Collapse of Masonry Buttresses

Abstract

This paper investigates the collapse of masonry buttresses under concentrated lateral loads. A fracture forms at the collapse state, significantly decreasing the resistance to overturning. Conventional analysis assumes that a masonry buttress acts monolithically to resist lateral loads. The current paper demonstrates that this approach is clearly unsafe, and the possibility of a fracture at the collapse state must be considered in the design and assessment of masonry buttresses. By treating the masonry as a continuum, infinitely strong in compression, with no resistance to tension and no possibility for sliding, the writers demonstrate the form of the fracture and determine the critical failure load for typical buttress forms. This approach follows in the tradition of limit analysis of masonry structures as developed by Hey man. General methods are proposed for the overturning analysis of masonry buttresses, and calculation examples are provided. Finally, methods for evaluating the safety of existing buttresses are presented and discussed.

Procedural modeling of structurally-sound masonry buildings

“…A second validation test measured the maximum angle of ground tilt before an arch becomes infeasible. For an arch with 0.20 thickness/radius ratio, the critical tilt angle is 15.84 degrees [Ochsendorf 2002]. Our results match this value exactly for a 100-block arch.…”

The safety of masonry buttresses

“…When conducting research under Heyman at the University of Cambridge, Ochsendorf used a numerical approximation to obtain the surprising result that the fracture of a rectangular buttress was planar. This elegant demonstration of planar fracture was made known to the author in a private communication (Heyman, 2001) and in Ochsendorf's doctoral thesis (Ochsendorf, 2002). It was published in Spanish and English (Ochsendorf et al, 2003(Ochsendorf et al, , 2004 and, more recently, Ochsendorf and Lorenzi (2008) have contrasted previous studies of the fracture of buttresses with numerical models of block systems.…”

“…The collapse load F c can be calculated by statical considerations Figure 19. The earliest known consideration (Monasterio, c. 1800) of the fracture of buttresses and its effect on the stability of the vault-buttress system within vault theory (Huerta and Foce, 2003) Engineering History and Heritage 163 Issue EH1 The safety of masonry buttresses Huerta (Ochsendorf et al, 2004) giving a value around 30% less than the collapse load for the monolithic buttress.…”

As Hangs the Flexible Line: Equilibrium of Masonry Arches

“…The concept was first rigorously formulated by Moseley [1833] and an excellent mathematical treatment was offered by Milankovitch [1907]. The analytical solution for this concept has been defined more precisely as the locus of pressure points by Ochsendorf [2002].…”