Fire resistance design of the bolted-welded hybrid composite connection in steel frame

ABS T R A C T As a key component of the steel frame, the connection is important for the behaviour of the steel frame and for the prevention of progressive collapse under fire. To investigate the fire resistance of the bolted-welded hybrid composite connection in steel frame (BWC-SF), based on a completed test, a refined finite element model of the BWC-SF with a reinforced concrete slab was established. A parametric analysis was carried out to investigate the effects of the beam end load ratio, axial compression ratio of the column, thickness of the beam web and flange, thickness of the column web and flange, thickness of the concrete slab and reinforcing bar diameter. The fire resistance of the connection improved with a decrease in the beam end load ratio and reinforcing bar diameter and with an increase in the thicknesses of the beam flange, beam web and concrete slab. The flexural capacity and stiffness of BWC-SF components, which had great effects on the fire resistance, were analysed. The flexural capacity and initial rotation stiffness calculation method of the BWC-SF at elevated temperatures were estab-lished based on the component method and verified according to the test and finite element results.