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Coupled Systems Mechanics
  Volume 9, Number 2, April 2020 , pages 163-182

Thermo-mechanical analysis of reinforced concrete slab using different fire models
Samir Suljevic, Senad Medic and Mustafa Hrasnica

    Coupled thermo-mechanical analysis of reinforced concrete slab at elevated temperatures from a fire accounting for nonlinear thermal parameters is carried out. The main focus of the paper is put on a one-way continuous reinforced concrete slab exposed to fire from the single (bottom) side as the most typical working condition under fire loading. Although contemporary techniques alongside the fire protection measures are in constant development, in most cases it is not possible to avoid the material deterioration particularly nearby the exposed surface from a fire. Thereby the structural fire resistance of reinforced concrete slabs is mostly influenced by a relative distance between reinforcement and the exposed surface. A parametric study with variable concrete cover ranging from 15 mm to 35 mm is performed. As the first part of a one-way coupled thermo-mechanical analysis, transient nonlinear heat transfer analysis is performed by applying the net heat flux on the exposed surface. The solution of proposed heat analysis is obtained at certain time steps of interest by a-method using the explicit Euler time-integration scheme. Spatial discretization is done by the finite element method using a 1D 2-noded truss element with the temperature nodal values as unknowns. The obtained results in terms of temperature field inside the element are compared with available numerical and experimental results. A high level of agreement can be observed, implying the proposed model capable of describing the temperature field during a fire. Accompanying thermal analysis, mechanical analysis is performed in two ways. Firstly, using the guidelines given in Eurocode 2 - Part 1-2 resulting in the fire resistance rating for the aforementioned concrete cover values. The second way is a fully numerical coupled analysis carried out in generalpurpose finite element software DIANA FEA. Both approaches indicate structural fire behavior similar to those observed in large-scale fire tests.
Key Words
    Thermo-mechanical analysis, reinforced concrete slab, fire loads, standard ISO 834 fire curve, parametric fire curves, structural fire resistance
Samir Suljevic: Faculty of Civil Engineering, University of Sarajevo, Patriotske lige 30, 71000 Sarajevo,
Bosnia and Herzegovina; Université de Technologie de Compiègne/Sorbonne Universités, Laboratoire Roberval de Mécanique, Centre de Recherche Royallieu, 60200 Compiègne, France
Senad Medic, Mustafa Hrasnica: Faculty of Civil Engineering, University of Sarajevo, Patriotske lige 30, 71000 Sarajevo, Bosnia and Herzegovina

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