Influence of spatially variable material properties on the resistance of masonry walls under compression

During their assessment, existing masonry structures often reveal a high variability of their material properties. Since this variability is also present within a single wall, the influence of this spatial variability of the material properties on the wall resistance is of major interest. First, experimental investigations on clay brick masonry walls with local weaknesses under compression loading are presented. The results of these experiments serve to validate a finite element model developed to study the influence of spatially variable material properties on the resistance of masonry walls under compression. The model follows the simplified micro-modelling approach and allows for a unit-to-unit variability of the compressive strength and the elastic modulus of masonry. The finite element model is then utilised within Monte Carlo simulations to investigate the resulting probability distribution of the wall resistance for given distributions of the material properties. Finally, parameter studies are conducted to examine the influence of the coefficient of variation of the material properties, the spatial correlation of the material properties, wall length, and wall slenderness on the resulting distribution of the resistance. The studies demonstrate that spatial variability leads to a decrease in the mean value of the wall resistance. However, the resulting variability of the resistance is much smaller than the input variability of the material properties. Considering the spatial nature of the variability can thus lead to higher design/assessment values of the wall resistance and, hence, a positive effect on structural reliability.

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