Which of the following statements about strap footings is INCORRECT?
Which of the following statements about strap footings is INCORRECT? Correct Answer The soil pressure is uniform beneath few individual footings.
Concepts:
A strap footing is a type of combined footing, consisting of two or more column footings connected by a concrete beam. In other words, when the independent footings of two columns are connected by a beam, it is called a strap footing.
This type of beam is called a strap beam. It is used to distribute the weight of either heavily or eccentrically loaded column footings to adjacent footings.
The strap beam doesn’t remain in contact with soil, and thus doesn’t transfer any pressure to the soil. The strap, assumed to be infinitely stiff, serves to transfer the column loads on the soil with equal and uniform soil pressure under both footings.
A typical sketch of strap footing is shown below:
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Applications:
1. A strap footing is often used in conjunction with columns that are located along a building’s property. Typically, columns are centered on column footings, but in conditions where columns are located directly adjacent to the property line, the column footings may be offset so that they do not encroach onto the adjacent property. This results in an eccentric load on a portion of the footing, causing it to tilt to one side. The strap beam restrains the tendency of the footing to overturn by connecting it to nearby footings. (Refer above Figure ‘a’)
2. It is also used when the distance between the columns is so great that a combined trapezoidal footing have high bending moments. In this case the column is provided with its independent footings and a beam is used to connect the two footings. (Refer above Figure 'c').
