Effective iterative algorithm for the Limit Analysis of truss-frame structures by a kinematic approach

A former algorithm of Limit Analysis (LA) at the continuum mechanics scale by a kinematic, upper-bound approach is here re-interpreted in the realm of LA of large-scale 3D truss-frame structures and effectively implemented toward fast and convenient collapse load multiplier and mechanism evaluation. First, the algorithm is described in its iterative design, and convergence is demonstrated. Some initial applications to truss-frame test structures under bending and torsion are also discussed. Then, the algorithm is successfully applied to two benchmark multi-story frames. It is shown that very consistent and quick evaluations of the collapse characteristics are obtained by this direct method, in comparison to those provided by alternative classical mathematical programming approaches and much expensive evolutive step-by-step solutions of the whole structural elastoplastic response. The algorithm shows a superior performance, with the kinematic multiplier truly precipitating from above on the collapse one, in very few iterations, with a consistent associated estimation of the plastic collapse mechanism.