Load Carrying Capacity of Simple Composite Columns

A computer program based on a finite difference method of analysts has been developed for determining load deformation relationships to failure for pin-ended eccentrically loaded steel columns encased in concrete. The solutions obtained are the most accurate yet determined and take into account both the linear and nonlinear ranges of the two materials; comparisons have been made with the results of tests on both small and full scale columns. Quantitative Information obtained from the computer program has been used to examine critically existing and other likely design criteria applicable to columns of both British Standard and Universal sections. It is demonstrated that the simple interaction formula used in some design codes to determine permissible combinations of axial force and bending moment, leads to variations in load factor which are irrational. Consideration is also given to the control of the incidence of cracking of concrete under working conditions.