Axial compressive behaviors of engineered cementitious composites-encased concrete filled steel tube columns after fire exposure

Abstract

Engineered cementitious composite (ECC)-encased concrete filled steel tube (CFST) column, which is composed of outer steel reinforced ECC and inner CFST components, has broad application prospects in high-rise buildings due to its higher strength and ductility than the concrete-encased CFST column counterpart. This paper investigates the fire performance of ECC-encased CFST columns under and after fire exposures. Totally thirteen ECC-encased CFST columns and two concrete-encased CFST columns were prepared and tested considering different parameters, i.e., heating-up time, stirrup spacing and fire sides. It was found that the outer ECC component provides better fire protection to the inner CFST than the conventional concrete. Besides, the axial compressive strength and ductility of the ECC-encased CFST column were 32.2 % and 10.3 % higher than those of concrete-encased CFST columns after fire exposure. A finite element (FE) model and design equations were also proposed and verified by the experimental results, which could be applied to simulate and predict the compressive behavior of ECC-encased CFST columns after fire exposure.