  This paper presents an automatic approach for the evaluation of the plastic
load and failure modes of planar frames. The method is based on the generation
of elementary collapse mechanisms and on their linear combination aimed at
minimizing the collapse load factor. The minimization procedure is efficiently
performed by means of genetic algorithms which allow to compute an approximate
collapse load factor, and the correspondent failure mode, with sufficient
accuracy in a very short computing time. A user-friendly original software in
the agent-based programming language Netlogo, here employed for the first time
with structural engineering purposes, has been developed showing its great
versatility and advantages. Many applications have been performed both with
reference to the classical plastic analysis approach, in which all the loads
increase proportionally, and with a seismic point of view considering a system
of horizontal forces whose magnitude increases while the vertical loads are
assumed to be constant. In this latter case a parametric study has been
performed aiming at evaluating the influence of some geometric, mechanical and
load distribution parameters on the ultimate collapse load of planar frames.
