Development of analytical model for predicting compressive behavior of engineered cementitious composites-concrete encased steel composite columns

Analytical models which can reliably predict the load-deformation behaviors and the ultimate strength of columns are indispensable tools for the practical design. In this paper, an analytical model is developed to predict the compressive load-deformation behavior and the ultimate capacity of engineered cementitious composite confined concrete encased steel (ECC-CES) composite columns. The proposed analytical model employs the effective material stress and strain compatibility approaches for the predictions of compressive load- deformation response of ECC-CES columns. The material constitutive models for ECC, concrete, and steel are first established, and then used in the analytical model. The effect of ECC and steel confinement on the concrete core and the softening behavior of steel column due to compression buckling are also considered. Based on the experimental results, appropriate strength reduction factors are proposed so that the effective material stresses can be calculated. The strength predictions from the proposed analytical methods and different design codes are compared with the experimental and numerical results. It was found that the proposed analytical models using effective material stresses gave better predictions than many commonly used design codes.