Flexural response of bamboo-epoxy frames

Bamboo is a highly sustainable and renewable material and is popular in housing in developing countries though this is restricted to at most two storey dwellings. Indeed although many species of bamboo are known to have... [ view full abstract ]

Bamboo is a highly sustainable and renewable material and is popular in housing in developing countries though this is restricted to at most two storey dwellings. Indeed although many species of bamboo are known to have suitable tensile and compressive strengths for structural use, its high variability, low stiffness and joint connections create real engineering design challenges which mitigate against its use in medium density housing, which is currently a restriction on its use in heavily populated cities in practice. To overcome these deficiencies, a series of full scale bamboo-epoxy Portal frames have been manufactured in India and tested in Ireland, comprising a mixed bundle of small diameter Dendrocalamus Strictus bamboo bound by an epoxy-fibre composite glue. The bundle averages out much of the variability in the beams/columns, providing considerable load carrying capacity and enhanced stiffness due to composite action. The corner joints are formed by embedding mild steel bars in the individual beam/column cylindrical hollow sections, bound together with a novel epoxy/sand composite, yielding an integral rigid connection between the beams and columns. When a lateral and/or vertical load is applied, influencing its load capacity, the flexibility laterally introduces considerable secondary moments in the columns which cause delamination of the epoxy in shear without failure of the bamboo. The presence of 60 strain gauges throughout each frame enables stress reversal and load transfer to be clearly observed prior to and during the flexural response. The bending moment diagrams and collapse mechanisms confirm the causes of this non-linear behaviour. The resilience of the frame during the plastic phase is such that considerable recovery is noted to occur on unloading. The complex behaviour of this frame is described in full in this paper leading to a good understanding as to how such a composite might help have the potential to alleviate the housing problems in those parts of the world which have abundant indigenous bamboo.