Flexural creep behaviors of bamboo subjected to different gradient variation directions and relative humidity

Abstract

As more and more bamboo materials have been used for buildings, the bamboo creep property deserves more explorations because it is important to structural design and plays a critical role in serviceability of structure. In this study, the creep mechanism of bamboo over a wide range of scales from microstructure and bending flexural property to creep behavior were investigated. Firstly, the gradient functions of different vascular bundle distribution directions were obtained. The average value of gradient index n was respectively 2.16 and 0.29 when x axis ranged from different directions. Secondly, the flexural property test under different loading directions were analyzed. There were two groups, one group (OT) was the fiber-rich outer culm wall in tension side, the other group (Oc) was the fiber-rich outer culm wall in compression side. It was concluded that Group OT showed larger MOR and smaller MOE than Group OC. In addition, the total energy consumed of Group OT was larger than Group OC, while the elastic energy was smaller. Thirdly, the creep property under different loading directions and humidity were examined, which is unique because no research about the bamboo creep performance under different humidity conditions has been completed according to the literature review. The creep deflection of Group OT was larger than Group OC whatever constant humidity or variable humidity was used. The relative creep of Group OT was smaller than Group OC under high humidity (90% RH) and variable humidity (30% RH-90% RH-30% RH), while larger under low humidity (30% RH). Compared to bamboo-based products, the stress level was more sensitive on the creep property of bamboo, and the anti-creep property of bamboo was lower than bamboo-based products.