Mat Footing Section

The mat foundation which is sometimes known as a raft foundation is a combined footing that could cover the whole area under a structure supporting several walls and columns.

Mat footing section.

It is a suitable solution for low bearing capacity soil spread footing cover about 70 of the structure high structure loads soft pockets or cavities of in the soil to unknown extent raft and highly compressible soil that extends to a great depth. Bars that are placed in the interior layers should follow. Two layers one mat or four layers two mats at both the top and bottom. It is common to use mat foundation or deep basements to transfer the column loads to the underlying soil as well as provide floor slab for the basement.

Per code section 7 12 2 2 the bar spacing is limited to five times the slab thickness or 18 in. Basic design criteria concentrically loaded d 2 all sides c critical section for two way shear b critical section for one way shear a critical section for flexure outside face of concrete column or line midway between face of steel column and edge of steel base plate typical extent of footing typical d foundation design 8. Flat plate raft is used in the small and lightweight load structure. There are following types of mat foundation flat plate raft.

Plate thickened under columns. Mat foundations are sometimes preferred for soils that have low load bearing capacities but that will have to support high column or wall loads. The result is footing areas that can be large in relation to the cross section of the also chapter 4 october 2015 chapter 4 footing foundations 4 1 introduction footing foundations also known as spread combined or mat footings transmit design loads into the underlying soil mass through direct contact with the soil immediately. Two way slab and beam.

Under some conditions spread footings would have to cover more than. A mat foundation is used when the subsoil is weak and column loads are so heavy that the conventional spread footings cover more than 50 of the building area. Mat foundations are sometimes preferred for soils that have low load bearing capacities but that is going to need to support high wall or column loads. When a spread footing columns can cover up to 50 of the foundation area.

A mat foundation spreads out under the footprint of the building and declines the contact pressure compared to conventional strip or trench footing. It is a combined footing that may cover the entire area under a structure supporting several columns and walls. Code section 15 10 4 also sets the maximum spacing of mat reinforcement at 18 in.