Three-dimensional discrete element modelling of rubble masonry structures from geospatial data

Abstract

This paper presents a framework for the three-dimensional structural analysis of full-scale, geometrically irregular discontinuum structures such as rubble masonry, directly from geospatial data. A convex decomposition algorithm is adopted, whereby a watertight mesh is subdivided into so-called voronoi blocks which approximate the anisotropic nature of the rubble masonry for structural analysis. The proposed “Voronoi4DEM” framework was implemented to assess the structural stability of the southwest leaning tower of Caerphilly Castle in Wales, UK. Simulations were performed with the three-dimensional computational software 3DEC, based on the Discrete Element Method (DEM) of analysis whilst each voronoi block of the rubble masonry was represented as a rigid, distinct block while mortar joints were modelled as zero thickness interfaces which can open and close depending on the magnitude and direction of the stresses applied to them. The innovation of this framework lies in the specific geometric strategy which approximates the random nature of discontinuous materials at a blockbased level (such as rubble) with sufficient accuracy, whilst vastly reducing computational times. Consequently, the approach can simulate the highly complex behaviour of rubble masonry structures with a high degree of efficiency, geometric accuracy, and automation. It is anticipated that the methodology proposed here to enable unprecedented high-level numerical modelling (block-based numerical modelling) of full-scale rubble masonry structures with, until now, unemployed techniques such as the DEM.