Experimental and numerical study on the flexural performance of composite beams with channel-section steel girder under fire exposure

To investigate the flexural performance of composite beam with channel-section steel girder under fire exposure, four specimens had been tested under four-points loading and ISO 834 fire exposure. The influence of load ratio, fireproof thickness and fire-resistant bars on the response of such composite beams have been investigated. It was shown that the deformation of composite beam without any fire protection increase rapidly until failure, and its fire resistance is only 23.4 min when the load ratio is 0.7. Decreasing the load ratio, increasing the fireproof coating thickness and adding the fire-resistant bars could effectively improve the fire resistance of such composite beams. Besides, the temperature distribution, the fire resistance under ISO834 fire exposure and the flexural capacity at elevated temperature of the specimen had also been studied by finite element analyses. After systematic parametric analyses, the calculation methods were proposed to predict the temperatures field and the flexural capacity of such specimens at elevated temperature, which agree well with the simulated and tested results.