Structural behaviour of historic masonry cross vaults

The preservation of the architectural heritage presents one of the greatest technical challenges due to the complexity of the geometry of the structures, the variability of the material used or the loading history of the buildings. The knowledge of their pathology and collapse modes become therefore essential for the planning of structurally compatible and economic conservation programmes. In the case of gothic cathedrals, masonry cross vaults play a fundamental role in the roofing scherne and they are very sensitive to deformations imposed by failure of the system that contains their lateral thrusts. An experimental and theoretical study for the assessment of the safety of cross vaults is presented in this thesis. The case study is based on an aisle vault from the partially collapsed Abbey Church of Holyrood, Edinburgh. A replica ill 1/4-scale was built reproducing this ribbed vault, which has straight vertices and was made of rubble masonry. Initially, dead weight was applied to study the elastic response of the structure under service conditions. The effect of some parameters that are the source of uncertainty in the behaviour of historic buildings (load distribution, stiffness of the groins, support conditions, height of the spandrel fill) upon the deflections and strain distribution of the structure has been investigated. Finally, the abutments were allowed to move and the behaviour of the vault was assessed by correlating the deflections and strains recorded with the crack pattern that developed. Failure was reached when a sufficient number of fracture lines was formed, transforming the structure into a mechanism. Finite Element (FE) models were developed to simulate the behaviour of tile vault. The material properties required (stress/strain relationship and flexural strength) were established by wallette tests under four-line loading. The response to dead weight was studied in tile linear elastic range and the influence of tile groin geometry and tile Support conditions, among other features, were also investigated. In the course of the movement of the abutments, the formation of the fracture lines was simulated with a smeared-crack approach. The initial continuous FE model was further modified to concentrate failure at the weaker mortar joints. The sensitivity of the solution to some of the parameters examined earlier was investigated. The degree of safety of the structure was also evaluated with a limit state analysis. The analytical study of historic constructions is highly influenced by complicated interactions of a variety of factors and suggestions for further research are given based on the findings of this project