Parametric study on the seismic vulnerability of unreinforced masonry cross-vaults

Abstract

This dissertation focuses on the seismic response of the cross-vault, a curved masonry structure typically roofing over impressive heritage buildings, and which extensively varies in form and geometry. This study intends to investigate, within the local context, the seismic vulnerability of unreinforced masonry cross-vaults of varying geometry and constructional configurations. A numerical macro-modelling strategy is adopted, and through parametric variation, a set of fourteen numerical models were generated in the HiStrA software. The parameters primarily simulate cross-vaults of different aspect ratios on plan, the addition of diagonal ribs and cross-vaults in aggregate. The seismic performance of the models is assessed through a non-linear static pushover analysis, providing results in the form of capacity curves, observable deformation and lateral deflections. On account of a comparative analysis, the findings established that a rectangular cross-vault characterised by an elliptical arch geometry, is stiffer and offers more resistance to sway as opposed to a square-plan vault. The results additionally shed light on the differences and similarities between local and global cross-vault behaviour. In all instances, the observed damage clearly indicates the four-hinge formation as the central collapse mechanism, and the results conclude that despite being complex three-dimensional curved structures, cross-vault behaviour is remarkably similar to that of a two-dimensional masonry arch. Apart from confirming that masonry compressive strength is irrelevant in lateral stability of cross-vaults, the findings suggest the notion of quasi-ductile behaviour, despite masonry being a brittle material. Thus, this study concludes that geometric and constructional parameters evidently influence the response of unreinforced masonry cross-vaults when subjected to seismic loading. In this regard, the understanding of the effect of different forms and global configurations could translate into the identification of suitable retrofitting techniques as a means to safeguard heritage buildings in the event of an earthquake.