Homogenization of rammed earth walls under changing environmental conditions

Construction with rammed earth walls is a technique used for the construction of structures that has been increasing and by its nature requires in-depth knowledge due to the exposure of its materials (soil) to environmental factors, such as precipitation and solar radiation. This causes its structural elements to experience humidity fluctuations that affect the soil that constitutes them, resulting in a structure built with a material with heterogeneous properties, a fact that makes it difficult to understand its behaviour. The use of simulations in numerical models has helped to understand the internal dynamics of these elements. However, these procedures can present challenges in model construction and can also be computationally expensive, depending on the complexity of the model. In this context, the present research focuses on examining the behaviour of rammed earth walls against seismic action, when despite being made up of a single material, its composition is considered heterogeneous due to the humidity variations inherent to its exposure. Next, these models were subjected to a homogenization process of its properties using the Hashin and Shtrikman homogenization bounding theory. The objective is to find equivalent properties that facilitate the analysis of structural behaviour, assuming the homogeneity of the material. This homogenization process was extended to all parameters defined within the Pressure Independent Multi-yield material model employed in OpenSees, encompassing shear modulus, bulk modulus and density. As a result, applying Hashin and Shtrikman's upper bound to homogenize rammed earth walls produces remarkably similar results to those obtained using simulations of heterogeneous walls. This research provides valuable insights to understand rammed earth wall homogenization techniques and their behaviour, with important implications for their design and analysis.