Journal of the International Association for Shell and Spatial Structure Vol. 60 No. 3, 2019. Access >>
M. Seixas; L.E. Moreira; J. Bina; J.L.M. Ripper
Abstract: Ultralight bamboo structures with flexible joints comprise a novel construction system that can meet the global demand for sustainable buildings, such as multi-use pavilions and temporary structures for disaster relief and humanitarian purposes. In this work, modular self-supporting space frames were designed, fabricated, and experimentally analyzed using bamboo culms, textile ropes, and biocomposite rings. Numerical models and a 1:3 scale prototype were used to investigate the structural response under sustained loadings. The mean values of 5.4 GPa for Young's modulus (E), a specific gravity (G) of 8 kN/m³ , and a Poisson's coefficient (ν) of 0.3 were adopted for the bamboo members. The prototype, constructed with two modular space frames, was tested under both symmetric and asymmetric loading conditions during 43-day static tests. A pronounced nonlinear behavior was observed for the symmetric loading of 4.8 kN and the asymmetric loading of 3.5 kN, whereas failure occurred at a total load of 6.5 kN for the asymmetric configuration, 7.5 times the prototype's self-weight. The observed failure of bamboo members was governed by crushing under bending, followed by local buckling of the upper rafters below the load application points. The experimental results were compared with numerical models to determine an effective modeling strategy for reproducing the actual structural behavior. A comparison revealed that the eccentricity of members at the joints must be considered for a reliable prediction and that creep can be accounted for through appropriate reductions in the modulus of elasticity. The observed differences are attributed to the sliding of members at joints under higher loads and due to local second-order effects. The presented study investigates a mobile bamboo roof structure with flexible connections. The developed ultralight structural system built with modular space frames, tensile pantographic grids, textile joints in polyester ropes and biocomposites, is capable of supporting itself. Prefabricated hinged flexible connections (HFC), designed for the structure, allow for a deployable mechanism, free of torsional stresses in the bamboo bars. Nonlinear analysis using the finite element method (FEM) was used to determine the forces in the structure. Static loading patterns for wind loads were investigated and it was determined that the applied forces can be safely resisted by the structural members. A numerical model, physical models and full-scale prototypes were used to investigate the complex mechanical behavior of the bamboo structure. Selected design guidelines are also introduced.
