Inverse analysis of straw bale mechanical parameters in load-bearing structures based on a finite element model

Abstract

Scientific and practical research into alternative building materials is of high importance in terms of sustainability and ecology. Many variables have to be taken into account when using straw bales as load-bearing structures in residential buildings. The main problems are the lack of information on the mechanical properties of this material and its potential high variability. The development of numerical FEM models based on accurate experiments can help to better understand the behaviour of this material. The main objective of this paper is to present a simplified isotropic model of straw bales based on measured data from a laboratory experiment, which will facilitate the preparation and evaluation of further future experiments. Already partially published data of compression tests of load-bearing straw bales were analysed. Using an automated algorithm, an estimate of the elastic modulus of the bale was determined, and inverse analyses were performed using accurate FEM numerical models based on similarity to the force-deformation diagram. In all experiments, it was found that the ideal combination is elastic modulus at 20% load and Poisson's constant of 0.2. From the results, further experimental directions can be determined, mainly considering a larger number of specimens with different properties. These and other findings provide the basis for the ever-expanding field of research on load-bearing straw bales in construction.