Performance and damages of R.C. slabs in fire

Contrary to a common misconception, concrete structures are particularly vulnerable to fire, as witnesses by several cases of fire-induced collapses of buildings with a primary concrete structural system. Even when no collapse occurs, concrete elements are permanently damaged by the fire and may need to be repaired or substituted. Despite the economic losses that this implies, a procedure for assessing the level of fire damage is not indicated in the codes and this aspect is generally not considered in the design praxis. This paper presents a methodology for investigating the response of floor slabs with complex geometry exposed to fire and assessing the entity of the damage on the basis of the decrement of the load bearing capacity at the end of the fire.
By considering this quantity for different time of exposure to a standard fire, a curve is obtained that provides important information on the vulnerability of the slab to the fire action and can be used for optimizing the design on the basis of
the required class of resistance or for choosing between different slab alternatives.