The equilibrium of cloister masonry vaults, treated as composed of unilateral
material in the sense of Heyman, is the topic of the present work. For such
a material, the safe and the kinematic theorems of limit analysis can be
employed to detect equilibrium and nonequilibrium. In the spirit of the safe
theorem, the structure is stable if a statically admissible stress field can
be detected. On allowing for singular stresses, here we consider statically
admissible stress fields concentrated on surfaces or lines lying inside the
masonry vault. Such structures are unilateral membranes, whose geometry is
described a la Monge, and the equilibrium of them is formulated in Pucher
form, that is, in terms of the so-called projected stresses over the planform
. The
problem, under purely parallel loads, is reduced to a single partial differential
equation of the second-order, in two space variables, where the shape function
and the stress
function
appear symmetrically. The unilateral restrictions require that the membrane surface
lies in
between the extrados and intrados surfaces of the vault and that the stress function be
concave. In the present work, by starting with a sensible choice of a concave stress function
, the transverse equilibrium
equation is solved for
by imposing suitable boundary conditions. A cloister vault of
Palazzo Caracciolo diAvellino, a XIV century building located along
via dell’Anticaglia in Naples, is the
case study. For two load conditions, membrane surfaces and geometrical safety factors
are identified.
Keywords
limit analysis, vaults, masonry-like materials, Airy's
stress function