EVALUATION OF HISTORICAL STONE STRUCTURES UNDER EXTREME ACTIONS USING RIGID SOLID DYNAMICS METHODS. CASE STUDY: THE ALCÁNTARA BRIDGE, SPAIN

The conservation of historical masonry structures must include resistance to dynamic actions, such as earthquakes, explosions, impacts, among others. These actions typically require the use of complex nonlinear models. In addition, these models present additional difficulties when dealing with masonry structures, limiting the applicability of the calculation models and finite element programs. The research focuses on developing numerical models-formed by blocks-that fully consider rigid solid dynamics (3D), considering the normal and tangential nonlinear behaviour at the contact zones between all blocks themselves. The solution was performed in an explicit time-domain for dynamic analysis due to the extreme nonlinearity. One of the practical problems to solve here was related to the construction of the numerical model itself through the geometric placement of the different stone blocks, each with its shape and orientation. To solve this issue, scripts were written in Python that allowed systematising and facilitating the entire generation of models with thousands of blocks. As a representative case study, the central pier of the Alcántara Bridge –located in Cáceres, Spainwas used. The bridge is an iconic work of Roman engineering (2nd century) with enormous heritage and historical value. After subjecting the central pier to a seismic action at the base, the results validated the expected collapse mechanism in this structure, characterised by the expulsion of the stone blocks and the progressive collapse of the internal infill. It is thus demonstrated that nonlinear modelling of masonry structures with rigid blocks can be an effective alternative to determine the seismic capacity of historic stone structures.