Abstract:
In order to study the feasibility of replacing steel tubes of concrete filled carbon fiber-reinforced polymer (CFRP)-steel tube columns with ultra high performance concrete (UHPC) tubes, a novel concrete-filled CFRP-UHPC tube (CFFUT) column was proposed. The CFFUT column consists of a combination of UHPC precast tubes externally wrapped with CFRP and an internal cast-in-place filled normal concrete. Ten CFFUT columns, including two contrast columns, were tested under monotonic axial compression, and the influences of UHPC tube thickness, CFRP layer numbers and filled concrete strength were investigated. The results show that CFRP-UHPC tube can effectively improve the bearing capacity, deformation capacity and ductility of composite columns. The failure of CFFUT column is mainly manifested as the collapse of filled concrete, cracking of UHPC tube and rupture of CFRP. The integrity of CFFUT column is good after failure, and it belongs to ductility failure mode. The ultimate bearing capacity of CFFUT column is positively correlated with the thickness of UHPC tube, the number of CFRP layers and the strength of filled concrete. Ductility factor increases with the increase of UHPC tube thickness and CFRP layer number, and increases first and then decreases with the increase of filled concrete strength. The interface strengthening mechanism of CFFUT column is revealed. The ultimate bearing capacity of CFFUT columns is 93.9%-203.5% higher than that of normal concrete columns with the same section, and the ultimate bearing capacity of CFFUT columns is equivalent to that of concrete-filled CFRP- steel tube columns to a certain extent. The theoretical calculation model of ultimate bearing capacity is established and verified by finite element analysis. The calculated and simulated values are in good agreement with the test results.