Material and Material Model
In contrast to the materials such as concrete or steel, there are no preset materials for masonry as there are not many combinations of bricks and mortar in this case. Therefore, you have to create a new material for each material combination. However, you can always use it in future again. It is also possible to change the created combinations later, if required.
In addition to the definition of the material and the material properties, it is necessary to assign the relevant material model to this material. For example, the material model included in RF‑MAT NL is set to "Isotropic Masonry 2D" in order to adequately consider the failure at tension and the corresponding crack formation. You can specify the limit tension stresses for the failure at tension separately as parallel and perpendicular to the joint in accordance with the standards. If you set the limit tension stress to zero, a value of 1 ∙ 10-11 N/mm² will be applied in the calculation for stability reasons. Therefore, minimum tension stresses may occur even without specifying the limit tension stress.
Modeling and Evaluation
As an example, a compact reinforced wall surface is modeled and evaluated according to [1] :
The vertical load is distributed on the entire wall length. The same applies for the horizontal load, otherwise a singularity would occur on the load application point due to the concentrated load introduction. This could lead to failure of the model, because the allowable tension stresses would be exceeded at this node and would crack completely.
The deformation analysis may already indicate the distribution of internal forces and stresses.
The stress analysis of the wall after the nonlinear calculation shows that the allowable tension and compression stresses have been met.
In the case of exceeding the limit stresses in the wall or the failure of the masonry wall, no convergence is achieved. Therefore, it is necessary to adjust the material or the dimensions. For example, if you increase the wall thickness, the resulting tension stress can be distributed over a larger area so the load-bearing resistance will be improved.
The modeling of masonry described in this article and the stress analysis in the surfaces cannot take the place of the masonry wall design. However, it can be concluded what materials and dimensions are required for further analysis.