Parametrical study on the behaviour of steel and composite cellular beams under fire conditions

This paper describes an extensive parametric study on the behaviour of cellular beam under fire conditions. Different finite element models using shell elements were developed considering both material and geometrical non-linearity; CAST3M [1], ANSYS [2] and another one in SAFIR [3]. They were calibrated on the basis of a new experimental test campaign performed in the scope of the project FICEB+ [4] funded by the Research Fund for Coal and Steel The comparison between the finite element prediction and actual experimental results showed a good agreement in terms of failure modes, load deflection relationship and ultimate loads. At failure, temperature measured during the fire tests indicated that failure arising by web post buckling of cellular beams in fire cannot be simply estimated by applying temperature dependent reduction factors on strength alone, as given in codes. A design model representing the behaviour of cellular beam in fire conditions has been developed by Vassart [5-7]. This design model is able to predict the complex behaviour of cellular beam in case of fire comprising web-post buckling and Vierendeel bending, as well as standard flexural bending. The results of the Finite Element Models are compared in terms of critical temperatures and failure mode obtained using the design model. This paper also contains some tests results that were used to calibrate the FEM model and the comparison between analytical and FEM models.