Fire resistance of composite slim floor beams

Abstract

There is an increasing interest in the steel-concrete composite slim floor construction in the Nordic Countries and the UK. The slim floor beams, which are partly contained within the floor slab, have inherent good performance under fire. At the moment, a new type of slim floor beam is under development in Finland. In this paper, the thermal and structural performance of this new slim floor beam is investigated under fire by using numerical analysis programs. The temperature analysis and calculations of the load-bearing capacity are carried out under fire conditions (both ISO standard fire and natural fire) according to Eurocode 1 Part 2.2. The structural fire resistance behaviour of this new slim floor beam is investigated and the relationship between the fire resistance time and load ratio under ISO standard fire is discussed. Moreover, the minimum load ratio of the beam under a natural fire is analyzed. The critical relationship between the minimum load ratio and the fire parameters (opening factor and fire load density) is also established, provided that the structural failure is caused by a reduction in the flexural capacity of the fire-exposed beam.