Axial compressive behaviour of precast steel reinforced ECC shell-concrete composite column

To economically, effectively and reasonably apply engineered cementitious composites (ECC) on improving the mechanical properties of reinforced concrete (RC) column, a novel composite column consisting of precast concrete core and precast steel reinforced ECC shell (SECC-PC composite column) was developed in this paper. SECC-PC composite column specimens as well as the contrast pure RC column and pure ECC column specimens were designed and manufactured. The axial compression tests were conducted to investigate the axial compression behaviours of the specimens. And the influence law of ECC shell thickness and stirrup spacing on the axial compression behaviours of the specimens was systematically analyzed. Based on this, the calculation equation of axial compressive bearing capacity of the composite columns considering the additional confinement effect of the stirrup and ECC shell was established. The results show that, compared with the RC column, the SECC-PC composite columns and ECC column exhibit obvious ductile failure characteristic, and no ECC spalling and no segregation phenomena between the precast ECC shell and concrete core occur at failure state. With the ECC shell thickness increasing, the peak load and displacement of the precast composite columns increase, while the relevant initial stiffness and ductility coefficient decrease. The incorporation of the precast ECC shell can significantly improve the ductility and energy dissipation capacity of the specimens. Within the designed ECC shell thickness in this study, the ductility coefficients and the accumulated energy dissipation of the precast composite columns are 1.13-1.35 times and 2.13-2.46 times larger than that of the RC column. With the stirrup spacing decreasing, the bearing capacity improves, while the post-peak ductility and energy dissipation capacity of the specimens improve remarkably. The axial compressive bearing capacity of the composite column should take the constraint effect of the prefabricated ECC shell into account. The relevant bearing capacity calculation equation can be used to calculate the axial compressive bearing capacity of the composite column.