Interactive Effects of Node, Location and Loading Orientation on the Flexural Properties of Ethiopian Highland Bamboo ( Oldeania alpina (K. Schum.) Stapleton)

The flexural behavior of 180 split bamboo samples was examined in this study, along with the impacts of loading orientation, culm location and node presence on Ol deania alpina flexural properties. The material’s anisotropic, functionally graded anatomy was confirmed by the results, which showed significant main effects of node presence and loading orientation on flexural stiffness ( MOE f ) and strength (MOR) (p < 0.001). Nodes improved both properties ( MOE f 62%; MOR 49%), establishing it as the primary contribution, while outer compression produced superior performance ( MOE f 26%; MOR 18%). The top sections deformed 37% more than the bottom sections due to a significant thickness gradient, and position significantly influenced the MOE f (p = 0.024), with the middle culm sections exhibiting the highest values. Crucially, the outer compression mode significantly increased the node's stiffening impact, with flexural stiffness and strength reaching values as high as 18.29 GPa and 234.26 MPa, according to a significant Node × Loading Orientation interaction. This, together with a Node × Location interaction, suggested that the node's ability to reinforce changes across the culm. The load-deflection curves and flexural stress-strain behaviour were explained by the hierarchical structure of bamboo. According to the study’s findings, Oldeania alpina is a hierarchically optimized natural composite whose remarkable performance results from the coordinated use of longitudinal direction, loading orientation and nodal architecture. These findings offer recommendations for the high-performance use of this bamboo in structural design.