A large class of analysis methods has been developed during the last century for the
study of masonry structures. Among them, the so-called unilateral no-tension
model plays a fundamental role. Starting from the pioneer papers by Heyman
in the second half of sixties, a new definition of the safety factor based on
the equilibrium of the masonry structure as a no-tension body has been
considered. The safety of the structure is mainly determined by its geometry
rather than its material strength. The funicular analysis largely used in the
19th century has been improved in light of Heyman’s approach to obtain
computational methods based on lower-bound solutions. Heyman’s hypotheses are
the basis of the rigid no-tension continuous approach presented and applied to a
barrel vault with lunette in the San Barbaziano church in Bologna. The
masonry vault is modelled as a membrane (thrust surface) subjected to
compressive stresses only, contained within extrados and intrados surfaces, and
carrying uniform applied loads. The geometry of the unilateral membrane,
described as an unknown smooth surface, and the associated admissible stress
field are determined via a concave stress function necessary for equilibrium
and unilateral constraints fulfillment. Special attention has been devoted
to the singular stress field arising in the curves at the intersection of the
vaults.