Title:
Punching Shear in Fire-Damaged Reinforced Concrete Slabs
Author(s):
P. Bamonte, R. Felicetti, and P.G. Gambarova
Publication:
Symposium Paper
Volume:
265
Issue:
Appears on pages(s):
345-366
Keywords:
fire; punching shear; reinforced concrete slabs.
DOI:
10.14359/51663303
Date:
10/1/2009
Abstract:
Two-way flat slabs are extensively used in many structures, such as buildings, shopping centers, and parking garages, because their static efficiency allows to attain large span-depth ratios and to have more spaced columns. The
reduction of the thickness, however, is limited by serviceability requirements
(resulting from deflection criteria) and by the ultimate limit state of punching shear. This collapse mode has been widely studied in the past, with reference to ordinary conditions, but very limited attention has been devoted to the punching resistance of flat slabs in fire conditions, an issue which is of primary concern, especially in the case of parking garages.
This paper deals with two key aspects of slab punching in fire conditions. The
first is the sizable reduction of the punching resistance in a typical slab-column
assembly, because of the thermally induced damage caused by the exposure to the fire, that is modeled by means of the temperature-time curve ISO-834 (that fits very well the points given by ASTM E119-08a. The second is the sizable load increase due to the redistribution of the internal forces ensuing from the fire that is modeled through a realistic fire scenario based on the available information coming from real car fires.
Even if these two phenomena do not necessarily occur simultaneously in a real
fire, they both testify to what extent punching shear can be critical for reinforced concrete slabs in fire.