The P-Delta Analysis is performed by loading the modified frame with each of the column combinations. The modification of the frame is done by finding the disturbed frame model under the load. To do this, frame nodes are displaced by the value of the displacement from the previous load and loaded again with the load from the same load combination. This process is performed until the number of iterations reaches 5 or the difference of the displacement at the top of the column (column bottom is fixed) between the previous and present iterations is within 5%. Several implementation considerations are as follows:

Moments amplified by P-Delta are used for column and footing designs in the current version of Substructure.

Impact factor of live load is applied to the final results.

If the cracking effect must be taken into account in column design with P-Delta analysis, you must specify the reduced moment of inertia for the column. Substructure does not automatically consider the cracking effect.