While designing a structural part of a 4-storied residential building, it is found that the clear distance between two isolated footing edge is very less and above all total area of isolated footing is around 80% of floor area of the building . As Assam is a earthquake prone zone, can anyone give me some advice. I prefer raft/mat foundation - if so how much it will cost effective and is there is any other sugesstion, soil patameter, clay expansive soil and bearing capacity is 9.5T/sqm maximum load on column is around 90T.
Foundation for 4-story structure, earthquake zone
Dear Manideep Sen I am not a structural engineer, but from my experience I think raft/mat foundation is the best solution in such cases. Regarding that Assam is an earthquake zone, then you should use shear walls.
I am sending you two photos which show the mat foundation used in one of the buildings inside the campus of the Islamic University of Gaza, over here the whole floor area acts as one footing for the total number of columns. As you can notice the shear walls used to separate each part of the building so that it will behave as a single part at the time of earthquake.
I sent the photos to your e-mail so it will be clear to you. Wishing you all the best, and try to take some pictures of your work, it will help you so much in the future. Salem Arafat.