Experimental investigation on the seismic performance of square concrete/ECC filled stiffened high-strength steel tubular columns

Abstract

Seismic action can lead to severe damage in the plastic hinge zone of concrete-filled steel tubular (CFST) columns, such as the localized buckling of the steel tubes and the crushing of the core concrete. Despite the numerous proposed cross-sectional configurations for CFST columns, the core concrete exhibits substantial damage under intense seismic action, making post-earthquake maintenance challenging. To mitigate the spalling of the core concrete under seismic action, this paper proposes the utilization of engineered cementitious composites (ECC), which is a cement-based composite material, for a certain height within the plastic hinge zone as a substitute for common concrete. Six square concrete/ECC-filled stiffened high-strength steel tubular (CFSHST) columns were fabricated and subjected to quasi-static tests. The effects of the yield strength of the steel tubes, cross-sectional configurations, and axial compression ratio on the seismic performance and failure modes of the CFSHST columns were investigated. Subsequently, a numerical analysis of these columns was conducted to discuss the effects of the compressive strength of the core concrete, the yield strength of the steel tubes, and the axial compression ratio on the seismic performance of the columns. Finally, a design formula for the load-bearing capacity of this type of column was established, and its accuracy was verified using experimental results and numerical model results. The results showed that the CFSHST columns with the ECC in the plastic hinge zone exhibited only minor cracks and no evident ECC spalling occurred. Moreover, the longitudinal steel bars were beneficial in alleviating the spalling issue of the core concrete in these columns. The proposed design formula for the load-bearing capacity can accurately predict the peak load of CFSHST columns.