Mechanical properties of large-scale parallel bamboo strand lumber under local compression

Abstract

Large-scale parallel bamboo strand lumber (PBSL) structural elements are often subjected to local compression especially in beam-to-column connections as well as in beam-to-beam connections. The current paper presents an experimental investigation on the local compression behaviour of PBSL. 20 specimens were collected from different parts of a PBSL block under radial and tangential compression loading. Load-displacement curves of all specimens were recorded and observed failure patterns were carefully investigated to understand underlying mechanics. Tangentially loaded specimens predominantly failed due to debonding of fibres triggered by deformations perpendicular to the grain. On the other hand, radially loaded specimens showed a combined failure caused by debonding in perpendicular to the grain direction as well as tensile failure of bamboo fibres in the longitudinal direction. Key design parameters such as elastic modulus, stiffness, ultimate strength and Poisson's ratio for all specimens were computed and compared against end vs middle specimens as well as radial vs tangential specimens. Radially loaded specimens showed higher load carrying capacity due to better bonding, whilst the specimens collected from the middle part of the PBSL block were relatively more ductile than the others. Analytical models for load–displacement repose as well as for stress–strain behaviour were proposed for the considered specimens. Ramberg-Osgood based stress–strain model showed good agreement with test results.