Compressive behavior of concrete-filled multi-cavity composite rectangular columns

Concrete-filled multi-cavity pultruded composite rectangular column are proposed to improve the mechanical performance of rectangular pultruded profiles and their confinement effectiveness on the concrete core. The axial compression tests were carried out on the concrete-filled multi-cavity composite rectangular columns and related multi-cavity pultruded tubes. The effects of applications of the multi-cavity structure and lattice-webs on the failure modes, bearing capacity and ductility of specimens were investigated. The results reveal that the multi-cavity structure effectively improves the brittle manner of pultruded tubes, and thus improves the mechanical performance and the confinement efficiency of pultruded profiles, with an average 53.08% increase in the peak load and an average 27.45% increase in the axial stress of confining concrete. Moreover, applications of lattice-webs have positive effects on improving the interface bonding performance and thus better deformation capacity of the structure is observed. The average ductility coefficient of concrete-filled specimens reinforced with lattice-webs is 2.23, higher than that of specimens without lattice-webs (1.88). Applications of lattice-webs further improve the confinement effectiveness of the multi-cavity structure on the concrete, thus increasing the peak load of specimens. The maximum increase in the peak load of the concrete-filled multi-cavity structure is 21.17%, which is much higher than 7.44% of specimens without lattice-webs. A simple design-oriented model was proposed to predict the peak load of concrete-filled multi-cavity specimens and related multi-cavity pultruded tubes. The results are consistent with the test data.