In-plane collapse behaviour of masonry walls with frictional resistances and openings

The paper discusses the limits of validity and applicability of a simplified procedure to assess the lateral capacity of masonry walls loaded in-plane. Limit state analysis is applied to masonry panels simulated as dry assemblage of regular blocks governed by static friction. The friction forces are calculated for various geometric conditions of inclination of cracks, and collapse load factors are computed by use of minimization routines. By consideration of how friction forces develop in relation to the relative shape factors of units and panels an upper and lower thresholds for the possible collapse load factor are identified and by comparison with a discrete element analysis is shown that they do bound the range of existence of the load factor. The procedure is then extended to walls with openings by considering the restraining effect of the spandrels.