Form of the relationship between corrugated fiberboard caliper t_c and effective shear thickness t_g for determining an in-plane shear stiffness equivalent to a thin plate. The unit in-plane shear stiffness G_u of a thick composite plate is multiplied by

to get an effective thin plate stiffness that incorporates the thick plate transverse shear stiffness. Subscript w corresponds to the thickness ratio found for a single wall, double wall, or triple wall board. Subscript 0 corresponds to the limit as thickness approaches zero. Effective shear thickness equals