Research on structural load-bearing systems exposed to elevated temperatures is an active topic in civil engineering. Carrying out a full-size experiment of a specimen exposed to fire is a challenging task considering not only the preparation labour but also the necessary costs. Therefore, such experiments are simulated using various software and computational models in order to predict the structural behaviour as exactly as possible. In this paper such a procedure, focusing on software simulation, is described in detail. The proposed constitutive model is based on the stress-strain curve and allows predicting SFRC material behaviour in bending at ambient and elevated temperature. SFRC material is represented by the initial linear behaviour, an instantaneous drop of stress after the initial crack occurs and its consequent specific ductility, which influences the overall modelled specimen behaviour under subjected loading. The model is calibrated with ATENA FEM software using experimental results.

<p>Generally speaking, adding a certain amount of steel fibres to a concrete mixture improves its mechanical properties. Currently, a lack of information considering tensile and post cracking behaviour of FRC at elevated temperatures is an issue to be faced. An experimental study of steel fibre reinforced concrete, also containing polymer fibres (FRC), subjected to high temperature is presented herein. Compressive strength, split tensile strength and ultimate bending strength were evaluated. Specimens were heated by the use of ceramic heaters and repacked for testing consequently. A finite-element based model was developed to predict the temperature distribution inside a specimen during both the heating and the cooling process.</p>

Purpose This work aims to present an experimental study of steel fibre-reinforced concrete (SFRC) subjected to high temperature, especially focusing on residual behaviour. Design/methodology/approach Compressive strength and split tensile strength of SFRC cubes and ultimate bending strength of prisms were evaluated under ambient and elevated temperatures. The specimens were heated by ceramic heaters and then repacked for testing. Findings The results showed that a compressive strength of SFRC is reduced by 38 and 66 per cent, tensile strength is reduced by 25 and 59 per cent and ultimate bending force is reduced by 33 and 56 per cent in case of 400°C and 600°C, respectively, comparing with ambient temperature. Originality value The developed testing procedure could be used for determination of material properties of SFRC under elevated temperatures.

Modelling the thermal response of timber is a primary issue for the assessment of the mechanical resistance of timber structures exposed to fire. Therefore, this paper analyses various advanced calculation methods of determining the charring rate. Authors of this contribution use analytical calculation methods according to two different publications and also a numerical calculation by means of program based on Finite Element Method (FEM). Input values of parameters in these calculations were derived from an experiment on a timber-concrete beam, which was realised by two authors of this paper in the past. In conclusion, the values of onedimensional charring rate of timber calculated by different methods are compared. It is necessary to pay attention to the fact that the resultant values can significantly differ depending on various input values in the analytical calculations. The charring rate increases until a certain time at the beginning of the charring and then it starts to slightly decrease. However, not all of the calculation methods presented in this paper correspond with that.

Purpose This paper aims to present a part of a coupled numerical model for prediction the fire resistance of elements in a horizontal furnace. Temperatures calculated inside the timber beam are compared to measured values from the fire test. Design/methodology/approach The paper presents a part of a coupled numerical model for prediction the fire resistance of elements in a horizontal furnace. The presented part lies in a virtual furnace which simulates temperature environment around tested elements in the furnace. Comparison of results show good agreement in the case when burning of timber is included in the numerical model. Findings The virtual furnace presented in this paper allows to calculate temperature environment around three timber beams. After validation of the fire dynamics simulator (FDS) model, the temperature conditions are passed to the FE model which solves heat transfer to the tested element. Temperatures inside the timber beam which are solved in software Atena Science are compared to measured temperatures from the fire test. The comparison of temperatures in three control points shows good accuracy of the calculation in the point closer to the heated edge. An inaccuracy is shown in points located deeper in the beam cross-section – below the char layer. Research limitations/implications In conclusion, the virtual furnace has a great potential for investigating the thermal behaviour of fire-resistance tests. A huge advantage inheres in the evaluation of the thermal effect throughout the volume of the furnace, which allows an accurate prediction of fire-resistance tests and evaluation of large number of technical alternatives and boundary conditions. However, passing the temperature field from the FDS model into FE model may decrease the level of accuracy. The solution lies in a coupled CFD-FE model. A weakly coupled model including fluid dynamics, heat transfer and mechanical behaviour is under development at Faculty of Civil Engineering, Czech Technical University in Prague. The fluid dynamics part which is presented in this paper is solved by FDS and the thermo-mechanical part is computed by object-oriented finite element model (OOFEM). The interconnection of both software is made owing to MuPIF python library. Practical implications The virtual furnace takes advantage of great possibilities of computational fluid dynamics code FDS. The model is based on an accurate representation of a real fire furnace of fire laboratory PAVUS a.s. located in the Czech Republic. It includes geometry of the real furnace, material properties of the furnace linings, burners, ventilation conditions and tested elements. Gas temperature calculated in the virtual furnace is validated to temperatures measured during a fire test. Social implications The virtual furnace has a great potential for investigating the thermal behaviour of fire-resistance tests. A huge advantage inheres in the evaluation of the thermal effect throughout the volume of the furnace, which allows an accurate prediction of fire-resistance tests and evaluation of large number of technical alternatives and boundary conditions. Originality/value The virtual furnace has a great potential for investigating the thermal behaviour of fire-resistance tests. A huge advantage inheres in the evaluation of the thermal effect throughout the volume of the furnace, which allows an accurate prediction of fire-resistance tests and evaluation of large number of technical alternatives and boundary conditions. However, passing the temperature field from the FDS model into FE model may decrease the level of accuracy. The solution lies in a coupled CFD-FE model. A weakly coupled model including fluid dynamics, heat transfer and mechanical behaviour is under development at Faculty of Civil Engineering, Czech Technical University in Prague. The fluid dynamics part which is presented in this paper is solved by FDS and the thermo-mechanical part is computed by OOFEM. The interconnection of both software is made thanks to MuPIF python library.