - PCA - US.pdf