International Journal of Space Structures, Vol. 36 (2) 137-151, 2021, Access >>
M. Seixas; L.E. Moreira; P. Stoffel; J. Bina; J.L.M. Ripper; J.L. Ferreira; K. Ghavami
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. Self-supporting bamboo structures are ultralight architectural modules applying bamboo round poles, tensile pantographic grids and textile membranes. The structural system applies articulated flexible joints in polyester ropes and locking biocomposite bandage rings, keeping bamboo bars free of torsion stresses. An experimental 1:3 scale prototype and a full-scale structure were fabricated to make previsions about the physical and mechanical behavior of the structure. The experimental results were verified applying a numerical model for the structure. In turn, the flexible joints were analyzed theoretically. The computer model was analyzed using the finite element SAP2000 program. The numerical results were in close agreement with the experimental results specifically for the structural behavior of the flexible joints.
