Colunas mistas parcialmente revestidas: efeito da resistência e rigidez na resistência à flambagem sob ação do fogo

Abstract

Composite columns, partially encased with concrete, present a better structural performance than bare steel columns. The concrete between the flanges, increases the fire resistance of the column, besides the strength and stiffness, being necessary to determine this property for this type of structural element. The Eurocode 4, in the annex G, presents a simplified calculation method to determine the fire resistance of the partially encased columns, calculating the buckling resistance, around the weak axis, when exposed to the standard fire curve. Studies developed by A. Fellouh and improved by L. Calió, concluded for unsafe results when using the Eurocode, proposing new equations and parameters for the balanced summation model presented in the annex G. This study aims to propose a new improvement for the simplified calculation model, using new formulae, based on thermal transient nonlinear simulation result, developed with the software ANSYS. This investigation deals with thirty different cross sections of partially encased columns, being ten of each specified for the profile series, HEB, HD and UC. The numerical simulation results were used to improve the model, being this solution compared with the current version of Eurocode. The results obtained with the current proposal model present safer values when compared with the current version of Eurocode. There is a good agreement between the numerical results and the new proposed solution model.