Transverse shear forces cause shear stress on a beam's cross-section at height y = y1:
- Shear stress is zero at the top and bottom surfaces.
- y = y-value of "cut", y = y1 (where we are finding the stress).
- V = shear force on the cross-section.
- A* = area on the opposite side of the "cut" from the neutral axis; i.e., area above y1.
- y* = distance from neutral axis to the centroid of A*, NOT the distance to the cut.
- I = moment of inertia of the entire cross-section.
- t = width of beam at y (width of cut).
- Q is the first moment of area of A* with respect to the neutral axis; Q = A*y*.
- q is the shear flow; q = t t .