Case study of the failure of a cross vault: Church of Holyrood abbey

The church of Holyrood Abbey, in Edinburgh, collapsed in 1768 after an inappropriate intervention in the nave vaults. This resulted in excessive lateral thrusts, which could not be contained by the existing buttressing systems, causing progressive instability of the lateral walls. This effect was studied on a lateral cross vault of the church. A replica in 1:4 scale was built and tested initially under service loads and subsequently until collapse due to movement of the two front abutments. Analysis of the model was carried out with the finite-element program ABAQUS. The resulting behavior demonstrated the significant load-bearing capacity of the structure under service conditions and its high sensitivity to imposed changes of the geometry. Although the tensile stresses exceeded the flexural strength at the vertices and the abutments, the collapse was dominated by the membrane tensile failure at the groins, hence both the geometry and condition of this area are critical for the safety of the vault. The results of this study can improve the assessment and thus help in the preservation of many important Gothic and neo-Gothic churches.