How do you calculate combined footings?

Design Combined Footing

1. Footing has two columns.
2. 300mm square column has 100kN and 500kN live and dead loads respectively.
3. 400mm square column has 200kN and 800kN live and dead loads respectively.
4. Spacing of columns 3m.
5. fck = 30N/mm2.
6. fyk = 500N/mm2.
7. Assumed footing thickness 500mm.
8. Allowable bearing pressure 200N/mm2.

What are the two criteria for design of rectangular combined footing?

The combined footing may be rectangular, trapezoidal or Tee-shaped in plan. The geometric proportions and shape are so fixed that the centeroid of the footing area coincides with the resultant of the column loads. This results in uniform pressure below the entire area of footing.

Which footing supports two or more columns?

combined footing
A spread footing which supports two or more columns is termed as combined footing. The combined footing may be of the following kinds: Combined footings are invariably constructed of reinforced concrete.

What is the preferable way of providing combined footing?

This type of footing is preferred when only single column is appearing in the foundation plan of a particular project. Combined footing: Combined footing supports two or more column loads. These may be continuous with rectangular or trapezoidal in plan.

What are the design principles of combined foundations?

A combined footing runs between two or more columns and obviates the need to have multiple isolated footings placed at each column location. Combined footings help to resolve applied stresses throughout the footing and hence have greater stability and can carry significantly more stresses into the ground.

What are the conditions under which combined footings are used also explain the design of combined footing?

A combined footing is used in the following conditions: When two columns are very close enough to each other such that their footing overlap. When the load-bearing capacity of the soil is low, the requirement of more area under the individual footing.

When combined footing is required?

Combined footings are provided when distance between two columns is small and soil bearing capacity of soil is lower and their footings overlap with each other.

Which are the design principles of combined foundation?

Under what circumstances combined footing are provided?

What are the two types of combined footing?

There are three different types of types of combined footings :

• Slab Type Combined Footing. Slab type combined footing supports two or more column with bottom slab only.
• Slab-Beam Type Combined Footing.
• Strap-Beam Type Combined Footing.