Raft Foundation Design
Raft Foundation Design
(OP)
I'm designing a raft foundation for Semi-D domestic dwellings. The contractor wants to use this form of construction, only if we can design the raft for a maximum thickness of 200mm. He does not want to use ground beams. It is only economical if we use mesh top and bottom and u-bars around the edges. The ground is good with an expected bearing capacity of 150kN/m2.I have analysed the raft structure using FEA and it will work theoretically. The maximum deflection is about 5mm at the corners. I'm worried about differential settlement and excessive cracking of the blockwork. Has anybody designed a raft foundation this thin without ground beams? Has anyone had any problems with such construction? All advice is welcome!






RE: Raft Foundation Design
Design the raft as required and ask the contractor to build it per design. Engineers should be in charge of the design not the contractor. It is your responsibility to produce safe and code compliant design.
Regards,
Lutfi
www.cdeco.com
RE: Raft Foundation Design
I agree. However, I'm only looking for some past experience from other engineers who may have designed such a crust raft. I'm not letting the contractor tell me what to do, only investigating other methods of construction!!!
RE: Raft Foundation Design
RE: Raft Foundation Design
RE: Raft Foundation Design
RE: Raft Foundation Design
Just to lend a hand here if what you are referring to is a slab raft without an beams for transfering load or stiffner.
I have designed a five storey office building as a beamless (flat) slab raft on a safebearng soil strength of 65kn/m2 but i had end walls acting as abutments for soil retension on all sides. I suppose you can analysetour structure likewise if your desin incorporates columns. But a note of warning though:
1. settlement expected over extended period of time.
2. Effect of setlement on the brckwalls.
3. The possibility of scour at the edges of slab( los of support)
4. Leakage and rising dmp problems if sab is below grade.
5. You need to seek advice from local engineers on existing same consruction.
You may require for my calclations on aileme@yahoo.com
Cheers