Civil Engineering Association

The main parameters to be considered in this research programmer i.e. geometrical factors (shapes, buckling lengths), steel qualities and coefficients governing the heat exchanges are presented first. The temperature dependent stress-strain relationships of steel as initially existing in the program OEFIC0SS have been tested by simulation of bending tests described in the litterature. It has shown a necessity to improve these laws when pure steel elements have to be calculated. New improved stress-strain relationships of steel have been carried out and calibrated thanks to transient state beam tests performed on small simply supported steel beams, subjected to a concentrated constant load, and submitted to a controlled temperature increase. These new laws have been established as well for commonly used construction steels as for high strength steel FeE 460. The validity of these improved relationships has been next verified by simulating very well six full scale fire tests performed on unprotected steel columns in the laboratories of Braunschweig and Gent. The possibility to take into account a distribution of residual stresses has been introduced in CEFICOSS. The simulation of the six column tests showed that residual stresses have a quite small influence of the fire resistance time of columns. It has been decided, however, to consider systematically a distribution of residual stresses in the calculations. Practical design tools have been finally carried out and are proposed in form of tables as well as diagrams.