Fire-resistant test and fire protection layer research of U-shaped steel–concrete composite beams

Abstract

Four U-shaped steel–concrete composite beams with channel connectors (CUSCB) were designed and tested under the ISO-834 standard fire curve and distributed vertical load. The research parameters included the fire protection layer thickness, the fire-resistance reinforcement in the U-shaped steel and the load ratio. The temperature distribution, fire resistance, and failure modes of the CUSCB specimen were investigated. The fire tests indicated that the failure mode of the specimen is flexural damage, the connection interface between the flange and web of composite beam remains intact. And the local buckling phenomenon did not happen on U-shaped steel. The fire resistance increased with the decrease of load ratio, and the configuration of fire protection layer and fire-resistance reinforcement. Then the numerical simulation was conducted to research the fire performance of CUSCB, and the simulation results of the temperature field and fire resistance were in good agreement with the test results. Moreover, a flexural bearing capacity calculation method for the U-shaped steel and concrete composite beam under standard temperature rise curve is proposed, which can be applied to calculate fire resistance. Finally, the calculation tables for the thickness of fire protection layer are proposed based on the delaying temperature mechanism.