Fire Resistance Of Building Structures Research Articles

Влияние режима пожара на огнестойкость несущих строительных конструкций машинных залов ГРЭС

Machine rooms of a state district power plant (GRES) are sizeable. Heat impact on the structures of the building in the case of a real fire can significantly differ from the impact in the case of a standard fire. Therefore, the calculation of fire resistance of building structures should be conducted not only in conditions of a standard fire but of a real fire as well. The objective of the study is the theoretical evaluation of the actual limits of fire resistance of load-bearing building structures of the machine room of the main building of the Nizhneturinskaya GRES in conditions of standard and real fire regimes. Numerical experiments to calculate the heating of load-bearing building structures in the case of a standard fire and the case of the most hazardous scenario of the real fire development have been conducted in the framework of the study. A field 3-dimensional model to calculate fire hazardous factors and a non-stationary thermal conductivity equation have been applied. The obtained results have been analyzed. The field model adapted to the space-planning solutions of the machine room has been described. The most hazardous scenario of the development of real fire in case of combustion of the turbine oil spill in the sector of the machine room with the lowest height of ceiling has been chosen. The temperature fields in the gaseous environment of the machine room at different moments are presented. It has been detected that the heating of reinforced concrete structures of the machine room ceiling is significantly uneven due to the 3-dimensional gas dynamic pattern of fire. Dependencies of temperatures of the frame of reinforced concrete load-bearing structures of the ceiling on the time of standard and real fires in the most heated section of the ceiling have been obtained. It has been determined that the maximum temperature of the frame in the case of the standard fire is lower than in the case of real fire. Due to the features of the 3-dimensional thermal gas dynamic pattern of fire in machine rooms of the GRES, the fire resistance of load-bearing building structures in these premises must be determined in both conditions of standard fire and real fire, considering the most hazardous scenario of its development.

Environmentally safe installation for determining the fire resistance of coatings and fire resistance tests of small fragments building structures

Actuality. Taking into account fire statistics, the task of preventing the occurrence and spread of fires is urgent. It is obvious that the fire resistance of building structures, which must be taken into account at the design stage, is of the greatest importance and influence on the development and spread of fires in buildings and structures. Conducting fire experiments makes it possible to obtain the most complete information about the behavior of building structures under fire effects, however, the scale of field tests, labor-intensiveness, energy consumption and damage to the environment prompts the search and development of alternative methods that would ensure the environmental friendliness of the tests, compliance with the conditions of the experiment ( standard fire temperature regime), and at the same time would make it possible to estimate the limit of fire resistance of a building structure in reduced dimensions or to experimentally determine the fire-resistant ability (efficiency) of fire-resistant coatings. Purpose. The main goal of the article is rationale use of an installation for determining the fire-resistant capacity (efficiency) of fire-resistant coatings and fire resistance tests of small-sized fragments of building structures, taking into account the reduction of the harmful load on the environment. Main results. Research has been carried out and the design features of the installation have been substantiated, the principle of which is to heat the inner space of the chamber with the help of electric heating elements, which, unlike liquid fuel (diesel fuel, fuel oil, gas), do not harm the environment. A control unit-module of variable voltage regulation designed to regulate the heating temperature of the radiation panel in the test chamber has been developed. The design of the created test setup makes it possible to increase or decrease the temperature on the heating surface of the test sample, not only with the help of the heating temperature regulator, but also in manual mode, by moving the test sample closer or further away from the radiation panel along the guides. Conclusions. According to the results of experimental tests, it was established that the chamber of the installation warms up uniformly and according to the standardized temperature-time dependence Ts = 345lg (8t+1)+20). At the same time, the temperature regulation process using BP-10 with triac output ensures stable operation of electric heating elements up to temperatures of 1000 °C. A feature of the created installation is the possibility of additional lowering or raising of the temperature on the heating surface of the experimental sample, in case of its deviation during the experiment, by means of approaching or moving away from the sample to the heating panel. The conducted studies confirm the necessary reproducibility of experimental results.

METHODOLOGY FOR STUDYING THE FIRE PROTECTION ABILITY OF A FIRE PROTECTION COATING BASED ON POLYSILOXANE AND OXIDES OF ALUMINIUM, TITANIUM, AND CHROMIUM FOR STEEL BUILDING STRUCTURES

Fires and their negative consequences are a significant problem today. The final report of the World Fire Statistics Centre in 2023 shows that an average of 3.7 million fires occurred annually between 1993 and 2021. The fire resistance of building structures has paramount importance and influence on the development and spread of fires in buildings and structures, which needs consideration at the design stage. Particular attention should be paid to metal structures when used in construction since their fire resistance limit is about 15 minutes, depending on the profile and cross-section of the structure, and this, in turn, limits their use in buildings and structures where the fire resistance class of structures is REI 15. A way to increase the fire resistance class of a steel building structure is its fire protection implemented using dedicated means that protect the steel structure from the effects of high fire temperatures. The study aims to develop a methodology and determine the heating time of prototypes of steel plates with a fire-retardant coating based on polysiloxane and oxides of aluminium, titanium, and chromium to a critical temperature depending on the coating thickness (0.3, 0.45, 0.6, 0.8 mm) and the thickness of the steel plate (0.3, 0.5, 0.8 cm). To determine the fire protection capacity of the developed fireproof coating, we used the method regulated by clause 7.4 of DSTU-N-P B V.1.1-29:2010 ‘Fireproof treatment of building structures. General requirements and control methods’. The authors have developed a methodology for conducting experimental studies of the effectiveness of fire protection coatings using an installation for determining the fire protection capacity (effectiveness) of fire protection coatings, the principle of which is to heat the interior of the installation chamber using electric heating elements. The heating time of the prototypes of steel plates with the developed fire protection coating to the critical temperature was determined, depending on the coating thickness and the thickness of the steel plate. We found that the extreme temperature in a steel plate with a thickness of 0.3 cm is reached at 23, 34, and 46 minutes with a coating thickness of 0.3, 0.45, and 0.6 mm, respectively. Experimental studies of steel plates with thicknesses of 0.5 and 0.8 cm have shown that with an increase in plate thickness at the same values of the thickness of the fire protection coating, the time to reach the extreme temperature increases by about 1 minute. At a coating thickness of 0.8 mm, for steel plates with thicknesses of 0.3 and 0.8 cm, the temperature on the unheated surface of the prototype did not reach the extreme value.Given the results obtained, it will be relevant to solve the inverse problem of thermal conductivity to determine the thermal and physical characteristics of the coating based on numerical data from experimental studies. Keywords: research methodology, standard temperature regime, fire protection coating, steel building structure.

CONDUCTING A NATURAL FIRE TEST IN THE VERTICAL CABLE TUNNEL OF A NUCLEAR POWER PLANT

The article discusses conducting a full-scale fire test in the vertical cable tunnel of a nuclear power plant (NPP). Vertical cable tunnels in NPPs are used for laying cable lines, wires, safety system lines, connecting the equipment room, and the containment of the nuclear power plant block. The paper analyses research methods and selects options that will be effectively used to determine the temperature regime in the vertical cable tunnel of NPPs with known aerodynamic, technical, and geometric parameters and fire loads. The algorithm for conducting full-scale tests in the vertical cable tunnel of an NPP is described. Based on the research, the maximum temperature in the combustion zone is reached on the fourth minute of the full-scale tests in the vertical cable tunnels of nuclear power plants. By obtaining temperature graphs in the vertical cable tunnel of the NPP, it can be observed that the highest temperature is in plane D (800–900 °C), and it depends on the location of the control point. Thermal energy propagates more intensively in the direction opposite to the filling of the space, which is opposite to the exit of combustion products and ventilation openings. The temperature in plane C is in the range of 500–800 °C. Thermal energy propagates most intensively towards the filling to the exit of combustion products. This temperature significantly deviates from the standard temperature regime, which differs greatly from the full-scale experimental study of fires in the vertical cable tunnels of nuclear power plants. It can be concluded that the standard temperature regime of a fire is not adequate for testing the fire resistance of the structural elements of vertical cable tunnels in nuclear power plants. An important conclusion of these studies is the possibility of determining the fire resistance of building structures of vertical cable tunnels of NPPs with the selection of the most severe temperature regime, according to the conducted field test. It means that research results can be used in practice in designing and evaluating the safety of such objects. Keywords: fire, natural fire tests, nuclear power plant, vertical cable tunnel.

Determination of heat transfer process in vertical cable tunnels of nuclear power plants under real fire conditions

The object of the study was heat and mass transfer processes occurring in vertical cable tunnels. The problem to be solved was the definition of process mechanisms in the inner space of the tunnel. For this, field tests were conducted, mathematical models were created, and computational experiments were conducted to establish specific parameters that affect the temperature regime of a fire in a vertical cable tunnel of a nuclear power plant. The dynamics of temperature changes with known geometric parameters and fire load were determined, and the adequacy of mathematical models built in the Fire Dynamics Simulator software was investigated and computational experiments were carried out. It has been proven that they consist in determining the temperature regime in a vertical cable tunnel of a nuclear power plant with known technical and geometric parameters. Such studies have practical applications in the field of safety of nuclear power plants and the development of new technologies in this field. An important conclusion of these studies is the possibility of determining the fire resistance of building structures of vertical cable tunnels of nuclear power plants with the selection of the most severe temperature regime, according to the conducted field test. This means that research results can be used in practice in designing and evaluating the safety of such objects. The conducted research established that the temperature in the inner space of the tunnel can reach values from 1200 to 1400 ℃. The following factors influence the maximum temperature value and the maximum time to reach the maximum temperature in the fire cell: fire load, height and area of the tunnel. With a lower fire load, the maximum temperature in the vertical cable tunnel of the nuclear power plant was 75 % lower. Therefore, the results of these studies have a direct practical application in the field of safety of nuclear power plants and can be used to improve and develop new technologies in this field

Evaluating feasibility of field modeling of fire to calculate fire characteristics in buildings and premises

Introduction. The present paper describes application of a software package using a field model of fire dynamics to calculate fire characteristics in buildings and premises of nuclear power plants (NPP). The authors give necessary justifications for using the software package in performing fire calculations in multifunctional buildings and premises.Aim. To analyze different fire modeling methods, their application and use of the software package for field modeling of fire dynamics to determine the dynamics of fire hazards in complex premises, in facilities with non-uniform fire loads or complex gas exchange processes; to contribute solving the issue of safe distances ensuring that fire cannot spread between equipment elements.Materials and methods. The authors developed and verified a software package to perform calculations using the field model of fire dynamics. The paper presents the basics of the field method for fire modeling in multifunctional premises and the aspects of its application in fire simulation. The presented analytics is substantiated with examples of fire simulation results in real premises of NPPs.Results. Following the analysis of different methods of modeling the dynamics of development and spread of fire hazards, the present paper introduces the possibility of using various methods of fire modeling in the evaluation of fire hazards for buildings and premises. The authors describe the advantages of field modeling method for calculating local parameters of fire. The paper provides information on the software codes to calculate the dynamics of fire and evaluate the thermal effects of fire on building structures.Conclusion. It has been found possible to apply field model of fire dynamics for calculating fire hazards in various buildings, premises and open areas. Calculations using the presented field model enable the sufficiency of fire resistance of building structures and multifunctional premises to be substantiated due to preventing fire spread outside the fire zone during the estimated time of burnout of the total fire load.

Functional assignment of technological accessories for woodworking

Forming a heat and sound insulation board from wood using non-combustible binders can increase the fire protection of the material by forming a protective layer of coke. This will make it possible to develop a new type of fireproof roofing products for building structures. It is not always advisable to treat the surface of a heat and sound insulation board with fireproof coatings, since after prolonged thermal exposure, the combustion stage can be transferred to the interior of the material by smoldering. Therefore, the manufacture of fire-resistant heat- and sound-insulating wood materials, the study of fire protection and the impact of their components on this process is an unresolved component of ensuring the fire resistance of building structures. And, accordingly, they determine the need for such research.
 The paper presents the results of research into the process of protecting wood wool boards with binders based on fire-resistant coatings. Tests on model samples of a wooden board showed that the material based on wood wool and an inorganic binder is characterized by heat absorption and inhibition of oxidation in the gas and condensed phase and the formation of a thermally protective ceramic layer on the surface of the wood. Experimental studies have confirmed that a material based on wood wool and an inorganic binder at a ratio of 1:1 refers to combustible materials, since its smoldering was recorded during exposure to temperature. So, by thermal action for 90 s, the material ignited and the flame spread over the first three zones for 41 s. On the other hand, an increase in the amount of an inorganic-based binder and the use of an organic-mineral binder does not lead to a material fire. In this case, the maximum temperature of the flue gases was about 120 °C, and the flammability index was 0 due to the decomposition of fire retardants under the influence of temperature with the release of incombustible gases, which inhibit the oxidation of the material and significantly increase the formation of a heat-protective layer of coke on the surface of the material. This leads to inhibition of heat transfer of the high-temperature flame to the material. Due to this, it became possible to determine the conditions of fire resistance of the material by forming a barrier for thermal conductivity. The obtained results indicate the possibility of targeted regulation of high temperature transfer processes to organic material by using special binders for wood products.

Моделирование в области обеспечения пожарной безопасности (обзор)

Introduction. To date, there are many (over 150) different mathematical models developed in the field of fire safety. These models are designed to (1) solve problems of heat engineering, heat and mass transfer, human flows, indoor and outdoor fire behaviour, and (2) determine parameters of operation of fire service departments. System research into fire safety models was initiated in the 1970s, and it has been conducted since then. This article presents the results of scientific generalization of mathematical methods of fire safety and provides a brief historical background of the issue. Targets and goals. Scientific generalization of basic mathematical models used to solve research and engineering problems of fire safety. Methods. Methods of systems analysis. Results. The article presents the results of a review of various mathematical models of fire safety. The study encompasses many theories (theories of fire safety of substances and materials, technologies, buildings and structures, fire resistance of building structures and buildings, fire prevention, organization, operation and management of fire service departments, etc.). Principal mathematical methods (analytical and probabilistic ones, as well as simulation), employed by the above theories of fire safety, are considered. Discussion. The authors list more than 150 fire models of different types and classes. Most of them deal with processes of heat and mass transfer during fires, the fire behaviour, the behavior of substances, materials, building structures, etc. on fire. The study also focuses on probabilistic models of the theory of emergency rescue services operation. Conclusions. Currently, a general theory of fire safety is being developed. It is a combination of physicochemical, mathematical, economic-mathematical and other models describing the break-out, development and elimination of fires inside and outside of buildings in case of application of passive and active fire-fighting appliances.

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.

Study of heating of building structures of production facilities to assess their fire resistance

In this article the research of fire resistance limits of structures for industrial facilities has been carried out. It is known that the fire resistance limits of building structures are determined by experimental and computational methods. The research to solve the problem was based on the temperature regime of real fire conditions. The purpose of the study is to assess the fire resistance of building structures of production facilities by calculating heat and mass transfer, taking into account real fire conditions. To achieve the goal we need the following: 1. Investigate the basic fire safety requirements for the building structures of production facilities; 2. Use computational method to substantiate the necessity of increasing the maximum fire-resistance with the help of flame retardants taking into account the worst-case scenario of real fire development. The evaluation of the fire resistance limits of the supporting metal structures showed that these limits are greater than the required R15 in the worst-case scenario of a real fire. To solve this problem, a field calculation method has been applied, which is used for premises of a complex geometric configuration in which one of the geometric dimensions is much larger than the others. The selected calculation method makes it possible to determine the temperature distribution inside the building structure in the one-dimensional case. We consider the worst-case scenario of fire development in terms of heating the supporting metal structures - burning of fuel oil spill in the boiler room. The results of calculations have shown that in the selected scenario of fire development, the maximum temperature of the supporting metal structures within 15 min from the start of the fire is significantly less than the critical temperature of 500°C. Fire protection coatings for the treatment of load-bearing structures of the production facility are not required.

TO THE ISSUE OF THE FLAMMABILITY REDUCING AND THE FIRE RESISTANCE INCREASING OF METAL STRUCTURES

Problem statement. Based on the fire safety concept in the state program of Ukraine, the issue of flammability reducing for materials and fire resistance increasing for structures is selected as one of the priority scientific areas in fundamental and applied research. It provides for the implementation of works aimed at ensuring fire protection, the development of fire protection products that reduce the flammability of materials and increase the fire resistance of building structures, the development and improvement of methods for determining the fire hazard of materials. The purpose of the article. Increasing the fire resistance of metal structures due to the use of fire-resistant intumescent coatings, developing new approaches, criteria and methods for assessing fire resistance and increasing the fire resistance of modern metal structures. Conclusions. As a result of the analytical studies, mathematical models were obtained that allow predicting the fire resistance and increasing the fire resistance for metal structures depending on the thickness of the coating, the given thickness of the metal and the type of fire retardant composition. An engineering methodology for assessing fire resistance and increasing the fire resistance of steel structures was developed.

Analyzing the influence of the fire resistance of building structures on human safety in case of a fire

Introduction. Methodological provisions must be developed to evaluate the impact of the fire resistance factor of building structures on human safety during evacuation and rescue with account taken of the composition andfunctional characteristics of other fire safety systems to formulate modern regulatory requirements for the fire resistance of building structures under fire conditions, develop science-based solutions for the fire safety of buildings and structures in case of forced deviations from the fire resistance requirements set in regulatory documents, and justify the construction of buildings and structures, based on modern structural systems, having non-standard fire resistance limits, etc.The purpose of the article is to develop general methodological provisions and mathematical relationships that allow evaluating the impact of the fire resistance limits of building structures both on safe evacuation and safe rescue from buildings.Methods. Analytical and mathematical methods are used to evaluate the combined effect of changes in the fire hazard arising along the evacuation routes, in a room with a person waiting to be rescued by fire departments, as well as along the routes taken by fire departments carrying this person out, in combination with the evaluated time span needed for the structure to lose its fire resistance. The value of this time span is used to identify the time available for the safe evacuation and rescue of people.Results. Theoretical provisions have been developed to take into account the influence of the fire resistance factor of building constructions on the safety of people in a building in case of a fire.Conclusions. The research findings were contributed to the general methodological provisions and mathematical relationships needed to determine the quantitative relationships between the extent of fire resistance of a building, fire resistance limits of building structures, the time of arrival of fire departments, types of fire alarm and evacuation control systems, and the possibility of safe evacuation and rescue of people from a building.

Оцінювання вогнестійкості вогнезахищених сталевих балок

Purpose. Development of a computer model for the study of fire resistance of steel structures protected by fire-resistant coatings, using the example of a fire-resistant steel beam created in the LIRA-SAPR software complex (Ukraine). Methods. Finite element method, application of computational methods of numerical modelling of the LIRA-SAPR software complex, mathematical modelling of thermal processes of non-stationary thermal conductivity. Results. A computer model was developed in the LIRA- SAPR software complex, with the help of which thermal engineering calculation of the beam was carried out. The model makes it possible to evaluate the fire resistance of both unprotected and fire-protected steel beams, to take into account the properties of the beam material and the material of the fire-resistant coating. The peculiarity of modelling the non-stationary heating of a fire-resistant steel beam is to specify the thermophysical characteristics of the fire-resistant coating when solving the problem of non-stationary thermal conductivity. The results of the calculated determination of the fire resistance of the fire-resistant steel beam were compared with experimental data. As a result, a satisfactory convergence of the results of the calculation and experimental study of fire resistance was established (the error is no more than 12%). The results of the experimental determination of the fire resistance of unloaded beams under fire conditions of the standard fire temperature regime were analysed. The accuracy of the developed computer model was evaluated with the results of the experiment. Scientific novelty. A finite-element model of a fire-resistant steel beam has been developed in the LIRA- SAPR software complex, which allows calculating the fire resistance limits of beams protected by fire-resistant coatings with scientifically justified parameters with sufficient accuracy for engineering calculations. Practical significance. It consists in creating the basis for the calculated assessment of fire resistance of building structures protected by fire-resistant coatings by creating computer models capable of performing fire resistance calculations. Due to this, there should be a significant reduction in the cost of work on fire resistance assessment and, as a result, an increase in the effectiveness of measures to increase the fire resistance of building structures.

A comparative analysis of the requirements of Russia and the United States to the fire resistance of building structures of oil refineries and petrochemical plants

Introduction. Currently, national standards and codes of practice contain deterministic values of the fire resistance of building structures of facilities of the Russian fuel and energy complex (FEC), while a probabilistic approach to determining their fire resistance is not specified in the Russian regulatory documents. The methodology of the probabilistic approach to the fire resistance of structures is detailed in API 2218 “Fireproofing Practices in Petroleum and Petrochemical Processing Plants”, developed by the American Petroleum Institute.Methods. A comparative analysis of the Russian regulatory documents on fire safety and API 2218 in terms of the established concepts of fireproofing and requirements for the fire resistance limits of building structures of oil and gas industry facilities, is carried out.Results. It was established that the Russian Federation has no regulatory documents establishing methods based on the probabilistic approach, including determination of the required fire resistance limits and points of application of fire-resistant coatings at facilities of the fuel and energy complex by analogy with international standard API 2218.Conclusion. Based on the analysis, it was concluded that approaches to the philosophy of the fire resistance of structures of buildings and structures of the fuel and energy complex in the documents under consideration are fundamentally different. In order to improve the Russian regulatory and technical framework, governing fire safety and fire resistance, it is proposed to consider the requirements of foreign documents that take into account proven international engineering and technical practices, in particular, the use of a probabilistic approach taking into account hydrocarbon fires.

Огнезащита стальных и железобетонных конструкций производственных зданий и сооружений

Variants of progressive solutions for the use of efficient fire protection means for steel and reinforced concrete structures of the industrial buildings and structures are considered for the purpose of increasing the actual fire resistance and ensuring the requirements of fire safety norms. Distinctive features of the temperature regimes in the initial phase of a real fire from a standard fire were established when assessing the fire resistance of building structures. It is proposed to use such standardized temperature regimes of fire for assessing the fire resistance of building structures, as standard — in the industrial buildings; temperature regime of hydrocarbons combustion — for oil and gas, petrochemical enterprises, offshore stationary platforms; tunnel temperature regime — in the road and railway tunnels. Considering the operating conditions and performance of work on fire protection, the degree of aggressiveness of the environment, the structural and methodological scheme was developed for selecting passive fire protection for steel structures. Recommendations are given on limiting the use of intumescent paints for load-bearing steel structures involved in the overall stability of buildings, with the required fire resistance limit of no more than 30 minutes. To calculate the temperature over the section of the structure during its heating, the dependences of the change in the coefficients of thermal conductivity and heat capacity of fire-retardant linings under fire were obtained. Experimental studies were conducted related to the fire resistance of reinforced concrete floor slabs and slabs with an external reinforcement system based on the carbon composite material with various types of fire-retardant materials. The issue of protecting the lining blocks of road and railway tunnels from brittle (explosive) destruction of concrete in a fire is considered. It is experimentally confirmed that the addition of polypropylene fibers to the concrete mixture replaces the use of fire protection for the tunnels enclosing structures.

Investigation of the influence of the configuration of the fire furnace chamber on the temperature regime during the implementation of tests for fire resistance

The issue related to the conditions for creating the required temperature regime of fire when testing structures for fire resistance has not been studied in detail up to now. That necessitated determining the technical conditions under which it is possible to comply with the standard temperature regime of fire in the fire chamber of the furnace. The influence of the design parameters of the fire furnace chamber on the condition of compliance with the standard fire temperature regime when tested for fire resistance has been established. One of the most effective methods for examining such an impact is computer simulation. A computer model of the fire furnace was built on the basis of a comprehensive analysis and earlier work on the study of such furnaces, taking into consideration technical characteristics, in particular, geometrical parameters, fuel and air supply systems. The obtained research results are a prerequisite for scientific substantiation of the design parameters of fire furnaces and their engineering systems, which is necessary to comply with the standard temperature regime of fire in the furnace fire chamber. This makes it possible to provide the necessary conditions for testing building structures for fire resistance in compliance with the requirements of the relevant standards. The computer model constructed makes it possible to create the necessary temperature regime in the fire chamber of the furnace (in this study, the standard temperature of fire). As a result of the study, the technical parameters of the fuel supply and ventilation system were determined, which ensure compliance with the standard temperature regime in the fire chamber of the furnace. That makes it possible to build an automated complex of the testing process for fire resistance of building structures. In addition, the data obtained can be the basis for the design of such fire furnaces with the ability to comply with different fire temperature regimes without the intervention of the operator.

Концепция расчетного определения фактического предела огнестойкости строительных конструкций

Проведен краткий анализ понятий, связанных с расчетом пределов огнестойкости строительных конструкций. Дано определение термина «фактический предел огнестойкости», которое отсутствует в нормативных документах по пожарной безопасности. Отмечено, что это связано с использованием на практике значений пределов огнестойкости, определенных для стандартных температурных режимов пожара, в то время как на практике указанные температурные режимы, как правило, отличаются от стандартных. Предложена концепция определения фактического предела огнестойкости, основанная на моделировании воздействия на строительную конструкцию температурного режима реального пожара (например, с помощью программного комплекса FDS 6). The brief analysis of definitions connected with estimation of fire resistance limits of building structures is conducted. There is given the determination of term “actual fire resistance limit” that is absent in fire safety normative documents. It is caused by practical application of the fire resistance limits determined for standard temperature regimes of fires only, but at the same time the temperature regimes of real fires as a rule differ from the standard regimes. There is proposed the method for determination of the actual fire resistance limit based on the modeling of influence of the real fire temperature regime on buildings structures. This modeling can be made by an application of CFD methods (for example, with the help of FDS 6 software complex). The required reliability of the building structure is considered. The proposed method can solve the problem of practical applicability of certain structural unit during designing buildings and structures, for which the use of the resistance limits obtained for the standard fire temperature regimes can lead to unjustified economic expenditures without an appropriate elevation of fire safety level of the object.

Оценка огнезащитной эффективности покрытий для стальных конструкций

Представлены результаты анализа экспериментальной и аналитической оценки огнезащитной эффективности покрытий для стальных конструкций. Обобщены данные многолетних исследований по определению зависимостей от температуры таких теплофизических характеристик, как теплопроводность и теплоемкость. Разработана структурно-методологическая схема выбора огнезащитных покрытий для стальных конструкций в целях обеспечения нормативных требований по огнестойкости. Проведены экспериментальные исследования по определению огнезащитной эффективности терморасширяющихся покрытий на эпоксидной основе при воздействии температурного режима горения углеводородов. Рассмотрен вопрос о гармонизации методики экспериментальной оценки огнезащитной эффективности средств огнезащиты для стальных конструкций с действующими европейскими нормами. Установлены критерии выбора пассивной огнезащиты, зависящие от области применения способов огнезащиты. Steel structures have high strength, relative lightness and durability, but when exposed to high temperatures in a fire, they deform, lose stability and load-bearing capacity. The collapse of load-bearing steel structures can occur in 10-15 minutes after the fire start. The actual fire resistance limit of structures can be increased by using the active and passive fire protection systems. The use of the active system for increasing the actual fire resistance limit is not provided in the regulatory documents. Passive fire protection is a complex of technical solutions including the use of non-flammable materials and bulging compounds. It is also an integral part of the building structure that ensures the required fire resistance limit. Assessment of fire resistance of building structures of residential, public, warehouse and industrial buildings is carried out taking into account the temperature regime (cellulose) of a standard fire. At oil and gas, petrochemical enterprises as well as at oil production platforms fires can occur at combustion of various hydrocarbon fuels which are characterized by a rapid temperature increase to 1100 °C. In this case, in accordance with GOST R EN 1363-2-2014, the temperature regime of hydrocarbon combustion is used to assess the fire resistance of building structures. The fire-retardant effectiveness of fire protection means for steel structures is determined by the heating time of the standard I-shaped column without applying a static load on the sample to the average “critical” temperature of the steel of 500 °C. Materials used for fire protection of steel structures must have a good thermal insulation ability, which is estimated by the coefficient of thermal conductivity. When heated to high temperatures, the thermal conductivity coefficient of fire-resistant materials varies depending on their composition and temperature. Based on the analysis of research to determine the fire-retardant effectiveness of fire protection means for steel structures there was developed a structural and methodological scheme that allows to make a choice of fire protection. Currently, as a fire protection there are widely used intumescent paints and thermo-expandable coatings. Taking into account the lack of knowledge of the influence of long-term operation and a large number of other technological factors on the fire-retardant effectiveness of coatings of steel structures covered with intumescent paints, it would be right to limit the use of such type of fire protection for load-bearing structures contributing to the overall sustainability of buildings with a required fire resistance of R 30. For fire protection of steel structures of oil and gas facilities located in the open air, in severe climatic conditions and exposed to aggressive environments there is successfully used a thermo-expandable two-component epoxy-based coating. The analysis of experimental data showed that the use of epoxy-based coatings is suitable for metal structures in the open air. In closed rooms the epoxy intumescent coating should not be used because at high temperature in a fire it ignites with toxic combustion products release.

Overview of software designated for the analysis of fire resistance of building structures exposed to various fire models

Introduction. When analyzing the fire safety of a facility, the conformity of actual limits of fire resistance of structures to the requirements of statutory documents is checked. Due to the complexity of the equations describing real systems and an extensive number of iterations required to obtain accurate results, software is used to perform calculations. One of the main goals of the paper is to analyze the software designated for the analysis of the fire resistance of building structures in case of different fire models. The paper presents an analysis of the criteria for the evaluation of software programs and their classification, evaluation of recommendations for choosing fire safety software in compliance with the specific requirements of users.Main (analytical) part. The paper analyzes various models of fires, taking into account the stages of fire spread, thermal and mechanical effects on structures exposed to fire, and prerequisites for their use by the software designated for the analysis of the fire resistance of building structures. Fire resistance models of structures, zone and field models, as well as models used to calculate evacuation time and detector response time when solving related problems are considered. The classification of software programmes is analyzed subject to the type of problems to be solved: the behavior of a structure exposed to high temperatures and mechanical impacts in case of real fire, and requirements applicable to safe structures. Certain estimates and assumptions, necessary for specialists to use software in their calculations, are considered.Conclusions. Recommendations on the choice of fire safety assurance software, meeting the specific needs of users, are provided.

How does concrete strength affect the fire resistance?

PurposeThe aim of the research was to investigate the effect of concrete strength on the fire resistance of structures. At first, it may seem contradictory that higher concrete strengths can decrease the fire resistance of building structures. However, if the strength of the concrete exceeds a maximum value, the risk of spalling (the detachment of the concrete surface) significantly.Design/methodology/approachPrefabricated structural elements are often produced with higher strength. The higher concrete strengths generally do not cause a reduction in the load bearing capacity, but it can have serious consequences in case of structural fire design. Results of two prefabricated elements, namely, one slab (TT shaped panel) and one single layer wall panel, were examined. Results of the specimen with the originally designed composition and a specimen with modified concrete composition were examined, were polymer fibres were added to prevent spalling.FindingsAs a result of the experiments, more strict regulations in the standards the author is suggested including more strict regulations in the standards. It has been proved that to ensure the fire safety of the reinforced concrete structures, it is required after polymer fibres even in lower concrete strength class than prescribed by the standard. In addition, during the classification and evaluation of structures, it is advisable to introduce an upper limit of allowed concrete strength for fire safety reasons.Originality/valueAs a result of the experiments, the author suggests including more strict regulations in the standards. It has been proved that to ensure the fire safety of the reinforced concrete structures, it is necessary to require the addition of polymer fibres even in lower concrete strength class than prescribed by the standard. In addition, during the classification and evaluation of structures, it is advisable to introduce an upper limit of allowed concrete strength for fire safety reasons.