Creep behaviour of bamboo

The phenomenon of creep, particularly in anisotropic and fibre-reinforced materials, is critical to structural design. The objective of this study is to study the creep behaviour of bamboo in particular considering the effect of specimen orientation. The experiment is motivated by the restriction of sustained load on various materials, particularly fibre reinforced materials, due to creep. In this study, half of the radially-cut Bambusa stenostachya (Tre Gai) specimens subjected to a sustained load were oriented so that the fibre-rich outer culm wall is in tension; the other half were loaded so that the outer culm wall is in compression. All tests were conducted in accordance with, and assessed based on, established creep test standards for wood. The orientation of the specimen was found to have significant effect on both the creep behaviour and residual strength of creep-conditioned specimens. The results showed that the bamboo loaded with the outer culm-wall in tension (OT) exhibited (a) a larger modulus of rupture; (b) a lower apparent modulus of elasticity; and (c) a lower residual strength when compared to specimens with their outer culm-wall in compression (OC). In terms of post-creep residual strength, creep conditioning appeared to have a strengthening effect on OC specimens and a detrimental on OT specimens. Results were assessed against common design values for timber and it concluded that the Tre Gai bamboo is seemingly better able to withstand higher sustained loads than timber.