Influence of the displacement of the supports on the collapse behavior of masonry semi-circular arches

Displacements of the supports affecting masonry arch systems and vaulted structures can determine a condition of collapse because of gradual changes in geometry. The paper presents an experimental study for the evaluation of the magnitude of the horizontal displacements of the supports that can be sustained by the masonry structure subjected to its self-weight before collapse. To this aim, both the arch prototypes and testing machine have been designed ad-hoc and realized by means of the use of the 3D printing technique. Two semi-circular configurations of the arch have been studied. The first one is a 1:2 scale version of the arch system studied by Ochsendorf in 2002 and characterized by a mean radius of 110 mm, a number of voussoir equal to 16 and a thickness-mean radius ratio equal to 0.23. The second configuration, defined by the same values of mean radius and number of voussoirs and by a higher thickness-mean radius ratio, equal to 0.3, has been set to investigate the effect of the slenderness on the behavior of the arch. The effect of the displacement of the supports on the stability the arch has been investigated in terms of collapse mechanism, evolution of the position of the hinges and ultimate displacement capacity. A comparison of the experimental outcomes has been also performed with numerical results obtained with a tool previously developed by the same authors in the framework of the rigid in compression no tension model for the masonry material and based on the approach of the kinematical theorem of the collapse state.