Hi,
First of all kudos to the administrators for taking the initiative of providing this platform. I am new here and i hope to contribute and gain maximum from this portal.
I am designing a B+G+2 RCC Building with a foot print of 30x40(ft). Owing to the architectural requirements columns have been provided along the edges only giving a span of 30ft c/c in x dir while 14ft in y direction. The Allowable bearing capacity is 0.8 tsf for raft. There is a basement retaining wall 8ft high while the story height is 12ft. So, the RCC wall is only for soil retention. Initially, i tried to provide isolated footings but the bearing pressure was well above the allowable. So, i resorted to raft foundation. I didn't model the RCC wall in SAFE to check the punching shear; which eventually lead to a raft thickness requirement of 27 inches. My questions are:
1) Is there a way to optimize the raft by NOT providing the 27" thickness all over the area? Like, the area in vicinity of columns can have 27" thick while the remaining raft can have lesser thickness? If there is a way, please provide some details of doing it in SAFE. Considering the size of this project, it may not save much but i need to learn this technique of modeling the raft with variable thickness.
2) There is always a failure of bearing pressure when columns are located along the edges of raft. Yet it's quite a common practice to provide columns along the edges of raft. How such rafts are designed? I am facing the same problem here.
Thanks
