Application of Idealized Materials Data for Calculation of Fire Exposed Concrete Constructions

The author has developed a system of methods for calculation of the load bearing capacity of concrete constructions at any time of any fully developed fire including the time of maximum temperature of a standard fire as a special case. The methods have been derived based on materials data from 180 test series from the literature and test series of 300 specimens made by the author and heated slowly in traditional ovens or rapidly by means of microwave power. Furthermore the methods have been compared to a great number of full-scale tests including 50 column tests and additional tests of slabs and walls have recently been made extending the field of application to light aggregate concrete constructions as well. The Eurocode ENV1992-1-2 and the Danish code for concrete constructions DS411 have adopted the basics of the methods; but these codes are mainly focused on standard fire performance and do not provide the means necessary for taking the severe drop of load bearing capacity in the cooling phase into account. The paper describes how the methods can be applied for fully developed fires, and especially how the methods can be incorporated into a performance based design. A brief description is given of the basic processes deteriorating concrete at elevated temperatures, and examples of idealized mechanical properties are given for a variety of concretes spanning from fire resistant concrete over heavy concretes with different aggregates to light aggregate concrete. It is explained how these data can be applied for deriving reduced cross sections and for calculating the anchorage capacity of reinforcing bars. The paper does not intent to be a full reference for the methods, but to introduce the basis of them, indicating sources of further information and discussing the differences between these methods and possible other approaches.