Where: ( M ) = internal bending moment, ( y ) = distance from neutral axis, ( I ) = moment of inertia of cross-section. The differential equation:

[ \sigma_x = -\fracM yI ]

[ \fracKLr, \quad r = \sqrt\fracIA ] For a pin-jointed truss in equilibrium at each joint:

Where: ( V ) = shear force, ( Q ) = first moment of area about neutral axis, ( I ) = moment of inertia, ( b ) = width at the point of interest.