New computational Limit Analysis approaches for structural optimization problems

In this paper, two recently developed algorithms for the computational Limit Analysis of large-scale 3D truss-frame structures are outlined as useful tools for structural design and optimization purposes. Specifically, they are developed toward characterizing the structural collapse state, which can be considered in selecting the optimum geometrical configuration within appropriate form-finding procedures. The first algorithm, starting from [1], is able to trace a fully exact evolutive piece-wise linear elastoplastic response of the structure [2], up to plastic collapse, by reconstructing the true sequence of activation of made-available plastic joints (as a generalization of plastic hinges). The second algorithm is based on a kinematic iterative approach [3] and is able to determine collapse load multiplier and plastic mechanism in subdued computational time [4]. A rather impressive performance is achieved, in truly precipitating from above on the collapse load multiplier, by rapidly adjusting to the sought collapse mode, in very few iterations. The two algorithms could be conceived separately or all together, based on their own peculiarities, to set down a very efficient procedure toward ruling structural optimization problems based on form-finding quests relying on LA interpretations and concepts.