By: Javier Encinas, PE | May 8, 2016
ASDIP FOUNDATION includes the design of concrete strap footings. This structural engineering software is based on the latest ACI 318 provisions. This post covers the steps in the design of strap footings when subjected to a combination of vertical loads, horizontal loads, and bending moments.
A strap footing usually supports two columns, so it’s a special type of combined footing. If a property line exists at or near the edge of an exterior column, a normal isolated footing would be placed eccentrically under this column and it would tend to tilt. This problem may be prevented by connecting this footing with the adjacent interior footing by a strap concrete beam. The use of a strap footing may be justifiable where the distance between columns is large and a normal combined footing is impractical due to the required large excavation. For construction simplicity, it is common practice that the bottom surfaces of the exterior footing, the strap beam, and the interior footing be at the same elevation, but the thickness of each element may be different, depending on the strength requirements.