Axial Compressive Behavior and Estimation Method of Bearing Capacity of Precast Reinforced ECC Shell–Concrete Column

Engineered cementitious composite (ECC) is a material with high-ductility and damage-resistance capacity, which can mitigate cracking, prevent cover spalling caused by concrete brittleness, and inhibit reinforcement buckling. However, the difficulty of on-site casting and the relatively high cost of ECC limit its application. On this basis, this study proposed an innovative fully precast reinforced ECC shell–concrete (PREC) composite column and investigated its axial compressive behavior. Static axial compression experimental, theoretical, and numerical studies were performed on the PREC composite columns and compared with a cast-in-place (CIP) conventional concrete (CC) column and a CIP ECC column. The experimental results demonstrated that the incorporation of a precast ECC shell markedly enhanced the ultimate bearing capacity, ductility, and energy absorption capacity of the CC column. Notably, under an optimized shell thickness, PREC composite columns even exhibited slightly higher ductility than CIP ECC columns. The proposed theoretical model, which accounted for the combined confinement effects of the stirrups and ECC shell, can be used to evaluate the ultimate bearing capacity of the PREC composite columns. Furthermore, the validity of the proposed model was verified through numerical simulations. The parametric analysis of size effects demonstrated that the proposed bearing capacity method effectively accounts for the influence of specimen size.