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: The creep behavior of bamboo culms under long-term loadings was investigated in the present work. Phyllostachys aurea bamboo samples were subjected to four-point flexural creep tests at loads corresponding to 30%, 50%, and 80% of the bamboo's short-term bending strength. Creep and recovery behavior were evaluated for each loading level at room temperature over 398 days, allowing the attainment of primary, secondary, and tertiary creep stages. The failure of one creep test sample occurred at 73 MPa, and the failure mode due to creep was described. Creep mechanisms assessed included node flexibility, cylindrical bending, and shear. Node flexibility contributed 50–74% of total deflection, cylindrical bending contributed 24–48%, while shear contributed less than 2%. A four-element Burgers mechanical model was proposed, matching the experimental results for all loading levels. A viscous coefficient parameter of 4.3 to 30× 103 GPa.day was inferred, corresponding to the linear dashpot n1. These models estimated the bamboo culm deflection over time and predicted failure at a 40% increase in deflection. Overall, this study provided comprehensive insights into the long-term structural behavior of bamboo culms for use in design and engineering applications. 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.
