Large torsion on elastic lamella grid structures

Elastically curved grid structures pose great potential to simplify fabrication as the structure may consist of straight elements [1]. However, for assembly, erection and load bearing the structures restraint forces need to be considered. While bending stresses are well explored, nonlinear normal stresses due to torsion (helix-strain) are often neglected. For large twists of lamella profiles in a practical scale, the helix-strain effects need to be considered as they amount significantly to the lamellas torsional stiffness and utilization. For lamella profiles, calculations according to Lumpe and Gensichen [2] can be simplified. The “Inverse”-method allows simulations using the final shape as initial simulation geometry and therefore reduces the complexity of static calculations. This paper presents a method to consider helix-strain effects for the simulation of lamella grids using the IGA “Inverse”-method. This method has been applied to simulate the behavior of a grid structure as central element of a canopy. A simplified simulation offered valuable information about the flat state at assembly and necessary forces to erect the grid structure.