Beam Shear Stress Calculator
Average and maximum shear stress in a rectangular beam section (τmax = 1.5V/A).
INPUTS
kN
mm
mm
RESULTS
Cross-section area
80,000 mm²
Average shear τ = V/A
0.75 MPa
Maximum shear τmax = 1.5·V/A
1.125 MPa
Location
τmax occurs at the neutral axis; zero at top and bottom faces
How it works
Shear stress in a beam is not uniform: it follows τ = VQ/(Ib), which for a rectangle gives a parabola peaking at 1.5× the average at the neutral axis and vanishing at the free surfaces — exactly opposite to bending stress. This is why thin webs (which carry shear) and wide flanges (which carry bending) make the I-beam so efficient.
Worked example
V = 60 kN on a 200×400 mm rectangle: A = 80,000 mm², τavg = 0.75 MPa, τmax = 1.5·0.75 = 1.125 MPa at the neutral axis — usually far below the ~0.6·fy/√3 shear strength of steel or the concrete shear capacity.
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