Calculation of Effective Lengths of Stepped Columns

Travelling cranes are frequently used to move heavy loads in industrial buildings. To accomplish a general movement, the crane traverses a crane bridge, which in turn moves on rails along the length of the building, supported by the main building columns. Designers frequently choose stepped columns, with the wider lower section serving a dual purpose: (a) to support the crane rail and (b) to provide the necessary strength to support the extra load from the crane. The design of the stepped columns is time-consuming and complicated. Effective lengths, which must be calculated for each segment, depend upon the following: the end fixity types at the two ends, the ratio of segment lengths, the ratio of the segment inertias, and the ratio of the applied axial loads applied at the top of the column and at the stepped levels.