Structural behavior of steel reinforced concrete composite columns with ECC permanent formwork: numerical simulation and parametric study

This paper investigates the eccentric compressive behavior and load-bearing mechanism of steel-reinforced concrete (SRC) composite columns with permanent ECC formwork (ECC-SRC) via numerical modelling. Nonlinear Finite Element Analysis (FEA) was firstly conducted to simulate the damage patterns and load-deformation response of ECC-SRC beam-columns and the experimental results tested by the authors are used to validate the FE model. Based on the verified FE model, an in-depth analysis was performed to unravel the load-bearing mechanism during the complete deformation response and explore the complex interaction behavior among each material component. After that, parametric study was carried out to evaluate the effect of material strength, ECC jacket thickness and the reinforcement ratio on the eccentric compressive behavior of ECC-SRC columns. Specifically, the potential interaction effect among each design parameter was discussed by extending the parameters to cover the normal range adopted in common practice. Finally, a simplified calculation method is proposed to predict the axial force-bending moment (N-M) curve of ECC-SRC columns with consideration of ECC tensile strength and material compatibility, and the design recommendations with regard to the matching grade of material strengths and the optimal ECC jacket thickness are also proposed to facilitate the design optimization.