Behaviour of continuous concrete filled steel tubular columns loaded eccentrically in fire

Abstract

Concrete filled steel tubular (CFST) columns used in multi-storey buildings are generally designed as continuous members all over the world. This research has focused on the behaviour of eccentrically loaded continuous columns in fire, through the standard fire furnace testing of twelve CFST square columns of 3.2 m length. The tests covered three different types of infill; plain concrete, bar reinforced concrete and steel fibre reinforced concrete, with the columns subjected to compressive load levels ranging from 0.33 to 0.41. The result shows that, the significant initial expansion of the steel tube relative to the concrete reported by many researchers did not eventuate, due to the restraining effect of the unheated column between the furnace and the end supports. This represents a typical continuous column in a multi-storey building where the column above and below the floor on fire remains cooler. The use of conventional reinforcement increased the FRR of the column compared to using steel fibre or plain concrete infills. Using the experimentally measured fire resistance rating, the axial capacity in fire was calculated in accordance with DR AS/NZS 2327 and EN 1994-1-2 and it was shown that the code is too conservative for all continuous column loaded eccentrically. © 2017 Elsevier Ltd