Predictive structural grading of Ethiopian highland bamboo (Oldeania alpina (K.Schum.) Stapleton) culms using regression analyses of compression properties

We determined the major predictor of the compressive load capacity of Oldeania alpina . This may enable the use of intact whole culms in the construction sector, given the increasing popularity of bamboo in structural applications. An extensive experimental investigation of compressive properties was conducted in two independent laboratories (AASTU and AAiT). Data normality tests were carried out prior to the datasets being pooled for a comprehensive analysis, and then regression analyses were used to identify the optimal physical properties. Additionally, the effects of culm height location and node presence on compressive and physical properties were evaluated. Linear mass, wall thickness, diameter, moisture content and density had the strongest relationships with compressive performance. While density predicted compressive strength inefficiently, linear mass performed best in simple regression (R² = 0.553 for ultimate load), and multiple linear regression significantly improved predictive accuracy. The position of the culm had a greater impact on mechanical properties (ultimate load, strength, stiffness) than the existence of a node. Nodes did not lower the culm's ultimate load capacity (p = 0.507). Despite having a lower compressive strength, bottom portions demonstrated a significantly higher ultimate load due to their bigger cross-sectional area. The exceptional mechanical potential of Oldeania alpina was confirmed by its mean compressive strength of 62.79 MPa, which makes it ideal for contemporary load-bearing structures. 95% confidence bands were used to develop strength and load-capacity grading systems, and we found that capacity-based grading, which uses linear mass, was more reliable and trustworthy for commercial grading. • Ethiopia is the country in the African Continent with the largest area of natural bamboo culms. • Regression-based grading, emphasizing linear mass and capacity metrics, effectively predicts Ethiopian highland bamboo performance under compression. • Oldeania alpina is a high-performance structural bamboo species with mean density of 813 kg/m³, compressive strength of 63 MPa, and MOE of 21.5 GPa, values that surpass most commercial timber species and many tropical bamboos.