Steel beams strengthened with novel bamboo scrimber stiffeners: Experimental investigation and mechanical behaviour

I-shaped steel is prone to instability failure when used as beams. To address this issue, a novel approach for reinforcing steel beams with bamboo scrimber (BS) was introduced. Using bamboo scrimber as stiffeners reduces steel consumption by replacing the commonly used welded steel plate stiffeners, while also preventing internal structural defects caused by welding. The bamboo scrimber stiffeners (BSSs) were bonded to both sides of the steel web with epoxy structural adhesive to provide anti-buckling support. Bending tests were conducted on two pure I-shaped steel beams (CG) used as control beams, along with 10 I-beams strengthened with novel BSSs (JQL-0/1/2/3/4) of the same span, with BSSs at varying spacings (700 mm, 350 mm, 233 mm, 175 mm, and 140 mm) as a variable, and two specimens in each variable group. The findings indicated that the failure modes of the novel beams include two types: debonding failure of BSSs and lateral-torsional buckling (LTB). Compared to pure I-beams, the I-beams strengthened with BSSs showed significantly greater improvements in resisting LTB failure and enhancing ductility than in increasing load-carrying capacity. As the BSSs increased, the critical ultimate load of the I-beam strengthened with BSSs gradually increases from 6.20 % to 12.31 % over the CG specimen. Comparing with the pure I-beam, the reinforcement spacings (a) of JQL-0, JQL-1 and JQL-2 are 700 mm, 350 mm and 233 mm, and the ductility is increased by 47.27 %, 104.61 % and 145.18 %. When the a is reduced to 175 mm and 140 mm, the ductility coefficient increases by 149.50 % and 150.31 %, respectively. In addition, the ductility coefficient (µ_∆) of I-beams strengthened with novel BSSs was analyzed and predicted to support practical applications of BSSs in engineering. The regression prediction of µ_∆ has a goodness of fit (R²) of 0.9753 and an RMSE (root mean square error) of 0.3287.