Post-fire material properties of stainless-clad bimetallic steel

An experimental programme is carried out to investigate post-fire mechanical properties of 316L austenitic stainless-clad (SC) bimetallic steel plates. A total of 63 coupons are tested under monotonic tension forces after cooling down (cooling in air and in water, respectively) from elevated temperatures ranging from 100 degrees C to 1000 degrees C. Based on the test results, a number of post-fire stress-strain curves and associated mechanical properties (elastic modulus, yield strength, ultimate tensile stress and elongation percentage after fracture) are obtained. In addition, retention factors of the material properties compared with those at ambient temperature are also determined. It is found that effects of the cooling method on the post-fire mechanical properties of the SC bimetallic steel are significant when compared with that at ambient temperature if the steel has been exposed to temperatures above 600 degrees C. The post-fire elastic modulus varies slightly with the heating temperature for both cooling conditions in air and in water. For the post-fire yield strength, ultimate tensile stress and elongation percentage after fracture, they generally decrease under the cooling condition in air, but increase under the cooling condition in water with an increase in the value of the heating temperature. Hence, new equations are proposed to describe the post-fire mechanical properties of the SC bimetallic steel, and effects of the clad ratio is incorporated. The research outcomes herein will allow structural and fire engineers to make accurate and reliable predictions on structural performance of such steel, and provide valuable reference for further research at the level of members and structures.