Behavior of concrete-filled square steel tubular stub columns stiffened with encased I-section CFRP profile under biaxial bending

Abstract

Concrete-filled square steel tubular (CFSST) stub column stiffened with an encased I-section carbon fiber-reinforced polymer (CFRP) is a new composite member that consists of a square steel tube, concrete infill, and an encased CFRP profile. This paper conducted investigations that experimentally and numerically examined the behavior of CFSST stub column with an inner I-section CFRP profile under biaxial bending. Seven column specimens were tested using biaxially eccentric compression tests in the experimental study. The parameters considered in the test were the load eccentricity, steel yield strength, and steel tube thickness. Numerical models were developed to investigate the column load-carrying mechanism using ABAQUS and validated against experimental results. Results indicated that the CFSST column stiffened with an encased CFRP profile has favorable capacity and ductility when subjected to biaxial bending. Furthermore, parametric analyses were performed to assess the effects of steel yield strength, concrete compressive strength, and steel ratio (steel thickness) on the load bearing capacity and P/Pu-M/Mu curve of stub column under biaxial bending. Finally, formulas to predict the P/Pu-M/Mu curves of the composite column under bi-axial bending were proposed in this study.