Study on axial compressive behavior of CFRP-constrained bamboo strips-circular thin-walled steel tube composite columns

To delay the failure of the adhesive, prevent premature buckling of thin-walled steel pipes, and to address the weaknesses of bamboo in fire prevention, insect prevention, and corrosion resistance, a novel type of composite columns, namely, CFRP-constrained bamboo strips-circular thin-walled steel tube columns was proposed. A series of axial compression tests were conducted on the composite columns (including nine short columns and four long columns)and the results were used to verify the finite element (FE) model. The verified FE model was then used to investigate the effects of thickness of bamboo strips, number of CFRP layers, steel pipe section and slenderness ratio on the axial compressive behavior of the columns. On this basis, the theoretical equations of the axial compressive capacity of the composite columns were proposed. The results show that there are three failure modes of the composite columns: the material damage in the middle of the columns, crushing failure at the end of the columns, and global instability failure. The bearing capacity of the composite columns increases with the thickness of the bamboo strips and the diameter of the steel pipes, and decreases with the slenderness ratio. CFRP has a significant confinement effect in the composite columns with small and medium slenderness ratios (λc≤50), but has a limited effect in the composite columns with large slenderness ratios (λc >50). When the slenderness ratio is less than 19, the composite columns would undergo material failure, otherwise the composite columns would fail by instability. The effects of various parameters on the improvement efficiency of the bearing capacity are different. The results of the test, finite element simulation, and theoretical analysis are in good agreement. The average error between the results by the theoretical equations and the experimental or finite element results is less than 5.0%, and the maximum error is less than 10%, indicating that the established calculation methods have high accuracy and are suitable for predicting the bearing capacity of CFRP-constrained bamboo strips-circular thin-walled steel tube composite columns. © 2022 Science Press. All rights reserved.