Axial compressive creep behaviour of a square steel tube/bamboo plywood composite column with binding bars

Four specimens of a thin-walled square steel tube/bamboo plywood composite hollow column with binding bars (SBCCB) were each subjected to an axial compressive creep test and a subsequent axial compression test to examine their axial compressive creep behavior and post-creep compressive failure modes as well as to analyze the effects of long-term loading on the ultimate axial compression-bearing capacity of the SBCCB. The results show that the axial compressive creep strain decreased with increasing slenderness ratio and increased with increasing axial compressive stress. The creep–time curves of the specimens with various slenderness ratios all exhibited a transient creep stage and a steady-stage stage. Temperature and humidity variations affected local creep behavior. Creep significantly affected the axial compression-bearing capacity as well as the axial and lateral deformability of the SBCCB. The rheological mechanics-based Burgers model can well predict the creep strain development of the SBCCB.

Axial compression testing of bamboo plywood-encased thin-walled steel tube/stone dust concrete columns

A novel structural member, the bamboo plywood-encased thin-walled steel tube/stone dust concrete composite column (BSDCC), was investigated in this study. Axial compression tests were conducted on 10 BSDCC specimens; their failure characteristics and modes were examined, and the effects of the stone-dust concrete content ratio and strength, specimen slenderness ratio, cross-sectional composition and binding bar confinement pattern, and binding bar spacing ratio on the bearing capacity and deformation of the columns were investigated. Two main compressive failure modes were observed: (1) adhesive failure by cracking and debonding between the bamboo plywood boards and between the bamboo plywood and the steel tube and (2) compressive-flexural failure of the bamboo plywood between the binding bars in the middle of the specimen. For specimens with the same cross-sectional dimensions, the cross-sectional content ratio of the stone dust concrete impacted the deformation and failure mode but did not significantly affect the ultimate bearing capacity. The bearing capacity decreased with increasing specimen slenderness and binding bar spacing ratio and increased with increasing stone dust concrete strength and bamboo plywood constraint (in terms of the cross-sectional composition and binding bar restraint pattern). A model for the ultimate bearing capacity of BSDCCs was established through regression analysis.