REINFORCED CONCRETE SLAB CALCULATION UNDER EXPOSURE TO INCREASED FIRE TEMPERATURES

Abstract

For the stress-strain state numerical researches of reinforced concrete floor structures considering non-stationary temperature fields in reinforcement and concrete at a standard temperature regime and a real fire temperature regime a method has been developed. A characteristics of the materials given in ДСТУ-Н Б EN 1992-1-2 are used as part of the methodology, as well as the necessary for the application of refined calculation method initial data. These data are established by available in literature experimental data analyzing and given in Eurocodes material characteristics. Assessing the structures fire resistance, the refined calculation method takes into account all the factors that have a significant effect on the structure stress-strain state during a fire. The increasing and distribution of temperature in the structure at a given moment in time (heat engineering calculation) and the mechanical behavior of the structure (static calculation) is determined, taking into account the corresponding fire scenario. The technique is illustrated by the reinforced concrete floor slab fire resistance calculating example. Calculations with the related thermal strength tasks implementation in the ANSYS software package have been carried out. The reinforced concrete floor slab design was carried out in the Design Modeller ANSYS software module.

Then, the calculations were carried out sequentially in the TRANSIENT THERMAL and STATIC STRUCTURAL modules. Concrete and reinforcement were modeled by volumetric elements. The approach does not require finite element mesh binding to the reinforcement spacing, which allows it to be applied to real dimensions’ tasks. In the concrete model, the yield surface consists of two intersecting Drucker-Prager conical surfaces. The calculation results are in good agreement with the presented literature experimental data. The proposed method usage makes it possible to assess the reinforced concrete structures fire resistance sufficiently accurate and predict its stress-strain state during fire.