Analysis of masonry pointed arches on moving supports: A numeric predictive model and experimental evaluations

In this paper the topic of the vulnerability assessment of masonry arches on moving supports is analyzed. A novel numerical procedure for detecting the collapse mechanism and computing the limit support movement was developed by the authors and herein applied to the case of pointed arches, on which few studies are available in the literature. The proposed procedure is conceived as an algorithm that identifies the set of three hinges that could open in the arch due to an infinitesimal support movement, exploiting the laws of combinatorial analysis. Then, in order to identify the solution, the unique three hinge pattern by which the structure is balanced and congruent, a kinematic and an equilibrium test were carried out on the arch. The limit value of the support movement is successively computed by a step by step procedure that increases the support movement, draws the modified configuration of the arch and computes the line of thrust passing through the three hinges. When the line of thrust becomes tangent to the extrados or intrados of the arch in further joints, the collapse mechanism is detected together with the limit value of the support movement. This procedure represents a progress of the state of the art since it avoids the use of optimization techniques required in limit analysis, with a consequent reduction of the algorithm complexity. Furthermore, in-scale pointed arch models are performed by the authors and tested subject to a horizontal movement of the left impost. Numerical models of such arches are analyzed using the procedure above and results are compared to the experimental outcomes. Finally, to investigate the effects of the arch geometry, the numerical results of pointed arches are compared to the results of circular arches with same span, thickness and angle of embrace.