Steel Buildings in Europe

Part 6: Fire Engineering 6 - 41 5.2.2 Design models This model uses a holistic, rather than an elemental approach. It calculates the residual strength of the composite floors using yield line and membrane action, as shown in Figure 5.7. Figure 5.7 Yield line and membrane action of a composite floor in fire This design model takes account of the interaction between the components of the composite floor, and concludes that some beams may remain unprotected whilst maintaining the required level of fire safety. Thus, this design model gives a more economic and site-specific fire safety solution, with a significant number of steel beams of the composite floor left unprotected. This design model was calibrated against the fire tests, and is complemented by design tables and computer software. However, it demands expertise knowledge for the fire design of multi-storey buildings. Further information can be found in SCI publication P388 [6] . 5.2.3 Applicability The FRACOF design model may only be used to demonstrate the fire resistance of a partially protected structure where national building regulations permit the use of performance-based approach for fire design of buildings. In addition, this design model is only applicable to composite steel-framed buildings with the following limitations.  The frame is braced and not sensitive to buckling in a sway mode  Composite floor slabs comprise steel decking and reinforced concrete  Floor beams are designed to act compositely with the floor slab This model may not be used with precast concrete floor systems. Vertical support to edges of slab