Stochastic Simulation of Clay Brick Masonry Walls with Spatially Variable Material Properties

In the assessment of existing masonry structures, a high variability of material properties can be observed. The variability is also present within a single wall, which raises the question of how this spatial variability influences the load-bearing capacity and the reliability of an assessed masonry wall. With regard to reliability, lower quantile values of the load-bearing capacity are decisive. For this reason, the influence of spatial variability on the probability distribution of the load-bearing capacity has to be known. In this paper, clay brick masonry walls in compression are investigated by Monte Carlo simulations utilising a nonlinear finite element model. For the validation of the finite element model, experimental investigations of the stress redistribution capability of masonry walls with weak spots were carried out. The numerical model follows a simplified micro-modeling approach with unit-to-unit variability of the material properties. Results of the stochastic simulations are shown for varying wall length, slenderness and coefficients of variation of the material properties. The obtained statistical distributions of the load-bearing capacity are evaluated with respect to acceptable design values for ensuring structural reliability. It is shown that spatial variability leads to a reduction of the mean load-bearing capacity, but the overall variability of the load-bearing capacity is much smaller than that of the spatially varying material properties. Compared to an approach assuming homogeneity within the wall, the consideration of spatial variability leads to an increase of suitable design values.