Journal of the International Association for Shell and Spatial Structure Vol. 65 No. 2, 2024. Access >>
M. Seixas; L.E. Moreira; D. Cardoso
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. 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.
