Limit analysis of masonry arch bridges through an adaptive GA-NURBS upper-bound approach

This paper investigates the application of a fast and reliable NURBS-based kinematic limit analysis approach for the assessment of the collapse behaviour of masonry bridges. This approach relies on the description of the geometry of the bridge structure by means of NURBS approximating functions. Starting from the known geometry, an assembly of rigid bodies can be generated, composed by very few elements which still provide an exact representation of the original geometry. The main properties of masonry material are accounted for through homogenisation and an upper-bound formulation for the limit analysis of the obtained mesh is devised. The approach is capable of accurately predicting the load bearing capacity of masonry bridges with arbitrary geometry and load configuration, provided that the initial mesh is adjusted by means of a suitably meta-heuristic approach (i.e., a genetic algorithm) until element edges correctly approximate the actual yield lines of the collapse mechanism.