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To date, most numerical simulations of masonry have been based on finite element continuum methods in which sophisticated and often-complex material models in conjunction with arrays of gap elements are used to account for the requirements listed
above. A more intrinsically satisfactory approach for masonry is to base the analysis on a series of discrete elements. This more natural approach can be used to represent ranges of masonry from completely intact buildings to piles of random rubble.
3. Discrete Element Technique.
a. The technique used to perform all the analysis in this study is the discrete element (DE) method. This is a development of the distinct element method (Cundall, 1971) in which the concept of individual elements being separate and reacting
with their neighbours by contact through friction/adhesion was first successfully applied to geotechnical and granular flow problems. Here elements were considered rigid but later developments (Munjiza et al, 1995) included the addition of element
deformations and fracturing, with some overlap with traditional finite element theory.
b. In the current investigation the DE formulation available in the explicit dynamic version of ELFEN (Rockfield Software Limited, 1998) has been used. Essentially three different approaches have been used for the non-linear analysis of masonry
each requiring different modelling approaches:
- Macro Blocks. The category where the joints between blocks have predominantly no strength and models the construction generally found in historic structures.
- Brittle Material. This is where the masonry blocks and joints have predominantly similar strengths, as is more likely in modern forms of construction or where masonry is weak and random.
- Brittle Macro Blocks. Here the macro block approach is used with brittle materials thus permitting a blocky representation to fracture into further parts.
The first two approaches have been investigated for shear wall applications to investigate the sensitivity of seismic resistivity to mortar properties (Brookes, Mehrkar-Asl, 1998).
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