I am examining a high rise building project of 30 floors with a podium underneath and 2 basements. The structure in the tower and the podium varies between flat slabs, steel structure for wide spans, a huge shear wall around the tower's core, etc. The basement space has become inefficient as a parking area so I'd like to transfer this whole structure to an 8x8 or 16x16 grid of columns by using the transfer floor/slab. How can I estimate the required thickness of the transfer floor?