Important Question And Answer: Civil - Footings And Rafts

FOOTINGS AND RAFTS

1. Under what circumstances, a strap footing is adopted?

When the distance between the two columns is so great, so that trapezoidal footing is very narrow and so it is uneconomical. It transfers the heavy load of one column to other column.

2. What is a mat foundation?

It is a combined footing that covers the entire area beneath a structure and supports all the walls and columns.

3. Where mat foundation is used?

It is used when the area of isolated footing is more than fifty percentage of whole area or the soil bearing capacity is very poor.

4. Define spread footing?

It is a type of shallow foundation used to transmit the load of isolated column, or that of wall to sub soil. The base of footing is enlarged and spread to provide individual support for load.

5. What are types of foundation?

shallow foundation , deep foundation

6. What are the footings comes under shallow foundation?

spread footing or pad footings , strap footings, combined footings, raft or mat foundation

7. What are the footings comes under deep foundation?

pile, caisons(well foundation)

8. Define floating foundation?

It is defined as a foundation in which the weight of the building is approximately equal to the full weight of the soil including water excavated from the site of the building.

9. What is mean by proportioning of footing?

Footings are proportional such that the applied load including the self weight of the footing including soil .the action are not exceeding the safe bearing capacity of the soil.

10. What are the assumptions made in combined footing?

- the footing is rigid and rests on a homogenous soil to give rise to linear stress distribution on the bottom of the footing.

- the resultant of the soil pressure coincides with the resultant of the loads, then it is assumed to be uniformly distributed.