Fire Resistance Analysis Research Articles

Fire resistance analysis of reinforced concrete structures subjected to hydrocarbon fire exposure

Critical infrastructure facilities of Ukraine, in particular energy generating, are often the target of terrorist attacks by the Russian Federation army. Such facilities require engineering protection of buildings, structures, and roofs. The occurrence of fire may accompany destruction and damage to building structures due to explosive effects.Fires at critical infrastructure facilities are characterized by high intensity. The hydrocarbon fire curve is characterized by a rapid increase in temperature to 1100°C in the first 5 minutes after ignition.Fire resistance analysis according to a hydrocarbon fire curve can only be performed using advanced methods. Tabulated data and simplifiedmethods are given for standard fire only. This article presents the results of the fire resistance analysis of cast-in-place reinforced concrete walls, columns, and slabs for the hydrocarbon fire curve. The structures for the fire resistance analysis were taken as typical for protective structures around critical energy infrastructure facilities.Thermal analysis of structures subjected to fire that develops under the hydrocarbon fire curve: walls and slabs exposed to fire at one side and columns exposed to fire at four sides. The residual load-bearing capacity of reinforced concrete structures after fire exposure according to the hydrocarbon fire curve was calculated for their reduced cross-section.

Mechanical properties of bridge steel Q420qE at elevated temperatures

High-temperature mechanical properties of bridge steels, which were rarely investigated, are the foundation for fire resistance analysis and design of bridges. This study investigates the high temperature mechanical properties of Q420qE bridge steel by using steady-state tensile test method. Results indicate that this steel shows no yield plateau at both room temperature and elevated temperatures. Compared with the same grade structural steels, the decrease in elastic modulus and yield strength of Q420qE with increasing temperature are slower. However, the decrease of ultimate strength is more rapid, with a maximum difference on reduction factor being about 0.327 (41.92 %). The mainstream fire resistance design standards exhibit limitations in predicting the high temperature mechanical properties of Q420qE steel. Furthermore, predictive equations of mechanical property reduction factors of Q420qE at elevated temperatures were proposed, and constitutive model of Q420qE at elevated temperatures was recommended.

Numerical Analysis of Fire Resistance in Cross-Laminated Timber (CLT) Constructions Using CFD: Implications for Structural Integrity and Fire Protection

Fire represents a serious challenge to the safety and integrity of buildings, especially timber structures exposed to high temperatures and intense heat radiation. The combustibility of timber is one of the main reasons why regulations strictly limit timber as a building material, especially in multi-storey structures. This investigation seeks to assess the fire behaviour of cross-laminated timber (CLT) edifices and examine the ramifications for structural integrity and fire protection. Utilising computational fluid dynamics (CFD) simulations, critical variables including charring rate, heat emission, and smoke generation were analysed across two scenarios: one featuring exposed CLT and another incorporating protected CLT. The outcomes indicated that protective layers markedly diminish charring rates and heat emission, thereby augmenting fire resistance and constraining smoke dissemination. These revelations imply that CFD-based methodologies can proficiently inform fire protection design paradigms for CLT structures, presenting potential cost efficiencies by optimising material utilisation and minimising structural impairment.

Modeling and analysis of creep at elevated temperature analysis on thin-walled profile structures

Abstract High-strength steel plays a crucial role in aerospace because of its excellent performance. The high temperatures experienced during a spacecraft’s re-entry to Earth may result in creep in the steel, potentially leading to structural failure, so the finite element software is utilized in this paper to establish a calculation model and analyze the impact of temperature and fire duration on the creep strain of high-strength I-section steel beams under elevated temperatures. Among them, the high-temperature parameter significantly affects the creep strain variation of the mid-span element of the high-strength I-section steel beam. When the temperature parameter is increased by 100%, the maximum creep strain variation of the mid-span component of the beam will increase by about 24%. Under the exact increase, the maximum creep strain variation of the high-temperature duration parameter will only increase by about 3.78%; thus, when conducting a high-strength steel structure, fire resistance analysis should mainly consider the influence of temperature on its creep at elevated temperature strain.

Computational analysis of wildland fire resistance for transmission line tower

Finite element (FE) analysis of the transmission towers under a fire event and the accompanying wind is presented. Several key aspects (including temperature-dependent non-linear material properties, geometric non-linearity, member eccentricity due to the single-leg bolted connection, and the temperature-dependent connection behaviour in both the axial and the rotational directions) are considered. A quasi-static analysis is also employed in the FE model using the explicit solver available in Abaqus. The member temperature variation during a realistic fire event is derived analytically based on the fire intensity and the resultant vertical gas temperature distribution so that the effect of the realistic wildland fire can be input as a member temperature profile. First, fire design guidance in terms of the most critical heating and wind pattern, as well as the effect of fire-affected heights are provided based on the case study results. Then, further fire analysis is carried out to investigate the most critical fire scenario and to evaluate the vulnerability of the tower during a realistic fire event. Lastly, an evaluation of a commonly used spray-on thermal insulation and its effectiveness in reducing the member temperature and preserving ultimate strength during a catastrophic wildland fire event are presented. The FE simulations revealed that a 45-degree wind associated with partial side heating leads to a more critical degradation of the overall strength, whereas the effect of fire height is less obvious. In terms of the fire scenario, a longer fire duration associated with a slower wind is more critical for the fire resistance/rating.

A Circular Economy Perspective: Recycling Wastes through the CO2 Capture Process in Gypsum Products. Fire Resistance, Mechanical Properties, and Life Cycle Analysis

In recent years, the implementation of CO2 capture systems has increased. To reduce the costs and the footprint of the processes, different industrial wastes are successfully proposed for CO2 capture, such as gypsum from desulfurization units. This gypsum undergoes an aqueous carbonation process for CO2 capture, producing an added-value solid material that can be valorized. In this work, panels have been manufactured with a replacement of (5 and 20%) commercial gypsum and all the compositions kept the water/solid ratio constant (0.45). The density, surface hardness, resistance to compression, bending, and fire resistance of 2 cm thick panels have been determined. The addition of the waste after the CO2 capture diminishes the density and mechanical strength. However, it fulfills the requirements of the different European regulations and diminishes 56% of the thermal conductivity when 20%wt of waste is used. Although the CO2 waste is decomposed endothermically at 650 °C, the fire resistance decreases by 18% when 20%wt. is added, which allows us to establish that these wastes can be used in fire-resistant panels. An environmental life cycle assessment was conducted by analyzing a recycling case in Spain. The results indicate that the material with CO2 capture waste offers no environmental advantage over gypsum unless the production plant is located within 200 km of the waste source, with transportation being the key factor.

Fire resistance analysis and protection measures for cable components of suspension bridges

The growing number of vehicle fire incidents on suspension bridges poses a significant threat to the safety of the cable body components of these structures. This study focuses on the Longtan Bridge and employs a coupled Computational Fluid Dynamics-Finite Element Method (CFD-FEM) approach to recreate the environment of a tanker truck fire. A three-dimensional heat transfer model of the cable components and a structural fire resistance analysis model of the entire bridge are established. The study reveals the heat transfer patterns of cable components under a tanker truck fire and the evolution of the bridge structure's performance. Additionally, fire protection measures for cable components are proposed. The results indicate that during a tanker truck fire, the bridge deck exhibits a spatial transient temperature field, with temperatures around the cable components reaching 1170 °C, causing the highest temperature experienced by the steel wires on the cable surface to reach 736 °C. Under fire conditions, there is a redistribution of internal forces between the cables, with the fire-affected cable experiencing a decrease in internal forces and significant increases in adjacent cables' internal forces. The fire leads to plastic deformation in the fire-affected cable, resulting in permanent damage to the cables. When the number of cables broken due to fire at the midspan of the Longtan Bridge reaches six, the stress in the adjacent cables reaches 1861 MPa, exceeding the cables' ultimate tensile strength, leading to a progressive collapse of the entire bridge structure. The proposed heat-expansion fireproof coating and combination fire protection measures meet the regulatory requirements for fire resistance. It is recommended to apply a 3.5 mm thick heat-expansion fireproof coating on the main cable and cable components of the Longtan Bridge for fire protection. The research findings can serve as a reliable basis for establishing a fire protection system for the cable components of the Longtan Bridge.

Analytical modelling and critical temperature of circular CFST column exposed to standard fire

This paper establishes a finite element (FE) model for the fire resistance analysis of concrete-filled steel tubular (CFST) columns with circular cross section. The model is validated by experimental results from a database consisted of 123 fire tests on circular CFST columns. The critical temperature is clarified for the circular CFST column exposed to standard fire. The performance of circular CFST columns is discussed and extensive parametric study is performed by the FE model. The equation for the critical temperature of circular CFST columns to axial compression is proposed and compared with both FE and test results. The results show that the established FE model well captures the behaviour of CFST column exposed to standard fire, and the proposed critical temperature calculation method provides more accurate fire resistance predictions than methods in current codes of practice.

Analysis of fire extinguishing performance and mechanisms in transformer oil pool fires by large-scale compressed nitrogen foam: Impact of different nozzle pressures

This article investigates the suppression of transformer oil pool fires using compressed nitrogen aqueous film-forming foam extinguishing agents with varying nozzle pressures (0.1–0.4 MPa), and a comprehensive analysis of fire extinguishing behavior and resistance to re-ignition was conducted. The research findings indicate that at a nozzle pressure of 0.4 MPa, there is a significant enhancement in fire extinguishing efficiency, with a reduction in extinguishing time by 15.0%–29.2%, and an increase in resistance to re-ignition by 32.2%–48.2%, making it the optimal choice. In comparison to the 0.1 MPa condition, the maximum instantaneous emissions of CO and SO2 at 0.4 MPa are only 66.7%. The interaction of various effects, such as atomization, results in a significant enhancement of flame intensification and fire extinguishing effects when compressed nitrogen aqueous film-forming foam is sprayed at high nozzle pressures. The study provides valuable insights for firefighters in the practical use of foam extinguishing agents.

Parametric analysis of post-earthquake fire resistance of reinforced concrete frames without seismic design

To gain a deeper understanding of post-earthquake fire behaviour, 100 reinforced concrete (RC) frames representative of a building stock designed without considering seismic loading were modelled using the software SAFIR. A total of 4400 numerical analyses were performed to investigate the impact of different assumptions, such as the type of damage, damage location, number of sides of the RC elements exposed to fire, location of the fire and different fire curves on the post-earthquake fire resistance of the RC frames. Results showed that heavily damaged frames have significantly lower fire resistance compared to undamaged frames. Variations in the number of heated sides and fire locations were found to lead to significant differences in the time until the collapse of the RC frames. Moreover, due to increased demand for assistance following a large earthquake, rescue teams are likely to experience prolonged response times, exacerbating the potential for loss of life and infrastructure. Assuming parametric fire curves without firefighting efforts is a reasonable approach in post-earthquake events. This approach led to quicker collapse times compared to the standard fire curve ISO 834. This aspect combined with a lower fire resistance of the damaged structures can ultimately lead to the loss of lives and infrastructures. Therefore, a comprehensive understanding of post-earthquake fire behaviour becomes crucial for developing recommendations that can ensure the safety of RC structures in such events.

РАСЧЕТ ЭЛЕМЕНТОВ ЖЕЛЕЗОБЕТОННЫХ КОНСТРУКЦИЙ НА ОГНЕСТОЙКОСТЬ И ОГНЕСОХРАННОСТЬ В ПРОГРАММНОМ КОМПЛЕКСЕ СТАРКОН.

RCDiagra software as a part of the domestic STARKON software is presented. The software is designed to perform fire resistance and fire safety analysis of reinforced concrete beams and columns. The strength analysis is based on the nonlinear deformation theory and enables to take into account non-stationary thermal effects changing the concrete and reinforcement properties. To determine the ultimate strength, elastic modulus for concrete and reinforcement, ultimate relative deformations, a thermal analysis is performed in accordance with SP 468.1325800.2019 and MDS 21-2.2000. The thermal engineering analysis solve the problem of determining the temperature field in the beam cross-section under non-stationary thermal action, depending on the boundary conditions and thermophysical parameters of the material. It is assumed that the coefficients of thermal conductivity and specific heat capacity of concrete depend on the current temperature at the crosssection points.

Influence of talc particle size on the optical transparency, flame retardancy, and smoke release suppression of waterborne transparent fireproof coatings applied on wood surface

AbstractTalc with particle sizes of 1250 mesh (Talc‐1250), 3000 mesh (Talc‐3000), and 5000 mesh (Talc‐5000), used as synergist, was added into transparent fireproof coatings applied in wood substrates, and the influence of talc particle size on the comprehensive properties of the coatings was analyzed carefully. The results show that adding talc exerts super synergistic effect on enhancing the flame retardancy and smoke release suppression properties in the resulting coatings, and the synergistic efficiency of talc is varied with the talc particle size. Fire resistance analysis shows that the MTPPE2 coating containing Talc‐3000 exhibits better synergistic effects, accompanying a minimum back temperature of 106.3°C at 900°C and a maximum intumescent factor of 116.3. SEM‐EDS and FTIR analyses show that adding Talc‐3000 in the MTPPE2 coating contributes to the formation of a more intumescent and compact char against fire concomitant with the highest P/C mass ratio of 0.36 in char. Transparency analysis shows that the transparency of the coatings gradually decreases with the decrease of talc particle size, and the Talc‐1250 with exfoliated morphology imparts less loss of transparency to the coating while the Talc‐3000 and Talc‐5000 with intercalated morphologies induce more obvious light scattering in the coatings.Highlights Talc was used to enhance the comprehensive properties of transparent fireproof coatings. Synergistic efficiency of talc on the fire safety of coatings varies with its particle size. Talc with a particle size of 3000 mesh exerts an optimum synergism in the coatings. Transparency of the coatings gradually decreases as talc particle size decreases.

A Study on the Thickness of Fire-Resistant Spray of U-shaped Composite Beams through Fire Resistance Test and Analysis

Building fires can lead to loss of human lives and economic damage, as well as secondary damage due to collapsing buildings. Consequently, fire resistance performance of structural members has been garnering considerable interest in Korea. Fireproof structures are applied on the basis of the specification design. However, recent research results that focus on application of performance design have been published through a research project by the Ministry of Land, Infrastructure, and Transport. Therefore, in this study, composite beam specimens coated with fire-resistant material were manufactured, and fire resistance tests were conducted for 3 h. Additionally, finite element analysis was performed under the same shape and conditions to verify the reliability of the fire resistance analysis, which was conducted by varying the thickness of the fire-resistant coating.

Practical temperature calculation and fire-resistant design of special-shaped concrete-filled steel tubular columns

The fire performance of special-shaped concrete-filled steel tubular (SCFST) columns under axial load was investigated in this paper. The ABAQUS based finite element models were conducted for heat transfer and structural analysis. Twelve fire tests on SCFST columns under the ISO-834 standard fire curve by the authors' research were used to verify the model. In addition, heat transfer and fire-resistant mechanism of full-scale SCFST columns were studied; and extensive parametric studies were investigated to examine the influence of fire protection layer thickness, column limb thickness, slenderness ratio and other factors on temperature distribution and fire behavior of SCFST columns. Through the calculation and analysis of temperature field and fire resistance, a simplified temperature calculation method for steel tube, tension reinforcement, and inner steel plate are proposed along with the modularization temperature calculation method for special-shaped concrete sections. Moreover, the ultimate bearing capacity calculation method for SCFST columns under the standard temperature rise curve is proposed allowing for the influence of high temperatures on material properties, which can also be applied to determine fire resistance of SCFST column. Finally, the calculation method for the thickness of fire protection layer and the corresponding fire design is proposed based on the delaying temperature mechanism.

Numerical and Experimental Analysis of Fire Resistance for Bulkhead and Deck Structures of Ships and Offshore Installations

Investigating the loss of integrity (E) in cabin walls and decks, as well as the role of insulation capabilities, holds significant implications for preventing serious human, economic and environmental damage caused by the ignition of cabins in ships and ocean platforms due to fires and explosions. In this study, the fire resistance of A-60 class ship bulkheads and decks was evaluated through two groups of standard fire resistance tests. In the first test, the steel structure side of the bulkhead was exposed to the fire, while in the second test, the mineral wool and L-shaped stiffeners side of the deck was exposed to the fire. Numerical material models for steel and mineral wool were established based on standards, and the temperature distribution and structural deformation were simulated using Abaqus. The results showed a good correlation with the experimental data. The maximum and average temperature increases on the unheated surface of the bulkhead during the standard fire resistance test were 158 °C and 136 °C, respectively. The corresponding values for the deck were 176 °C and 138 °C. Upon the conclusion of the experiment, the maximum displacement deformation in the direction towards the furnace from the center of the cabin wall was 54 mm, and from the center of the deck, the maximum displacement deformation towards the furnace was 28 mm. This research can provide guidance for the design of fire-resistant ship compartment structures.

Fire Resistance Analysis of Two-Way Reinforced Concrete Slabs

This paper presents a fire resistance analysis of two-way reinforced concrete (RC) slabs. The study analyzes the effect of specific parameters—concrete cover thickness, span, and support conditions—on the fire resistance of the slabs. To that end, the slabs were exposed to Standard Fire ISO 834, and the 3D nonlinear numerical analyses were conducted in SAFIR2016. The results of the numerical analyses were evaluated against experimental results reported in the literature. The agreement between the two sets of results was satisfactory throughout the fire test. Nonetheless, to verify the obtained numerical results, all testing-related parameters must comply with the numerical simulation results. This comparison demonstrated the usefulness of numerical simulations in predicting the behavior of structures in fire conditions. In addition to the nonlinear numerical analysis, the fire resistance was calculated using the simplified method and tabulated data described in Eurocode 2 (Part 1.2) to assess the accuracy and reliability of fire safety regulations in the design of two-way slabs and identify significant differences between the design code and numerical analysis. The comparison showed that SAFIR2016 provides more accurate results by considering additional factors, such as tensile membrane forces, which increase the fire resistance of two-way slabs. According to the load-bearing criteria, the two-way slabs have high fire resistance, considerably higher than prescribed in the fire safety regulations, which ignore the positive effect of tensile membrane forces. According to the numerical analysis, the upper reinforcement in the compression areas of the slab's span was considered, which increased the fire resistance of the slabs. In contrast, according to the design codes, the contribution of this reinforcement is neglected. It was indicated that the increased concrete cover improves the fire resistance of the slabs. The vertical displacements increase by increasing the slab span, but according to the load-bearing criteria, all the slabs show fire resistance of over ten hours. In terms of bearing capacity, slabs with various support conditions show fire resistance of longer than ten hours. In terms of deflections, the supporting conditions of the slabs have a significant influence on their behavior. This study provides valuable insights into the fire resistance of two-way RC slabs and highlights the importance of considering specific parameters in the analysis. Doi: 10.28991/CEJ-2023-09-05-05 Full Text: PDF

Analysis of Fire Resistance of Prestressed Concrete T-Beam Based on ABAQUS Numerical Simulation

The analytical fire resistance calculations were carried out on 57 prestressed concrete T-beam models using the finite element software ABAQUS. The effects of different fire modes, different concrete strengths, different flange plate thicknesses, different ratios of the prestressing bar, and different concrete protection layer thicknesses were investigated in three cases with load ratios of n = 0.4, n = 0.6, and n = 0.8. The fire resistance of prestressed concrete T-beams shows a large variability under different fire modes. The fire mode significantly affects the fire resistance of the structure and should be given more consideration in the subsequent fire resistance design of the structure. The configuration of prestressing bars will significantly increase the fire resistance of concrete T-beams, while the thickness of the concrete protective layer and the concrete strength will significantly affect the fire resistance of prestressed concrete T-beams. Therefore, the fire resistance can be improved by adding prestressing bars, increasing the concrete strength, and increasing the thickness of the protective layer in the design. Finally, a fitting equation for fire resistance of the prestressed concrete T-beams based on the finite element model calculation data was created. The equation has good prediction accuracy and can provide a reference for the fire resistance design of prestressed concrete T-beams.

Fire resistance of low alloy Q420d high-strength steel column under high-temperature creep.

The high-temperature mechanical and creep characteristics of Q420D steel are investigated in this essay. To determine the steel's high-temperature yield strength, the high-temperature tensile test of Q420D steel was first performed. In the temperature range of 400°C-800°C, the high-temperature creep test under various pressures was conducted, and the creep strain curve over time was produced. Finite element analysis and comparison were done to examine the impact of creep strain on the Q420D steel column's bearing capacity under high-temperature conditions. The findings demonstrated that: Using Abaqus, a finite element fire resistance analysis of a Q420D steel column, was conducted while taking initial geometrical flaws, residual stress, and creep effect into account. As a result, the critical temperature of a Q420D steel column under various load ratios was determined. The largest deviation from the critical temperature in the standard GB51249-2017 was 2.9% when the creep effect was taken into account under the load ratio R = 0.3. The highest reduction in fire resistance limit time under low load ratio conditions, taking into account the creeping impact of Q420D steel columns, is 35%. The findings demonstrate that the high-temperature creep energy greatly lowers the steel column's fire resistance.

Simulation of nomograms showing the heating of steel structures with flame retardant coatings of different thicknesses (in the water)

Introduction. High temperatures cause deformation of steel structures which also lose stability and the bearing capacity, resulting in the collapse of structures with the subsequent collapse of the building. It is understood that intumescent paints are often used to increase the fire-resistance limits of steel structures up to R 90 and R 120. However the fire protection effectiveness of intumescent paints has not been sufficiently studied for the case of the long-term operation, and the application of this type of fire protection treatment of bearing steel structures requires justification. To ensure the building stability, coupled with the required fire resistance limit of structures, one should study the engineering factors affecting the fire resistance of steel structures that have intumescent paint coatings.Purpose of the research work. Development of approaches to simulation of nomograms demonstrating the heating of steel structures with flame retardant coatings of different thicknesses. The research work solved the following tasks:block diagrams of the research undertaking were developed to find the fundamental relationships between the dynamics of change in the structure of fire protection materials under thermal effects and the fire resistance limit of a building structure based on the choice of the functional criterion;mathematical models demonstrating dependence between the thickness of the dry layer of fire-retardant material were developed; the required fire resistance limit and thermo-physical characteristics of fire-resistant materials based on the experimental studies of the properties and effectiveness of fire-resistant materials were identified;nomograms showing dependences between the thickness of the dry layer of flame retardant materials and the flame retardant efficiency of flame retardants were made.Research methods. Hot Disk TPS 1500 thermal constant analyzer was used to analyze the thermo-physical characteristics of flame retardant materials. Thermal analysis was used to study the properties of flame retardants, as well as physical and chemical transformations occurring inside them under the programmed exposure to temperature effects and with the use of specialized thermal analysis equipment. The study of the fire protection efficiency for steel structures was conducted in accordance with GOST R (Russian State Standard) 53295–2009 “Fire protection means for steel structures. General requirements. The method of fire protection efficiency determination”.Results and their discussion. As a result of the research, an approach to prediction of the fire resistance of building structures was developed in the form of a research flowchart, used to choose the functional criteria. Experimental studies were conducted to identify mathematical dependences between the fire resistance and the indicators, which serve as functional criteria. In particular, when assessing the fire resistance of steel structures, a prediction is made on the basis of thermos-physical indicators. The authors were first to propose the introduction of the function of fire protection materials into the standard pattern of fire resistance analysis in the course of solving static and thermo-physical problems. The obtained data were used to make equations of dependence between the thickness of a dry layer of a fire-retardant material, the required fire-resistance limit of a structure, and the nomogram showing the heating of protected steel structures with fire-retardant coatings of various thicknesses.Conclusions. The results of the studies allowed identifying fundamental relationships between the dynamics of change in the structure of fire-retardant materials under the thermal effect and the fire resistance limit of a building structure on the basis of the choice of a functional criterion. Experimental studies of the properties and effectiveness of fire-resistant materials were conducted to develop a mathematical model showing dependence between the thickness of the dry layer of fire-resistant materials, the required fire-resistance limit and thermal-physical characteristics of fire-resistant materials.

CALCULATED ASSESSMENT OF FIRE RESISTANCE OF FIREPROOF REINFORCED CONCRETE BUILDING STRUCTURES BY PC LIRA-SAPR TOOLS

The paper outlines a method for numerical analysis of the stress-strain state in a fireproof RC structure with account of non-stationarytemperature fields in concrete and reinforcement for a standard fire temperature using the 'Thermal Analysis' system of the LIRA-SAPR program.The paper also describes the finite element models that enable the user to evaluate the effectiveness of fire protection in the structures and determine the ultimate fire resistance of RC structures.To illustrate the method, an analysis of a fireproof multi-cavity RC slab on fire resistance is taken as an example. The paper demonstrates the finite element models of fireproof building structures with fireproof coatings of various types. For such structures, an analysis of fire resistance is carriedout, and the temperature distribution is determined at nodes of the FE model. The physical and mechanical properties of materials are modified according to the temperature fields obtained. The bearing capacity of the structure is checked for force and temperature loads.The authors obtained the temperature distribution in the FE model of a fireproof RC slab at 120 and 240 minutes under a standard fire temperature.The results of the numerical analysis of unsteady heating of a fireproof RC slab in the LIRA-SAPR software were compared with experimental tests in a fire furnace. The convergence of experimental data and values obtained in analysis is satisfactory.The application of the proposed method makes it possible to accurately evaluate the fire resistance of reinforced concrete structures and predict their stress-strain state during a fire.