Expert: Arshad Khan - 9/6/2006

Question
Dear Mr Khan,

I have this situation:

a. 3 story building with raft foundation of 60cm depth.
b. forklift movement on ground floor (FL3 class according to EN), with solid tyres. 2 fortclifts will move at the same time.
Its characteristics are :  
Number of wheels = 2x2
track with, front= 1,054m
track with, rear= 1m
overall length=3,27m
overall width = 1,2m
unladen weight = 4577Kg
Axle loading with load = 6273Kg
Axle loading without load = 2268Kg

c. The architect wants to have 15cm screed  above the raft foundation,(dont ask me why, he says he is not usually pleased with the quality of the surface accomplished by the concrete of the foundation!) so I am reinforcing it also cause it will crack otherwise.
d. The healthy soil where I can seat my foundation, is 1m below the ground surface and the architect wants the finished floor level to be +20cm above the physical ground surface.So, there is a space of 45cm between the below surface of the foundation and the healthy soil.


My questions are:

1. Is reinforcement Y8-200#(up+down) of the 15cm slab, adequate or it needs more?
2. The 60cm foundation turned out of the design, meaning it can bear the loads of the building.I haven't considered the 15cm slab above it, nor the movement of forklifts, because my software can't do it! Must I increase the depth or reinforcement of the raft foundation, so that it can bear the 15cm slab above it and the movement of forklifts? And how much approximately?
3. What is the best way to fill the 45cm (look at d), with concrete C15, or with layers of compacted soil?

Thank you in advance,

Emily Spanou  

Answer
Hi Emily,

I do not design structures over this forum, but I will answer your questions as far as the info you have given.

1. Y8-200 T and B EW should be fine.

2. Best to fill the gap under the raft with C10 or C15 concrete, or else compacted hardcore.

I hope that helps!

Kind regards,

Arshad