Fire Scenario and Structural Behaviour in Underground Parking Garages

The objective of this paper is to investigate the main factors governing the fire behaviour of a typical underground garage roof consisting of a flat concrete slab supported by a number of relatively slender columns. On the basis of the available literature, and of reasonable assumptions, the fire scenario is worked out first, by properly modelling the temperature evolution in the ambient surrounding the structural members. This preliminary step is instrumental in solving the heat transfer problem from the ambient to the structural members. The calculated thermal field makes it possible to evaluate the decay of the mechanical properties as a function of the temperature. The stiffness decay, together with the thermal deformations, often brings in significant redistributions of the internal forces. The main factors are studied, and some general considerations are drawn on the overall safety of the structure under examination.