Experimental behaviour of reinforced concrete (RC) beam to concrete-filled steel tubular (CFST) column frames subjected to ISO-834 standard fire

This paper describes six tests carried out on reinforced concrete (RC) beam to concrete-filled steel tubular (CFST) column planar frames subjected to ISO-834 standard fire. Each frame consists of two CFST columns and an RC beam with RC slab. These tests were meant to reproduce the conditions of the CFST columns and RC beams in multi-storey composite buildings commonly used in Chinese high-rise and subway constructions. The columns in four of the framed specimens used circular steel tubes while the remaining two used square tubes. Other test parameters include the level of axial load in the CFST column, the load level in the RC beam and the beam-to-column linear rotational restraint ratio. Temperature distributions on the composite column sections, beam sections and in the joint zones were measured during the tests. By analysis of the deformations and failures of the test specimens, differences between the fire behaviour of the CFST columns and RC beam members being in a frame and being isolated members are identified and failure mechanisms for the planar frames are proposed. The influences of different testing parameters on the limiting temperature of the planar frames are also discussed.