Raft foundations 1
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Raft foundations are used to spread structural loads over a large area and are classified as plain slab, beam and slab, or cellular rafts. They consist of a concrete slab extending over the entire loaded area, sometimes stiffened with ribs or beams. Raft foundations reduce differential settlements and are suitable for soft soils as they spread loads over a larger area. Reinforcement runs in both directions in the slab and downstand beams can add rigidity.
![TYPES OF RAFT FOUNDATIONS
On the basis of structural systems, they can be
classified as
1] Plain Slab Rafts
2] Beam & Slab Raft
3] Cellular Raft](https://image.slidesharecdn.com/raftfoundations-1-170824053215/85/Raft-foundations-1-2-320.jpg)
![Based on the methods of their support, Raft can be
1] Raft supported on soil
2] Raft supported on pile
3] Buoyancy Raft](https://image.slidesharecdn.com/raftfoundations-1-170824053215/85/Raft-foundations-1-10-320.jpg)
Raft foundations 1
- 2. TYPES OF RAFT FOUNDATIONS On the basis of structural systems, they can be classified as 1] Plain Slab Rafts 2] Beam & Slab Raft 3] Cellular Raft
- 5. Buoyancy Rafts are necessarily to be provided with the basements so that the weight of the soil removed Balances to large extent the imposed load.
- 6. Raft foundations are used to spread the load from a structure over a large area, normally the entire area of the structure. They are used when column loads or other structural loads are close together and individual pad foundations would interact. A raft foundation normally consists of a concrete slab which extends over the entire loaded area. It may be stiffened by ribs or beams incorporated into the foundation. Raft foundations have the advantage of reducing differential settlements as the concrete slab resists differential movements between loading positions. They are often needed on soft or loose soils with low bearing capacity as they can spread the loads over a larger area. RAFT FOUNDATIONS
- 7. Solid slab raft foundation Reinforcement runs in both directions Reinforced concrete raft 40-50 concrete blinding seals surface and provides level platform to fabricate the reinforcement matt and cages Well compacted hardcore Solid slab raft foundation
- 8. Reinforced concrete raft 40-50 concrete blinding seals surface and provides level platform to fabricate the reinforcement matt and cages Downstand beams or edge thickenings can be used to add rigidity and stability to the raft foundation. Where brick or block walls sit on the raft the extra load can be accommodated by a beam within the raft. Reinforcement cages are constructed to act as beams within the raft foundation Solid slab raft foundation with Down stand beam
- 9. Edge beam and reinforcement extended to carry brickwork cladding. Toe cast in to slab to carry brickwork cladding. Hides the concrete raft below the ground Raft foundation with extended toe to carry brickwork
- 10. Based on the methods of their support, Raft can be 1] Raft supported on soil 2] Raft supported on pile 3] Buoyancy Raft
- 11. Reinforcement - raft foundation
- 12. Reinforcement - raft foundation