1

Combined Footings

A. Rectangular combined footingB. Trapezoidal combined footingC.Strap footing

Combined Footings

Rectangular combined footing

2

Combined FootingsA. Determine the area of the foundation

B. Determine the location of the resultant of the column loads

C. For a uniform distribution of soil pressure under the foundation, the resultant of the column loads should pass through the centroid of the foundation.

D. Once the length L is determined, the value of L1 can be obtained as follows:

E. The width of the foundation is then

3

Cantilever Footing

Shallow Foundation TypesStrip Footing (wall loads)

4

Mat Foundations

5

Why Mat foundation?

• Soil properties are insufficient so that building loads can not be carried by single or combined/continuous foundations

• Because of high building loads: separate footing dimensions are so large that they overlap

• Risk of differential settlement

• Variable and uncertain building loads

• Variable lateral loads

• High buoyancy forces due to high ground water Table

• Requirement for waterproofing

• Foundation: structure that transmits loads to underlying soils.

Shallow Foundations

Df = Embedment DepthB = Characteristic Length (Coduto)

Deep Foundations(Df/B > 4.0)