Experimental study on eccentric compression performance of bamboo-encased timber composite columns

This paper presents an experimental investigation on the eccentric compression behavior of bamboo-encased timber composite (BETC) columns. A total of 54 specimens were tested under eccentric loading, considering experimental variables including slenderness ratio (i.e., 29.69, 39.59, 49.49), eccentricity (i.e., 20 mm, 40 mm, 60 mm), and loading direction (i.e., parallel and perpendicular to the lamination plane). The failure modes, load-axial displacement, load-lateral deformation, load-strain relationships, and lateral deformation distributions of the specimens were systematically analyzed. Results indicate that eccentricity and slenderness ratio significantly influence the failure mechanisms, transitioning from local crushing to global flexural buckling as these parameters increase. Loading direction markedly affects performance due to material orthotropy. Specifically, the specimens loaded parallel to the lamination plane exhibit higher ultimate loads, greater ductility, and more stable deformation compared to those loaded perpendicularly, where brittle transverse cracking and interface debonding dominate. Based on the test data, a simplified calculation method for eccentric compression capacity is proposed and validated. The average error of this method compared with the test results of all specimens was 6.67%. This study provides essential experimental evidence and design recommendations for BETC columns in practical engineering.