Assessment of the load-bearing capacity of textile-reinforced shell structures created with a free form-finding approach

Shell structures are primarily subjected to compressive stresses if their geometry is adjusted to the applied loading. Still, the geometry in a real environment usually deviates from an optimal form for load-bearing due to tolerances and architectural demands, thus causing additional bending moments (m) and normal forces (n). The use of textile-reinforced concrete (TRC) makes it possible to reduce thickness and thus the dead weight of a shell, though it also increases the sensitivity for deviations from perfect conditions. Additionally, textile reinforcement typically consists of two orthogonally aligned reinforcement layers of yarns, while the principal stress directions relevant to the shell design typically diverge from the yarn orientation. Hence, the cross-section suffers a reduced resistance due to the anisotropic material properties of the textile reinforcement. In this paper, we investigate the load-bearing capacity of existing TRC-shell structures that were created with a free form-finding approach. Given the anisotropy of the textile reinforcement, the analysis of the shell must not only consider the n-m interaction but also the principal stress direction for each specific location and load situation within the structure. This is considered by the verification concept presented here, which follows the semi-probabilistic design format from the European Codes. It could be shown that this new methodology for assessing free form shells can be used identify the most critical parts of such shells.