\[q=\frac{VQ}{I}\]
Variables
qshear flow (N/m)
Vinternal shear force (N)
Qfirst moment of area about the neutral axis (m³)
Isecond moment of area about the neutral axis (m⁴)
Description
What is this formula?
Shear flow is the distributed horizontal shear force transmitted through a structural cross-section. It is widely used in built-up members, welded connections, riveted structures, and thin-walled sections.
When to use it
Use this formula when determining how shear forces are transferred between different parts of a structural member. It is especially important in composite beams, plate girders, aircraft structures, and welded steel sections.
Example
A plate girder has:
V = 150000 N
Q = 0.004 m³
I = 0.020 m⁴
Formula:
q = VQ / I
Substitution:
q = (150000 × 0.004) / 0.020
Result:
q = 30000 N/m
Applications
Built-up beams, welded connections, riveted joints, plate girders, thin-walled structures, bridge engineering, and aerospace structural design.