Buckling behaviour of cold-formed steel beam C-lipped sections using Bambusa spinosa Roxb. (Thorny Bamboo) strips as stiffening elements

This study uses a series of four-point bending tests to investigate the structural performance of cold-formed steel beam sections, both with and without bamboo stiffeners. The cold-formed steel beam sections without stiffeners (Specimens 7, 8 and 9) demonstrated maximum moments of 0.274 kN·m, 0.216 kN·m and 0.462 kN·m, with corresponding midspan deflections of 8.6 mm, 1 mm and 22 mm, respectively. In contrast, cold-formed steel C-lipped beam sections with 10 mm bamboo stiffeners (Specimens 1, 2 and 3) exhibited significantly higher maximum moments of 1.28 kN·m, 1.50 kN·m and 0.76 kN·m, with deflections of 1.8 mm, 10 mm and 20 mm. Beam sections with 5 mm bamboo stiffeners (Specimens 4, 5 and 6) showed maximum moments of 0.79 kN·m, 1.20 kN·m and 0.77 kN·m, with deflections of 2.9 mm, 11.15 mm and 9.3 mm. Bamboo stiffeners, particularly those 10 mm thick, substantially improved the structural performance by increasing the load-bearing capacity and reducing deflection. The study also investigated the buckling failure modes, identifying local, flexural and flexural torsional buckling behaviours that varied with the thickness of the bamboo stiffener. The results confirm the effectiveness and sustainability of bamboo stiffeners in enhancing the structural stability of cold-formed steel sections despite potential issues related to material inconsistencies and long-term performance. • Improved Structural Performance with Bamboo Stiffeners: Cold-formed steel beam sections with bamboo stiffeners, especially 10 mm thick ones, demonstrated significantly higher maximum moments and reduced deflections compared to unstiffened sections, showcasing their effectiveness in enhancing load-bearing capacity. • Failure Modes Identified: The study observed local, flexural, and flexural-torsional buckling failure modes, with variations influenced by the thickness of the bamboo stiffeners, providing insights into the structural behavior under four-point bending tests. • Sustainability and Challenges: Bamboo stiffeners not only improved structural stability but also highlighted their potential as a sustainable material choice. However, challenges related to material inconsistencies and long-term performance warrant further investigation.