Towards a Design Method for Bamboo Geodesic Domes

Abstract

This Master of Science thesis depicts the research done on geodesic dome structures and tensile bolted bamboo connections. The report includes a parametric structural analysis of bamboo geodesic domes assessing the influence of openings, local and global stability, geometrical non-linearity, and the maximum possible dome diameters for domes constructed with Guadua angustifolia and Phyllostachys pubescens. The considered load cases are selfweight and a point load on top of the dome; the latter includes the option of incremental load application and geometrically non-linear analysis. Rules of thumb are derived indicating boundary conditions under which global buckling of half-spherical icosahedron-based geodesic domes does not occur. Furthermore, a comparison of geodesic domes and half-spherical shells is conducted with respect to stability. One of the main challenges in bamboo structures is the design of tensile connectors that exploit bamboo’s tensile strength, avoid splitting, and provide a predictable, ductile failure. In the context of the design and strength prediction of a bolted axial bamboo connector, experiments assessing the dynamic Modulus of Elasticity and compression strength of Guadua angustifolia and Phyllostachys pubescens were conducted. For both properties a significant correlation with density was found. Additionally, the behaviour of bolted connections was simulated by testing the bolt bearing and splitting strength of Phyllostachys pubescens in a single bolt test with square and round bolts. It was found that square bolts result in ductile embedment failure with large displacements. Special focus was paid to the influence of nodes on strength and stiffness; a 3D scan and electron microscopy of the nodes of Guadua angustifolia and Phyllostachys pubescens were made. Findings from microscopic investigation matched findings from experimental testing: Nodes had a positive influence on embedment and splitting strength and an overall negative effect on full-culm compression strength and compressive Modulus of Elasticity. Last but not least, the insights gained in this research were combined in a case study of a bamboo geodesic dome with elliptical door opening. The case study adopts a probabilistic safety concept and partial safety factors in the style of the Eurocodes.