Department of Civil Engineering, University of Wales, Swansea, UK

It is well known that the strength of masonry structures is affected, among other things, by material inconsistencies of its main constituents, that is masonry units and mortar [1,2,3} ami the quality of the workmanship [4,5,6,7j used in the construction phase. This has long been recognised by Codes of Practice such as BS 5628 [8] and Eurocode EC6 [9] which have introduced a partial factor of safety ymfor the design strength of masonry to cover these variations. The exact mechanism and the extent of reduction in the strength of masonry does not, however, appear to have been scientifically investigated, and the provisions for ym in both are empirical and generally based on past experience only. The aim of the study reported here is to examine and quantify the effects of the various causes of the reduction in the strength of masonry due to workmanship quality through the application of a finite element model. Here, masonry is treated as a composite material with masonry units and mortar joints forming its constituents. Each constituent is assumed to behave as an isotropic linear elastic-brittle material. A two stage homogenisation (macro-modelling) technique, in which the constituent materials are smeared to form a homogeneous orthotropic material, which captures the average mechanical response of masonry was used in this study. Using this technique a number of tests were carried out on a masonry wall panel indicating how the workmanship qualities influence the overall strength of the panel whilst also identifying the. relative importance of each defect.