Structural response of unprotected and protected slim floors in fire

Slim floor systems are a latest addition to the existing construction types and are currently being used for various construction purposes. Preference of slim floors over traditional composite floors is due to their ease of construction, when combined with steel decking. Considerable amount experimental work on fire response of slim floors has been conducted since 1980s. Though, these floors offer a better fire resistance, however, fire protection materials including intumescent coatings are often used in situations where a higher fire resistance is desired. Fire tests have also been conducted to analyse the performance of intumescent coating applied on steel elements as a protection material. This study presents a finite element analysis approach to model the behaviour of unprotected and protected slim floors in fire. Initially, FE analysis has been performed to model the thermo-mechanical behaviour of unprotected slim floors and results obtained have been verified against the reported test data. In the middle part, thermal behaviour of an intumescent coating, applied on a steel element as a fire protection, has been modelled and verified. The verified models have finally been combined to perform thermo-mechanical analysis for slim floors protected with intumescent coating. Results show that the protected slim floors offer a higher fire resistance as the temperature of the steel section remains within 400 °C even after 60-minute standard fire exposure. Lower temperatures in steel result in lesser reductions of strength and stiffness, hence, the protected slim floors undergo lesser deflections and offer higher fire resistance.