Experimental study on the hysteretic behavior of ECC-encased CFST columns

Concrete-encased concrete-filled steel tube (concrete-encased CFST) columns, which is a conjunction of normal steel reinforced concrete (RC) and CFST columns, have been widely used in structural engineering. However, the outer RC component tends to crush in the early stage due to the significantly different mechanical performance of outer concrete and inner CFST. In this paper, it is proposed to substitute outer concrete with engineered cementitious composite (ECC) to form ECC-encased CFST columns. This paper presents an experimental study on the hysteretic behavior of ECC-encased CFST columns. Eleven specimens, including seven ECC-encased CFST columns and four concrete-encased CFST columns were tested under cyclic loading. According to the test results, ECC-encased CFST columns exhibited stable ductile behavior and the cumulative energy dissipation is about twice as much as that of concrete-encased CFST columns with same geometry. Also, the increase of steel tube diameter and stirrup ratio have positive effects on the hysteretic behavior of ECC- encased CFST columns.