Bamboo structural member behavior : culm flexure and bolted connections

Abstract

Bamboo has been increasingly popular as a structural material in recent decades, because of its cost-efficiency, high strength-to-weight ratio, and sustainability. However, currently there is incomplete understanding on bamboo structural member behavior. This study initially describes analytically bamboo culm flexure, in terms of failure load and stiffness loss quantification. It concludes that critical failure mechanisms are tension perpendicular to the fibers (with potential tension-shear interaction), and longitudinal compression. Main cause for stiffness loss of bamboo culms in bending is longitudinal splitting, with secondary cause being non-linear geometric effects at the large deflection stage. In the case of a single crack at the culm side in particular, main cause of the stiffness loss are torsion-induced deflections, with secondary cause being shear deformations. Further, shifting the focus to bolted bamboo connections, the study initially characterizes the bolt embedment phenomenon under the prism of dimensional analysis. When described in dimensionless terms (i.e., normalized with bolt diameter and density) the average embedment properties become a function of a single dimensionless product (the ratio of culm thickness to bolt diameter) and considerable order emerges. The average dimensionless embedment properties follow “universal”, species-independent curves. Subsequently, the study establishes a modified foundation modeling approach to macroscopically capture the embedment phenomena in bolted bamboo connection numerical simulations. The proposed approach assumes that foundation zone material properties are the nominal embedment properties, and rationally defines the dimensions of the foundation zone. Finally, employing verified bolted connection models in a parametric analysis, the study concludes that larger bolt clearance and distance between the culms yield lower connection strength and stiffness, that numerical models adopting minimum (as opposed to average) culm dimensions yield more realistic results, and, lastly, that, when increasing the bolt diameter, bolt embedment displacement is more critical for total connection displacement than bolt deflection.

Date of Award	2022
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Ilias DIMITRAKOPOULOS (Supervisor)