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Shear Stress

Key Concepts: Consider rubbing your hands together. The forces exerted between your

hands during this action are an example of shear force. The shear force per unit area is the

shear stress.

In a Nut Shell: Transverse loads, P, on a plate, ABC, result in shear forces and therefore

shear stresses in the plate as depicted in the top and middle figures below. Shear stresses

also occur in beams.

Beams are important structural elements. Examples include I-beams, wide˗flange beams,

and box˗section beams. In general beams are of a length considerably longer than the

dimensions of the X-section. When a load, P, acts on the beam (bottom figure) with

pin support on left end and a roller support on the right end) it deforms (dotted line) the

beam causing a bending moment. The result is that the change in bending moment along

the beam develops shear forces and shear stresses in the beam (along the x-axis).

Common units for normal and shear stress are psi, ksi, MPa, N/mm² (English/Metric)

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