Post Fire Exposure Behavior of Concrete Filled Steel Tube Column under Axial Loading

Abstract

Concrete filled steel tube (CFST) columns are composite members consisting of concrete in filled steel tubes that are used as load carrying members. In the construction industry, CFST columns are generally preferred for the development of tall buildings and long span bridges. With the primary purpose of protecting human life and property during fire hazards, the present study aims at evaluating the behavior of CFST columns for post fire condition. In order to achieve this, concrete-filled steel tube (CFST) columns under greased and non-greased conditions are treated at elevated temperature of 600 °C and 800 °C and subsequently subjected to axial loading. newlineThe parametric variation for CFST columns with M30 concrete consists of three different diameters of 100 mm, 125 mm and 150 mm with two different steel casing thicknesses of 4 mm and 5 mm respectively. The columns are examined for both before and after fire exposures. For all the CFST specimens, a constant height of 600 mm is maintained. This study also checks the behavior of CFST columns under two separate cooling regimes (annealing and quenching) after exposure to elevated temperatures of 600 °C and 800 °C. newlineThe test results showed that load carrying capacity of non greased columns is slightly greater than greased columns it varies from 1% to 2.7% for all specimens. It was also observed that the elastic axial load capacity of non-greased columns was higher as compared to greased columns due to which the initial slope of load-deformation curve of non-greased columns were greater than the greased columns. The secant stiffness and ductility index of non-greased CFST columns was observed to be greater than greased columns. The secant stiffness of greased and non-greased specimens was varying from 18% to 59% and it was observed that the non-greased specimens have more ductility as compared to the greased specimens. newlineAlso, the results obtained by the experimental investigation of CFST columns for post-fire condition were compared with each other on the b