Three-dimensional modelling of two full-scale fire tests on a composite building

Because of the high cost of fire testing it is becoming increasingly important to have analytical methods that can predict the behaviour of structures when subjected to fire conditions, In recent years a computer program, VULCAN, has been developed at the University of Sheffield for the three-dimensional structural analysis of composite and steel-framed buildings in fire. In this paper the main features of the program are outlined and two full-scale fire tests at Cardington are modelled using VULCAN to demonstrate the current capability of the program. A number of parametric studies were carried out to investigate the influence of the rigidity of the connections used and the floor slab details on the behaviour of the structure in fire conditions. The comparisons simply validate the model. However, the parametric studies provide evidence that when steel temperatures are less than 300 degrees C the concrete slab has little influence, other than to play a part in generating thermal curvature in composite beams. For temperatures higher than about 500 degrees C the effect of the slab is much greater and it is the slab thickness which is the most important influence on the behaviour. At very high temperatures the floor slab becomes the main load-bearing element, whose strength and stiffness are crucial to the integrity of the fire compartment.