Modelos numéricos de vigas mistas de aço e concreto pertencentes a sistemas de pisos mistos de pequena altura em situação de incêndio / Numerical modelling of composite slim floor beams in fire

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

08/03/2012

RESUMO

Slim floor frames consists on structural system in which the steel beam is completely or partially inserted in a concrete slab, that is usually used in profiled steel decks systems. The main goal of the slim floor systems is to obtain a minimum height of the composite beam section and, consequently, achieve a higher height of the floor or a lower total height of the building. The partial encasement of the steel beam in the concrete slab provides a thermal protection, improving the behavior of the beam when subjected to fire. In order to evaluate the thermal and structural behavior of the slim floor system, numerical models considering partially encased beams, which can be found in the slim floor structures, were created. The numerical evaluation procedure was divided in two steps. In the first step, a two-dimensional thermal analysis is carried out using the general finite-element software TNO DIANA to obtain the temperatures gradient in the cross section during the fire exposure time and then, use the data in a computational code developed in FORTRAN which calculates the bearing capacity, over the exposure time, of the slim floor beams by means of the plastic moment capacity method, using the reduction factors associated to the mechanical properties of the materials presented in Eurocode 4. The second step consists in to develop three-dimensional numerical models using the software TNO DIANA and then obtain the complete structural behavior of the beam when subjected to a fire condition. Another aspect related to the loss of mechanical properties was also considered, such as the thermal expansion and the interaction between the steel and the concrete. In view of the DIANA functions, several models were developed in order to achieve a better approximation, a low computational cost, of some tests results presented in wide world literature. The cases of partial and complete interaction between the materials were analyzed, as well as the different constitutive models for them, so that the results obtained at the two steps were compared, and an evaluation of the methods was done

ASSUNTO(S)

análise térmica composite beam fire incêndio modelagem numérica numerical modeling pisos mistos de aço e concreto slim floor thermal analysis vigas mistas de aço e concreto

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