Medieval Arch Bridges in the Lanzo Valleys, Italy: Case Studies on Incremental Structural Analysis and Fracturing Benefit

After presenting a historical overview concerning the masonry arch design, this article proposes a computational procedure that allows the capture of the arch-damaging process, which takes place when the conditions assessed through linear elastic analysis are no longer valid and before the set-in of the conditions established by means of limit analysis. This evolutionary analysis of the fracturing process is then applied to three medieval masonry arch bridges located in the Lanzo Valleys (Italy). Through damage assessment, the present work shows how the arch thrust line is affected by crack formation and the internal stress redistribution; it also shows that the maximum admissible load evaluated by means of linear elastic fracture mechanics is greater than the load predicted by the theory of elasticity. Such an increment in terms of maximum admissible load can be defined as the fracturing benefit, and it is analogous to the plastic benefit of limit analysis.