Axial Loading Behaviour of Concrete Filled Steel Tube (CFST) Columns: A Parametric Study

Abstract

AbstractColumns built of concrete encased in filled steel tubes are known as concrete filled steel tube (CFST) columns. The use of CFST columns is common in tall constructions and long-span bridges. The ultimate load bearing capability of CFST columns gets affected by the D/t ratio, the L/D ratio and the steel grade. The diameter to thickness (D/T) ratio, length to diameter ratio (L/D) and steel grade are all used to evaluate a CFST column’s ultimate axial load bearing capability. CFST columns made of M30 concrete are available in three diameters: 100 mm, 125 mm and 150 mm having two thicknesses of steel tube: 4 mm and 5 mm. A consistent height of 600 mm is maintained for all CFST specimens. An experimental and numerical study was performed to analyze the behaviour of CFST columns under axial loading. As per the findings of parametric analysis, a CFST column’s ultimate loading capacity decrease as the ratio of D/t grows and rises as L/D ratio decreases. The improvement of 33.4% in loading capacity of CFST columns was observed with enhancing D/T ratio to 31.3 from 25 and 28.4% by changing D/T ratio to 37.5 from 31.3 with 4 mm external steel casing thickness. It was observed that for 5 mm outer steel tube thickness, when D/T ratio increased to 25 from 20, the loading capability was increased to 33.8%. Also, when the ratio D/T increased to 30 from 25 while keeping the same thickness of 5 mm, the loading capacity of the CFST columns increased to 28.6%. When L/D ratio was lowered from 6.0 to 4.0 and steel grade of the CFST column was improved, the CFST’s axial load capability was found to be increased by 52.7%.KeywordsCFSTAxial behaviourParametric study