1. The problem statement, all variables and given/known data I'm reading a paper and I'm trying to understand how does the author arrived from equation (1) to the following buckling load equation (2). I know that the author substitutes equation (1) with the dimensions of the geometry but I still could not understand how he comes to last term 6e/t in equation (2). 2. Relevant equations P=Aσmax / [1+ec/r2] (1) P=Btσy / [1+6e/t] (2) where; A=cross-sectional area of column e=eccentricity B,t=geometry of specimen (refer to attached figure) c= distance from neutral axis to the outer fiber where σmax occurs r, radius of gyration, r2=I/A where I is the moment of inertia computed about the bending axis 3. The attempt at a solution I tried to play around by substituting r2 with I/A. But I don't know how can I expand the results afterwards. Maybe there are some simplifications that I missed.