Axial compressive behavior and model of laminated bamboo-filled high-strength steel tubular columns

Laminated bamboo is a sustainable low carbon material, but its brittle compressive response and susceptibility to longitudinal splitting limit its use in compression members. This study investigates the axial compressive behavior and modeling of laminated bamboo filled high strength steel tubular short columns. A total of 56 specimens, including circular BFHST columns, square BFHST columns, and unconfined laminated bamboo columns, were tested under monotonic axial compression. The effects of sectional shape, steel tube wall thickness, diameter or width-to-thickness ratio, and steel yield strength on failure mode, nominal axial stress-strain response, nominal ultimate axial stress, and ultimate axial strain were examined. The results show that steel tube confinement changed the response of laminated bamboo from unconfined compression to confined composite compression. Increasing the steel tube thickness from 4 mm to 6 mm increased the nominal ultimate axial stress and ultimate axial strain by up to 85% and 137%, respectively. Increasing the steel yield strength from Q460 to Q690 increased the nominal ultimate axial stress by 4–33%, while the ultimate axial strain increased only for the t4 specimens and decreased for the t5 and t6 specimens, with a maximum reduction of 31.7%. Circular specimens showed higher axial deformation capacity than square specimens because of more continuous lateral restraint. Based on the present tests and published data, a database of 93 steel-bamboo composite short columns was established, and models were developed for nominal ultimate axial stress, ultimate axial strain, and full range stress-strain response. The proposed models provide a basis for evaluating BFHST columns in sustainable structural applications.