Gordon's formula

A column formula. Also called Rankine's formula:

<math> P = \frac{s}{1+a\frac{l^2}{r^2}} </tex>

where:

<math>P</tex> = the allowable unit stress for the column

<math>s</tex> = the allowable unit stress for blocks

<math>a</tex> = a constant depending on end conditions, etc.

<math>l</tex> = the unsupported length of the column

<math>r</tex> = the least radius of gyration in reference to an axis normal to the plane in which flexure takes place