Benchmark problems from the AISC 2010 Specification for Structural Buildings (commentary, page 16.1-276) have been reproduced in ETABS. The intention of AISC benchmark problems is to indicate whether or not an analysis software is capable of performing rigorous second order analyses which include P-Δ and P-δ effect.
ETABS captures both sources of nonlinear geometry with great accuracy, well within the 3% and 5% limitation of AISC. This capability is validated in the benchmark-problem results, shown below, in which a column is divided into segments and subjected to compression.
Figure 1 - P-δ response
Figure 2 - P-Δ response