The structural geometry of a beam element from 4 torqued strips

When assembling a tube from 4 identical, thin-walled, flexible, rectangular strips, which are hinge-joined along their longitudinal edges, a hollow, square cross-section is generated. One option for restraining the tube’s 1-DOF-mechanism around its longitudinal axis is to cross-wisely connect its ends at a common seamline. This procedure causes a twist of 90° and sideward shifts of each of the four strips. We provide a description and comparison of the structural geometry of such beam elements. Our investigations are based on physical prototypes, photogrammetric reconstruction, and computational simulations. The beam’s geometrical stiffness, paralleled with its ease of fabrication and assembly opens new avenues for the design of lightweight structures, firstly used in the realization of the kinematic Zero Gravity pavilion at Aalto University.Peer reviewe