Journal of the International Association for Shell and Spatial Structure Vol. 57 No. 3, 2016. Access >>
M.A. Seixas; J.L.M. Ripper; 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. This article presents a new typology to build deployable pavilions based on a mobile self-stabilizing bamboo structure. The architecture is characterized by lightweight space trusses of treated bamboo poles covered with a bio-composite made of cotton fabrics, clay, PVA glue and castor oil polymer. The connections of the deployable structure were developed using textile moorings, that minimized efforts on the assembly of the structural members. The roof consists of bamboo pantograph gridshells covered by tensioned PVC canvas. The assembling procedure employs prefabricated structural modules prepared on the floor of the building site and then lifted manually by a set of projected elevators. The method presents a simplified mounting and dismantling process of the structure. The proposed bamboo structure presents an easy adaptability without the need of a specific construction site for its assembly and needs only a mounting area. The mobility of the pavilion, the manufacturing techniques and the natural materials favored the design of new forms for construction, with clean use of local spaces. These considerations resulted in an agile execution with minimum waste, in addition to low energy consumption and low environmental impact for the production of the structure.
