Comparative Structural Behaviour of Periodic Two-Layer Spatial Grids Inspired by Ammann A4 Geometry

This study investigates the structural behaviour of three periodic two-layer spatial grids inspired by Ammann A4 geometry. The proposed configurations combine tile-derived upper grids with lower subsystems formed by selected continuous Ammann lines, interconnected through diagonal members. These lines, which originally served as an auxiliary mathematical construction ensuring aperiodicity, are utilized here as the generator for a completely new concept of the grid’s bottom layer. Variants V1–V3 were compared with Ammann A4 and Unibat reference configurations using geometrically nonlinear finite element analysis under common loading, material, and member-section assumptions. Axial forces, resultant bending moments, and vertical displacements were evaluated across the configurations and their constituent subsystems. All lower-subsystem members in V1–V3 carried tensile axial forces. V1 exhibited the most uniform lower-subsystem force distribution, with a coefficient of variation of 4.0%, and the lowest peak axial-force magnitude and resultant bending moment among the proposed variants, at 324.68 kN and 72.57 kNm, respectively. V2 developed the highest corresponding peaks, at 448.32 kN and 129.12 kNm. V3 achieved the smallest maximum downward displacement among the proposed variants, at 18.60 cm, compared with 30.70 cm for V1 and 24.70 cm for V2. Unibat exhibited substantially smaller bending moments and displacements but required greater total member length and used a different support arrangement. The findings demonstrate that Ammann-line-based lower subsystems can develop continuous tensile paths, while revealing trade-offs between force uniformity, local demand, and deformation. The comparison characterises relative structural response rather than establishing code compliance or a universally preferable configuration.