Experimental Study on Mechanical Properties of High Strength Q460 Steel After Foam Extinguishing
CHEN Guangpeng1, ZHANG Chuntao1,2
1 School of Civil Engineering and Architecture, Southwest University of Science and Technology, Mianyang 621010, China 2 Shock and Vibration of Engineering Materials and Structures Key Laboratory of Sichuan Province, Mianyang 621010, China
Abstract: High strength Q460 steel is extensively used in building construction due to its potential benefits over high strength and cost efficiency. Its performance in fire is very important to assess the extent of its fire damage and reusability. This paper presents the details of an experimental investigation on the post-fire mechanical properties of high strength Q460 steel after air and firefighting foam cooling. Tensile tests are performed on specimens exposed to elevated temperatures varying from 200 ℃ to 900 ℃ and then cooled down to room temperature in air or in extinguisher foam. The results from this investigation provided post-fire stress-strain curves, yield strengths, ultimate strength, elastic modulus, ultimate elongation and their residual factors. Systematic comparative analysis for the differences of mechanical properties of Q460, Q690 and Q235 steels are carried out. Significant differences are observed on the surface after exposing different high temperature and cooling in various media. The inf-luence of high temperature and cooling methods on elastic modulus is negligible, while sharp reduction is especially noted in the yield strength, ultimate strength and ultimate elongation. In addition, it is found that the loss of mechanical properties of Q460 steel is negligible for exposure tempe-rature up to 500 ℃ and cooling in air or in extinguisher foam. When exposed to 900 ℃, the yield strength, ultimate strength and ultimate elongation of high strength Q460 steel cooling in air are able to retain 38%, 67% and 107% of their ambient temperature capacity, whereas the yield strength, ultimate strength and ultimate elongation after foam extinguishing can retain 39%, 67% and 131% of their ambient temperature capacity. Finally, predictive equations are proposed for simple evaluation of post-fire material performance of Q460 steel. The results can be used to eva-luate the mechanical performance of Q460 steel structures after fire.
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2021, Vol. 35 
