Assessment and restoration of a masonry dome in the cathedral of Tortosa enclosure

摘要

In April of 2011, one of the masonry domes of the cathedral of Tortosa enclosure (Catalunya, near Barcelona) suddenly broke. This paper presents the restoration process of this XVIII century dome, exposing the evolution of the rupture and its causes, the analysis of the cracking process and the numerical approaches developed to determine the restoration techniques. After an initial constructive assessment, the equilibrium conditions of the structure are analysed. Traditional graphical methods are used complementary to a 3D survey by finite elements (FEM), using the free software Salome-Meca 6.3. Through the models developed, it is possible to relate the tensional states and the deformations of the shell with the real breaking process of the dome. The assessment concludes that the dome does not break because of a failure of the material by tensional problems, but does because of an asymmetric load which causes the formation of collapse joints. This load was a consequence of the breaking of a beam which held the combined load of the roof and part of the lantern. The intervention consisted of restoring the shell of the dome with traditional techniques, "guix i estopd", and also reinforcing the bearing capacity of the structure to support the weight of the big lantern and also the roof.