Journal of the International Association for Shell and Spatial Structure Vol. 65 No. 2, 2024. Access >>
M. Seixas; L.E. Moreira; D. Cardoso
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. Joints are one of the main problems concerning the design of bamboo structures. This paper proposes a classification of the main joints applied in full-culm bamboo structures according to their constructive behavior, subdivided into semi-rigid and flexible joints. A novel flexible joint called the Hinged Flexible Connection (HFC) for lightweight bamboo structures is developed and analytically described, allowing for a deployable motion in the center of the joint and mobile assembly procedures. The joining system utilizes lashed polyester ropes and bio-composite rings coupled in the bamboo culms working as geometric and mechanical constraints. The HFC has the potential to substitute bolted joints for the engineering design of bamboo structures.
