The one-way shear check in footing is a structural check performed during the design of concrete footings to ensure they can safely resist shear forces that could cause failure resembling that of a wide beam.
In structural engineering, a footing transfers loads from a column or wall to the underlying soil. It must be strong enough to prevent various failure modes, one of which is shear failure.
What the Check Recognizes
As highlighted by the reference, a one-way shear check:
"...recognizes that the footing may fail in shear as a wide beam along a critical section at a distance d from the column face in each direction."
This means engineers consider the footing as a wide concrete beam supporting the column load. The critical area for this type of failure occurs at a specific distance away from where the load is applied.
The Critical Section
The critical section for the one-way shear check is located at a distance 'd' from the face of the column (or wall) in each direction. Here, 'd' represents the effective depth of the footing (the distance from the top concrete fibers to the centroid of the main reinforcement).
Imagine the footing bending under the column load; the maximum shear stress for this "wide beam" action occurs at this distance 'd'.
Why it's Called One-Way Shear or Beam Shear
The failure mode resembles the shear failure seen in concrete beams. Because the critical section extends across the full width of the footing in a particular direction (like a beam), it's referred to as "one-way shear" or "beam shear."
| Aspect | Description |
|---|---|
| Failure Mode | Shear failure acting like a wide beam. |
| Critical Section | Located at a distance 'd' from the face of the column/wall. |
| Direction | Checked independently in each main direction of the footing. |
| Alternative Name | Beam Shear |
The Purpose of the Check
The primary purpose is to calculate the shear stress at the critical section and compare it against the concrete's allowable shear strength.
- Calculating Shear Force: The shear force acting on the critical section is typically calculated based on the load transferred from the soil outside this critical section.
- Comparing Strength: This calculated shear stress (or force) must be less than the factored shear strength provided by the concrete, often enhanced by shear reinforcement if necessary.
Ensuring the footing has sufficient depth and/or reinforcement to pass the one-way shear check is crucial for preventing structural failure under anticipated loads. It's one of several shear checks performed, alongside the two-way (punching) shear check, which considers failure around the column perimeter.
