Experimental and numerical investigation on concrete filled steel tube columns reinforced with diagonal stiffeners under axial loading: Fid-Bau Portal

Experimental and numerical investigation on concrete filled steel tube columns reinforced with diagonal stiffeners under axial loading

Singh, Harpreet / Tiwary, Aditya Kumar

Abstract

Highlights • The proposed diagonal stiffened CFST columns had better axial ultimate load capacity than the unstiffened CFST section. • The proposed CFST section can achieve ultimate axial load-carrying capacity at a lower strain rate resulting in lesser deformation than unstiffened CFST. • The loading capacity of diagonal stiffener CFST columns increases with an increase in the diameter of the prop bar, yield strength of the prop bar, and the number of props. • The diameter of the prop had a great impact on the load–strain behavior of the proposed CFST section. • Diagonal stiffeners CFST columns reduce the lateral deformation of column section as compared with unstiffened section and eliminated the local buckling of steel casing.

Abstract In modern construction use of composite sections such as CFST columns was improved because of their numerous benefits in construction processes. However, some disadvantages like buckling of steel tube, poor corrosion and fire resistance necessitates the stiffening measures to be adopted. In this study, a novel stiffening scheme was proposed to use with unstiffened CFST column. The stiffening scheme is named as diagonal stiffeners which comprises diagonal stiffeners attached at diagonally opposite ends of steel tube. The stiffeners can be provided in three formats viz, binary, tertiary, and quaternary arrangement. In this paper the response of diagonal stiffeners CFST columns under axial compression was investigated through experimental program. The findings of the analysis were collected with regard to ultimate capacity, load vs strain response, and load vs deformation behavior. Further, to explore the performance of suggested stiffener arrangement, a FE model was developed in ABAQUS and validated through experimental findings. A parametric examination was conducted to evaluate the influence of diameter of stiffeners, number of stiffeners and its yield strength on the ultimate load capacity, load vs strain behavior, axial stress distribution in concrete, lateral deformation of column, and Poisson’s ratio of outer steel casing. Results of the analysis showed that CFST columns strengthened with proposed stiffening arrangements showed approximately 15–25 % higher ultimate load capacity than unstiffened CFST section. Also, using the diagonal stiffeners improved the pre-peak and post-peak behavior of column section. The local buckling of outer steel casing was eliminated and ductility of column section improved. It was deduced that stiffened CFST columns had better confining pressure on concrete infill and composite interaction between outer steel casing and infill concrete was enhanced. The prediction formula to anticipate axial load capacity was also established and can be employed to design of CFST with diagonal stiffeners.