Basics in Building Construction

Basics in Building Construction 4(2+2)

Lesson 02 : Shallow Foundations

Strap Footings

• If the independent footings of two columns are connected by a beam, it is called a strap footing.
• It may be used where the distance between the columns is so great that a combined trapezoidal footing becomes quite narrow, with high bending moments.
• In such case, each column is provided with its independent footings and a beam is used to connect the two footings.
• The strap beam does not remain in contact with soil and thus does not transfer any pressure to the soil.
• The strap, assumed to be infinitely stiff, serves to transfer the column loads on to the soil with equal and uniform soil pressure under both footings.
• The figure 12 below shows the strap footing for two columns A and B. Column A is so near to an existing wall that the footing of the wall does not permit the independent footing of column A to spread out towards the wall, though it has freedom in other directions .