# Wood method

The Wood method, also known as the Merchant–Rankine–Wood method, is a structural analysis method which was developed to determine estimates for the effective buckling length of a compressed member included in a building frames, both in sway and a non-sway buckling modes.[1][2] It is named after R. H. Wood.

According to this method, the ratio between the critical buckling length and the real length of a column is determined based on two redistribution coefficients, ${\displaystyle \eta _{1}}$ and ${\displaystyle \eta _{2}}$, which are mapped to a ratio between the effective buckling length of a compressed member and its real length.

The redistribution coefficients are obtained through the following expressions:

${\displaystyle \eta _{i}={\frac {K_{c}+K_{i}}{K_{c}+K_{i}+K_{i}1+K_{i}2}},\quad i=1,2}$

where ${\displaystyle K_{i}}$ are the stiffness coefficients for the adjacent length of columns.

Although this method was included in ENV 1993-1-1:1992, it is absent from EN 1993-1-1.