Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)


Civil Engineering


Dr. S. Pietruszczak


This thesis presents a comprehensive approach to numerical modelling of the nonlinear behaviour of structural masonry. Masonry is a heterogenous material, which displays orthotropic symmetry. The anisotropy effects are described here by incorporating a set of distribution functions specifying the directional dependence of material properties.

In the first part, a macroscopic failure criterion for structural masonry is proposed. This criterion is derived within the framework of the critical plane approach. First, a general discussion is provided examining the performance of this framework within the context of both classical linear and nonlinear criteria. Subsequently, a bi-linear form of failure criterion for strucutral masonry is proposed. Extensive numerical study is performed examining the behaviour in biaxial compression-tension and compression-compression regimes for different orientations of the sample relative to the loading direction. The results are compared with the available experimental data.

In the next part, the results of a 3D seismic analysis of the masonry walls of a power substation building - typical of those constructed in the elastic range, assuming orthotropic material properties, and the admissibility of the stress field is assessed based on the proposed failure criterion. A numerical study is performed examining the effect of different reinforcement strategies.

The focus of the last part of this thesis is on the description of progressive failure in structural masonry. A continuum formulation is developed here which is applicable to a representative volume comprised of a large number of units interspersed by mortar joints. The framework defining the conditions at failure when employing the critical plane approach is extended to model the inelastic deformation process. This is accomplised by incorporating a multi-laminate approach in which the average response is derived from sliding/separation characteristics along a set of randomly distributed planes. The localized deformation is descrived by considering a structured medium comprising the intact masonry intercepted by a distinct macrocrack. Extensive numerical simulations are performed examining the response of brickwork in compression/tension regimes at different orientations of the bed joints relative to the loading direction. A boundary-value problem which involves an inelastic finite element analysis of a bearing masonry wall subjected to in-plane loading is also studied.

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