Some Consideration on out-of-plane collapse modes of masonry

n this paper the problem of out-of-plane collapse of masonry walls under vertical and horizontalloads is addressed through the review of ancient building rules and the study of the European (Eurocode 6 and 8)and new Italian seismic codes on unreinforced masonry buildings.The limitations of the analysed seismic codes and the empirical geometrical rules of ancient constructors arecompared with the results of some structural analyses carried out on rectangular masonry panels with differentslenderness h/s, aspect ratio h/b (height/width) and boundary conditions. In particular, the analyses have beencarried out both with the limit analyses and non linear FEM analyses with Abaqus computer code.The results of these parametric analyses show that the respect of the seismic codes limitations on the geomet-rical slenderness h/s allows to implicitly have a minimum resistance to out-of-plane collapses of the masonrywalls.A proposal is made to overcome the unjustified provisions of some codes which do not allow to have distanceamong orthogonal walls larger then 7 m.