Raft Foundation, Problem With Isolated Line of Columns

[YuleMsee]

I'm designing a gate house on a fill site, the fill is about 4m deep, 4 yrs old. the area has been used as the entrance to the construction site for those 4yrs with a lot of truck traffic.
There is a guard house at the centre then two lanes on each side (entrance / exit) then two lines of roof slab support columns on gridline G1 & G7.

Doing a raft for those isolated columns is turning into a headache. Any ideas?

 

[YuleMsee]

 

[KootK]

Doing a raft for those isolated columns is turning into a headache. Any ideas?

In what sense is it a headache to you?

I might do grade beams at the ends and not tie the ends into the central raft if you can demonstrate that the roof slab could handle a little differential movement. I don't know how effective the raft would be in ironing out differential settlement at the ends anyhow unless you're willing to make it very thick.

 

[r13]

Are the east and west structures placed on/near the property lines? For the corner columns, albeit a little difficult, I see combined footing could be the solution.

 

[YuleMsee]

@kootk, as you have stated mostly worried about differential movement. Just a rectangular section, inverted "T"?

@retired13, no, there is no contraints of any sort

 

[r13]

Then do a normal spread footing design, if the bearing/bending of the edge column are too much to handle.

 

[Agent666]

If its a temporary structure as you suggest. Design the roof over to accommodate the differential settlement might be an option?

In steel for example the use of connections that could accommodate the rotations could deal with it?