Friction as a geometric constraint on stereotomy in the minimum thickness analysis of circular and elliptical masonry arches

Friction is much needed for the equilibrium of masonry arches as it transfers load between the voussoirs. In this paper, applying an analytical formulation of the problem, the angle of friction as a geometric constraint on the stereotomy (bricklaying pattern) is investigated to find the possible range of minimum thickness values of circular and elliptical masonry arches under static loads based on the lower bound theorem of limit state analysis. The Heymanian assumptions regarding material qualities are adopted; however, limited capacity in friction is accounted for. It has been shown earlier that considering stereotomies a-priori unknown, a considerably wide range of minimum thickness values is obtained for fixed loading and global geometry conditions. It is found that a stereotomy constrained by an angle of friction, characteristic of masonry, renders the effect of stereotomy on the minimum thickness value negligible because the range of minimum thickness values is significantly reduced in this case. Hence, the present study ultimately justifies the intuitive assumption of radial stereotomy, widely used in the literature, whenever the safety of masonry arches is studied.