B. CHIAIA (1) and C. CENNAMO (2)
(1) Department of Structural and Geotechnical Engineering, Politecnico di Torino, Italy
(2) Department of Design Knowledge, Seconda Università di Napoli, Italy
The main peculiarity of “irregular” and “sack” masonry, which are built by throwing irregular pieces of stone and mortar between two regular brickwork skins, is the chaotic pattern, which results in very high values of local stresses in the walls of the structures, which could easily exceed the strength limits, and eventually lead to the instability of the confining brick walls. Moreover, the chaotic infill is responsible for a peculiar internal stress flow that, as long as mortar deteriorates with ageing, resembles more and more the stress distribution in compressed granular matter.
This work investigates how the geometrical distribution of stones and brick pieces in chaotic masonry defines the characteristics of the stress flow. The topology of the networks of force chains, is strongly dependent on the shape and size distribution of the masonry pieces, and is affected by the pattern of contact points. Using a numerical particle flow approach, coupled with the tools of fractal geometry, it is possible to determine, the distribution of contact points, the stress distribution in chaotic masonry panels and the possible consequent fracture pattern.
Eventually, fractal geometry permits one to calculate the degree of disorder and branching in the stress flow networks, allowing the range of extreme stress values in the pseudo-continuum, to be quantified and so enables one to obtain useful hints for calculating the degree of safety in historical chaotic masonry.