Numerical Analysis for the determination of Stress Percolation in Dry-Stacked Wall Systems

This paper comprises a portion of a PhD study concluding on the potential use of a new mortarless and modular masonry system by taking into consideration the outcome of a multidisciplinary study including aspects of experimental, numerical and analytical investigations in relation to a practical and economical development of modular load-bearing dry-stacked masonry systems. Different forms of interlocking masonry elements have been modelled and optimised thermo-mechanically. Full-scale masonry walls were assembled and tested experimentally under compressive, flexural, shear, cyclic and long term loads. The overall structural behaviour was compared to conventional masonry systems such as hollow and shuttering blocks. The investigations showed overall relative high structural performances for the developed dry-stacked elements. The effect of dry joint interfaces was extensively investigated experimentally and numerically under FE analysis. Based on the experimental observations, a numeric-analytical failure mechanism of the dry-stacked masonry structure is anticipated under axial and flexural loading. The structural investigations and engineering processes are completed by the development of a package of dry-stacked units consisting of interlocking modular masonries and an accompanying array of various other precast parts. This confirmed the practical issues and solutions towards the exploitation of the developed dry-stacked elements for the construction of ready-to-build, modular and load-bearing walls.
The portion of work presented herein proposes a new numerical technique for the determination of stress-percolation in dry stacked load-bearing structures. The model is developed in three steps under a numerical computing environment. First, based on geometrical properties of the dry-stacked elements and with a linear-elastic material behaviour, the load percolation and intensity in dry-stacked masonry walls is determined. In a second step, a phenomenon known as a plastic accommodation which accompanies the redistribution of the stress percolations, is incorporated in the model. This enables the understanding of the evolution of the stress percolations in the post-elastic phase, which is crucial for the determination of the load capacity and stability of the structure in function of an increased external load. This paper also supports the better understanding of early fissuring in dry-stacked masonry structures which has an important influence on the overall stability of the structure. Finally, in a third step, the improvement of dry-stacked structures is pursued by further analysis of the results obtained through the algorithm.
This paper represents a new tool for investigating the localized and randomly defined internal stress distribution induced by external compression forces on dry-stacked structures. Furthermore, the algorithm illustrates that experimental investigations on dry-stacked systems may only give real indications on the load capacity of the structure, when the number of joint interfaces and height to length ratio of the block is respected and that results of experimental investigations on reduced prism specimens may not be extrapolated to full sized walls as they may over-evaluate the effective loaded masonry sections and therefore the overall load capacity.