Andrea Chiozzi1, Nicola Grillanda1, Gabriele Milani2, and Antonio Tralli1
1)  Department of Engineering, University of Ferrara
Via Saragat 1, 44122 Ferrara, Italy
e-mail: {andrea.chiozzi, nicola.grillanda, antoniomichele.tralli}
2)  Department of Architecture, Built Environment and Construction Engineering (ABC)
Technical University of Milan, Piazza Leonardo da Vinci 32, 20133 Milan, Italy

Keywords: Masonry, Bridges, NURBS, Limit analysis.

Abstract. In this contribution, the collapse behavior of masonry bridges is numerically analyzed by means of a fast and reliable limit analysis approach based on the upper-bound theorem. This approach relies on the description of the geometry of the bridge structure and backfill by means of NURBS approximating functions. A rigid body mesh starting from the assigned geometry can be generated, which is composed by very few elements still providing an exact representation of the original geometry. The main properties of masonry material are accounted for through homogenization and a kinematic formulation for the limit analysis of the obtained rigid block assembly is derived. 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 failure mechanism. The approach proves to be both accurate and computationally inexpensive when compared to standard nonlinear finite element analyses and other more sophisticated numerical procedures proposed in the literature.