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Title: Stress-Strain Model of High-Strength Concrete Infilled in Steel Tube

Author(s): Nengpan Ju, Hua Zhao, Rui Han, Zhihua Liu, and Chang Yang

Publication: Structural Journal

Volume: 119

Issue: 6

Appears on pages(s): 193-203

Keywords: concrete-infilled circular steel tube (CFCT) stub columns; constitutive model; high-strength concrete; load-carrying capacity; local buckling

DOI: 10.14359/51734804

Date: 11/1/2022

To evaluate the load-carrying capacity of structures even after strength degradation at large deformations, a stress-strain model of high-strength concrete-infilled circular steel tube (CFCT) stub columns under uniaxial compression is proposed. Results of 44 CFCT tested stub columns in previous research were collected to calibrate the accuracy of the proposed model. The nominal compressive curves of the concrete core were obtained by subtracting the theoretical constitutive curves of circular steel tubes from the corresponding experimental curves of CFCT stub columns. The confining stress of this model is determined by using the Mohr-Coulomb strength theory to analyze the experimental database. This model takes account of the effect of local buckling of steel plates on confined high-strength concrete, which is implicit in the existing model of confined concrete. The model consists of two parts: one is a curve with ascending and descending branches, which is based on the confined concrete model proposed by Sakino and Sun; the other is a horizontal line after the axial shortening strain exceeding 0.02. Verification by experimental load-deformation curves of the CFCT indicated that the proposed model in conjunction with the theoretical model of circular steel tubes previously published by authors can well predict the complete compressive behavior of CFCT stub columns. In addition, equations to predict the ultimate load carrying capacity and corresponding strain of the CFCT stub columns with infilled high-strength concrete are proposed, which are verified reliably with high accuracy even for the ultra-high strength concrete beyond the application range of existing codes.