Résumé

Transmission photoelasticity on scale models is shown to disclose the stress distribution within dry masonry walls. This distribution is found to be complicated by unilateral joints between elements, where ‘randomness constrained within a geometrical scheme' of contact points occurs, so that stress percolation results highly localized, evidencing ‘unloading islands' in a ‘stress stream'. These findings are theoretically explained in Part II of this paper from both micromechanical and continuous modelling perspectives.