Masonry arch bridges form a substantial part of existing bridges and play a critical role within the European transportation system. Moreover, historical masonry bridges belong to the architectural heritage and represent a tangible experience of past construction technologies that should be safeguarded. Many of these structures are located in seismic prone regions and/or in areas subjected to floods and hydrogeological instability aggravated by climate change. Thus besides increasing traffic loading, they can be subjected to extreme environmental actions which may potentially lead to bridge failure causing severe disruptions and major economic and cultural losses. In this regard, realistic structural assessment under extreme loading conditions is a current challenge for the structural engineering community which may prevent future failures by identifying structures in critical conditions, prone of suffering extensive damage from extreme events, and in need of strengthening. In general, the response of masonry bridges is very complex as it is determined by the interaction between different structural and non-structural parts. However, current modelling strategies are formulated following limit analysis principle or simplified 2D finite element descriptions which disregard the masonry anisotropy and the potential activation of spatial, global or local, failure mechanisms of the bridge. Finite element mesoscale approaches enabling an explicit representation of masonry bond, where mortar joints and masonry units are modelled separately, can provide accurate predictions of realistic masonry bridges under different loading conditions representing complex cracking patterns, including transverse cracks due to differential settlements induced by pier scour or earthquakes. However, as this advanced strategy requires superior computational resources and specialist users, it is not suitable for practical assessments.
The RAMBEA project has developed an innovative methodology for realistic analyses of historical masonry bridges under extreme environmental actions. It is based upon a two-scale FE description of masonry components of the bridge combined with contact elements to connect masonry arch and external walls to the continuum backfill domain. The developed modelling strategy allows a reliable description of the anisotropic micro-structure of masonry, considering the cohesive and frictional characteristics of the masonry joints, including the degradation of strength and stiffness under cyclic loading. The model enables realistic predictions of complex, three-dimensional cracking patterns while allowing for computational efficiency. Moreover, the RAMBEA project has developed a practical and robust calibration procedure based upon the mesoscale mechanical properties of bricks and masonry joints which can be easily obtained by non-destructive in-situ tests, suitable to be used for historical constructions and cultural heritage assets.
The developed methodology has been applied to real case studies, where the numerical predictions provided by the novel efficient strategy have been compared against available experimental data or the numerical results obtained employing high-fidelity mesoscale descriptions of the analysed bridge structures. The main outcome of RAMBEA is thus an efficient and accurate numerical approach for the structural assessment of historical masonry bridges subjected to complex loading conditions corresponding to extreme natural events.
