Collapse behaviour of masonry arch bridges strengthened with an external post-tensioning system

Masonry arch bridges represent a significant portion of existing road and rail infrastructure and often require strengthening due to material degradation and structural damage. This paper evaluates the effects of an external steel cable post-tensioning system on the collapse behaviour of masonry arch bridges. A nonlinear kinematic analysis is employed to model and analyse the strengthened structure, accounting for the finite compressive strength of the masonry, the ultimate strength of the post-tensioning system and the possible failure modes. The mechanical model, developed in MATLAB, is validated against experimental tests conducted on a quasi-semicircular masonry arch model, representative of typical Italian railway bridges, which was strengthened with intrados-applied post-tensioning cables. Results highlight a significant improvement in load-bearing capacity and variations in collapse mechanisms induced by the strengthening system. Furthermore, this study introduces the vertical load-displacement capacity curve of a post-tensioned masonry bridge, providing new insights into its structural behaviour. • First numerical vertical load-displacement curve for post-tensioned masonry bridges. • Nonlinear kinematic model capturing the evolution of post-tensioning forces. • Numerical validation on scaled masonry arch bridge models. • Increased load-bearing capacity of masonry bridges through post-tension.