CALIBRATION OF A SIMPLIFIED METHOD FOR FIRE RESISTANCE ASSESSMENT OF PARTIALLY ENCASED COMPOSITE BEAMS

摘要

This paper is devoted to evaluate the fire resistance of partially encased composite beam subjected to fire from beneath by using different analysis methods.In particular, for the evaluation of the sagging and hogging moment resistance, Eurocode 4 (EN1994-1-2) suggests two different simplified methods: -the "general simplified method": a specific thermal analysis provides the temperature field and the subsequent mechanical analysis is performed according to the plasticity theory;-the "simplified method"proposed in the Annex F (E.1 and E2): the mechanical analysis is carried out applying the plasticity theory and the effect of temperature is taken into account by reducing the size of the parts that make up the cross section and/or by reducing the mechanical properties of materials by means of reduction factors (both provided as function o f fire exposure time).The reliability check of the simplified method proposed in the Annex Fand the proposal of further alternative simplified methods are discussed within the activities of Evolution Group of EN1994-1-2, of which some of the authors of this paper are members.Therefore, in order to evaluate the reliability of the simplified method proposed in the Annex E the moment resistance, for a fixed fire exposure time, has been calculated by an advanced calculation method (incremental-iterative) based on the construction of the Moment-Curvature diagram, with reference to several case studies, within a parametric analysis.A comparison between simplified and advanced method has been carried out and, based on the noticed criticism, an alternative simplified method, easy to implement and more reliable, has been processed.