BEHAVIOUR OF STEEL-CONCRETE COMPOSITE COLUMNS (CFT)

Abstract

The steel tube in a Concrete Filled Tubular Column (CSFT) acts as both longitudinal and lateral reinforcement, and is thus subjected to biaxial stresses. The advantages of CSFT over other composite members are that the steel tube provides formwork for the concrete as well as the filled-in concrete prevents local buckling of the steel tube wall and concrete spalling can be avoided. As a whole, the stiffness of the member increases due to composite action compare to conventional steel members. The confinement effect is also playing a big role on the load carrying capacity of CSFT. An experimental study was conducted to understand the behavior of Short Concrete Filled Steel Tubular Columns (CSFT) under axial compression failure. A total of 35 specimens having different cross-sections and filled with different grade of concrete were axially tested to investigate the load carrying capacity. These specimens were tested to study the behaviour of CFT column for different D/t ratio and concrete strength. Study of development of strain field on surface of steel concrete composite columns with the - help of Digital Image Correlation Technique is also performed. A new kind of composite column, Concrete filled double skin tubular (CFDST) which consists of two steel tubes was also studied.