τ distribution across cross-section · τmax · shape factor · PASS/FAIL check
Shear stress at height y from NA:
τ(y) = V · S(y) / (I · t(y))
where S(y) = first moment of area above y, t(y) = width at y.
Design resistance:
τRd = fy / (√3 · γM0)
Most shear (≈ 90–95%) is carried by the web. Flanges carry very little. The shear diagram shows a nearly rectangular distribution in the web with small steps at flange–web junctions.
τweb,NA = V · Smax / (I · tw)