A simplified method for analysis of reinforced concrete beams exposed to fire situation

The reinforced concrete structural design consists in determining the structural members dimensions, steel ratio and location of steel rebars so that a limit state is not reached. Currently, when considering fire effects, commercial design software, in general, are limited to do the verifications only based on the tabular method, according to ABNT NBR 15200, without considering internal and external forces, so the designer needs to change the dimensions of the concrete section. This fact does not stimulate the use of the Brazilian standard codes since they do not present economic solutions. This paper aims to propose a simplified method to design reinforced concrete beams, of harbor structures, in a fire situation, which allows the implementation in commercial design software. Such proposed simplified method intends to involve structural safety, improves design facilities and economy in construction. Then, through a numerical example, the practical application of the tabular and simplified method was demonstrated. The results obtained by the simplified method were more economical than the tabular method. The calculation models validation was done through a comparative study with values found in the literature, as well as those calculated by the 500 °C isotherm method, and with the software ANSYS results. At the end of this work, it was concluded that the proposed simplified method, besides this being a method that allows an easy application, presents results, in general, in favor of safety; and, withal, allows more economics results when compared with the tabular method.