Effect of bolted sgear connector on the axial load-bending moment capacity of columns

Hexagonal Concrete-Filled Steel Tubular (H-CFST) columns have been widelyregarded by engineers, especially in high-rise structures. The Gayoin FinancialBuilding in Tianjin and the Z15 Tower in Beijing were built in China with hexagonalcross-sections of CFST columns, with a height of 597 m and 528 m, respectively. Thelocal buckling in the thin-walled steel tube of these types of columns is a fundamentalproblem, which can be overcome to a large extent by Fiber-Reinforced Polymer (FRP)sheets. This paper is involved with nonlinear analyses and aims to numericallyinvestigate the mechanical performance of H-CFST short columns stiffened by FRPstrips under eccentric loads. First, to reserve consistency in the modeling, theexactness of finite element (FE) models was validated through the previous testresults, and a close agreement was obtained between them. Then, a systematicallyparametric study was developed to evaluate the impact of a multitude number of keyparameters on the strength of the columns. The ultimate load-bearing capacity of theeccentrically loaded columns was obtained, and the results were plotted as ultimateload-bending moment (P u -M u ) interaction diagrams. The confining contact stressmechanism between the steel tube and the concrete infill was thoroughly discussed, and it was found that the stress concentration at the corners of the H-CFST column isespecially significant. The findings displayed that using FRP sheets considerablyincreases the confinement effect of steel tubes to the core concrete and enhances thestrength of the columns by up to 35%. However, utilizing fully-wrapped FRP layersimproved the load-carrying capacity of the columns by a maximum of 55%. Finally, amodified design formula based on a unified theory was proposed to predict the ultimateload and bending moment capacity of H-CFST short columns subjected to eccentricloads.