Abstract
This paper reports an experimental study on the mechanical performance of concrete encased steel (CES) stub columns after exposure to high temperatures. A total of 81 CES stub columns are tested, including 77 specimens that are heated for different durations and 4 that are unheated. Each test examines the influences of volume-stirrup ratio, heating duration, fire resistant coating thickness and cooling method (air-cooled and water-quenched) on the strength, deformation, elastic modulus and ductility characteristics of specimens. Findings show that heating duration and fire-resistant coating thickness have the greatest effects on the mechanical response of CES stub columns. The effects of volume-stirrup ratio and cooling method decrease in turn. The residual strengths of post-fire CES stub columns are positively related to volume-stirrup ratio and fire-resistant coating thickness and negatively correlated with heating duration. Without fire protection layer, CES stub columns on average retained 0.89, 0.76, 0.58 and 0.5 times of the original strength after exposure to high temperature with heating durations of 0.5 h, 1 h, 1.5 h and 2 h. After being protected by fire-resistance coating of 16 mm thick, the strengths on average only decrease by 5.45%, 5.96%, 13.81% and 20.38%, respectively. Water cooling on average decreases the resistance to compression by 5.6% compared with natural cooling. Finally, formulae are suggested for predicting the ultimate strength of CES stub columns after exposure to high temperature. It is verified that the calculated values from the formulae are in good agreement with the experimental results.
Published Version
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