NUMERICAL STUDY ON PERFORMANCE OF CIRCULAR CONCRETE FILLED STEEL TUBE OF SLENDER COLUMNS UNDER ECCENTRIC LOADING.

Abstract

Concrete-filled steel tube (CFST) columns are greatly efficient categories of composite columns. Their numerous advantages, apart from its superior structural performance making a typical composite frame structure. Despite, most of previous research works had been limited to structural behavior of short CFST column under axial loads. But Currently, modern engineering structures of CFST widely developing throughout the world on slender column due to they have more advantages in practical area and this thematic area are needs to interesting for further study. This study would aimed to compare the performance behavioral of circular concrete-filled tube of slender column having various cross sectional configuration subjected to eccentric loading. The primary parameters which would considered in the study are diameter to -thickness of steel tube ratio, length to diameter ratio, eccentricity ratio and concert to - steel grade ratio. The finite element program ABAQUS software package are be used to construct a finite element model subjected to eccentric loading. The results of the finite element analysis are compared with experimental tests to obtain the validity of the finite element model and its reliability. The analysis result assures that the effect of eccentric loading on variation of the all parameters in used, to begin with increase the percentage of length to diameter ratio by 2 times decreases the ultimate bearing capacity approximately from 2.96-13.89 %. In addition to the ultimate bearing capacity is decreases by nearly 37.17% when eccentricity loading is increasing by 20%. The inserted steel section can help to enhance the energy reserve, in terms of the ultimate bearing capacity. Thus, CFDST has relatively 15% more in comparison with nominal CFSTDS slender columns under eccentricity loading whereas the CFST has nearly 3% lower. Besides, incorporating additional steel has impact on the global buckling mode failure of slender columns: when additional steel is provided, the mode of global buckling increases. It is also found that as we decrease the diameter to steel thickness ratio by one and half increases the bearing carrying capacity up to 65.58%. Through increasing the strength of steel to concrete ratio by 3 times, the ultimate bearing capacity of slender CFST columns has been improved from 8.72 to 23.70%. Furthermore, as the percentage of eccentric ratio increases by 2 times, the lateral displacement of the slender CFST column decreases by 7.59%