 Welcome back MechanicalEI, did you know that ancient Egyptian architecture as early as 2600 BC made use of columns to support the roofs and that monoplanes make use of struts to attach engines and other loads? This makes us wonder, what are columns and struts? Before we jump in, check out the previous part of the series to learn about what cylindrical and spherical shells are. Now columns are short thick structural members which are subjected to compressive forces, bending moments and shear forces. They are the main supports in a building or structure, they usually fail by crushing when the yield stress of the material in compression is exceeded. Struts on the other hand are long slender structural members in an assembly which are subjected only to axial compressive forces. They fail by buckling sometime before the yield stress in compression is reached. As the name suggests, the minimum load at which buckling occurs is called buckling load. At values of load below the buckling load, a strut will be in stable equilibrium where the displacement caused by any lateral disturbance will be totally recovered when the disturbance is removed. At the buckling load, the strut is set to be in a state of neutral equilibrium moving beyond which it simply buckles. Types of end conditions for a column are the major factors which influence the load bearing capacity of a column. They are of four types. First column with both ends hinged. This is the standard column end condition. As a side note, effective length of a column is defined as the distance between points of zero movement. Effective length in this condition is equal to the length of column. Second column with both ends fixed. This is the strongest column end condition. Both ends fixed column carries maximum load and effective length for this condition is considered as half of total column length. Third, one end fixed and other end hinged. In this condition, one end of a column is stronger while the other end is very weak. Equivalent length for this end is 1 upon root 2. Fourth and the last condition, one end fixed and the other end free. This end condition makes column to bear the smallest load than all other end conditions. Column in such a condition is very weak. Equivalent length for this condition is 2L. Hence we first saw what columns and struts are and then went on to find out what the types of end conditions for columns are.