Buckling behavior of slender square concrete filled steel tubular columns strengthened with CFRP profile under combined compression and bending

Abstract

An innovative stub composite column consisting of square concrete-filled steel tubular (SCFST) column internally strengthened with a I-shaped pultruded CFRP profile, referred to as SCFST-CFRP column, has been developed. Research studies have demonstrated that this new stub column has the higher axial load capacity and ductility with the less weight in comparison to the SCFST column. Considering the use of slender column in the engineered systems, this study investigated resistance and behavior of slender SCFST-CFRP columns under the combined compression and bending. In the experimental program, the combined loading tests were completed on nine groups of specimens with varied slenderness ratios and load eccentricities. The column buckling behavior was analyzed in terms of failure modes, moment-curvature response, peak loads, longitudinal strain response, and strength reduction factors. The results addressed the differences in buckling behavior between SCFST-CFRP column and SCFST column. Finite element models were created and validated to evaluate influences of critical structural parameters on column resistance and provide supplementary numerical data. In addition, the tested and simulated results were utilized to assess the applicability of existing design approaches, as suggested in the AISC-LRFD specification, the GB50936 code, and empirical equations provided by Han, for the SCFST-CFRP slender column under the combined compression and bending. Validation results identified that the GB50936 code provided relatively accurate predictions of the slender column capacities under the combined loads, while the predicted capacity was not safe for the column with a large slenderness ratio. An improvement in the GB50936 design method was conducted using the test and simulation data for the SCFST-CFRP column under the combined compression and bending.