 Welcome back to Mechanica. Did you know that Euler's column theory gives a rough estimate of buckling load for a strut? This makes us wonder, what is Euler's column theory? Before we jump in, check out the previous part of the series to learn about what columns and struts are. First, let's look at the assumptions for the Euler's column theory. The column is perfectly straight and only axial load is applied. It is of uniform cross section throughout its length. The material is perfectly elastic, homogeneous and isotropic. The length of the column is large when compared with cross sectional dimension. The change in length due to compression is neglected and lastly, failure is due to buckling alone. Given this assumption, Euler's column formula for calculating allowable load F is given by n pi squared upon L squared, where n and I are the factor accounting for n conditions, modulus of elasticity and moment of inertia respectively. Euler's column theory, however, suffers from two basic limitations, one being the presence of crookedness in the column causing the load to not exactly be axial. Another being that this formula does not take into account the axial stresses and that the buckling load given by this formula may be much more than the actual buckling load. For struts in this category, a suitable formula is a Rankine-Gordon equation, which is a semi-empirical formula and takes into account the crushing strength of the material. It's Young's modulus and the slenderness ratio, which is the ratio of the length L of the strut to its least radius of duration K. According to the formula, the buckling load P is given as the product of elastic limit in compression and cross-sectional area A upon 1 plus the product of slenderness ratio and empirical constant A, which is dependent upon the type of ends of strut and the material of the strut. Hence, we first saw what Euler's column theory is and then went on to see what Rankine-Gordon formula is. In the next episode of Mechanical EI, find out what Laplace transforms are.