Q · q · τ

Thin-Wall Shear Flow

Move the cut position along the wall to see how the first moment Q builds up from a free edge, then converts into shear flow q = VQ/I and average thin-wall shear stress τ = q/t.

Section type
Vertical shear V
Positive = downward, negative = upward.
Wall thickness t
Characteristic width b
Characteristic height h
Cut position along wall
First moment
Section I
Shear flow
Average shear stress

Cross-section, accumulated Q region, and shear-flow direction

thin-wall centerline accumulated area used in Q local cut position shear-flow direction

Q(s), q(s), and τ(s) along the wall path

Zhao Qin at SU and ChatGPT 2026