Fire Resistance Of Buildings Research Articles

THEORETICAL ANALYSIS OF THE COMBUSTION PROCESS

Problem statement. The analysis of fire hazard shows that fires cause significant material damage to the economy around the world, significantly complicating the environmental situation, endangering human life. Thus, in Ukraine there are more than 50 thousand fires every year, in which people die, and material damage exceeds hundreds of millions of hryvnias, incidental losses are 20 times greater. This alarming statistics is largely due to the increased fire hazard of buildings and structures erected and operated by changing production technology, increasing the number of storeys and building density, changing traditional and material-intensive technologies of building new advanced technologies with effective building materials from wood, plastics and polymers, metal, etc. Many of these materials are highly sensitive to high temperatures and fire. Thus, wooden and plastic building materials and structures under the action of high temperatures can burn, releasing significant amounts of heat and toxic substances. Metal structures under fire are rapidly heated to critical temperatures, which leads to a loss of their load-bearing capacity. The purpose of the article. Research of regularities at high-temperature heating of wood and metal, at burning and decomposition of wood. Conclusions. Fire protection of building structures is a necessary part of preventive measures aimed at ensuring fire safety and fire resistance of buildings and structures. The main task of structures’ fire protection is to reduce the flammability of materials and reduce heat transfer to them.

Расчетно-аналитическое обоснование предельных значений массы аммиачной селитры при хранении на складах и терминалах

On the basis of theory of stationary thermal explosion of A.D. Frank-Kamenetsky, depending on the temperature of the critical size of the ammonium nitrate embankment, the calculations were performed, which show that it can be stored in the large volumes at the temperatures up to 30 °C. On the contrary, at the temperatures above 100 °C (for example, at 200 °C), the decomposition of nitrate occurs with acceleration and can lead to an explosion. Based on the studies performed, it is shown that the changes and additions to the fire safety requirements for ammonium nitrate storage in the buildings and structures should be determined by the requirements for fire resistance of buildings (at least II degree of fire resistance), for the purity of the product and its packaging, for the exclusion of contacts with organic substances and materials, storage conditions. Additional fire safety requirements were developed for inclusion in the normative document regarding ammonium nitrate storage. Ammonium nitrate is allowed to be stored in one-story warehouse buildings of at least II degree of fire resistance, structural fire hazard class C0. The floor area within the fire compartment should not exceed 10 500 m2. Between the fire-fighting walls of the 1st type, it is allowed to store no more than 25 000 tons of nitrite in bulk or in the special bags, as well as in the soft specialized containers for bulk products in accordance with GOST 2—2013.The conditions for placing ammonium nitrate in the stacks should be accepted in accordance with the requirements of SP 92.13330.2012. Temperature in the storage room of ammonium nitrate should not exceed 30 °C with a relative humidity of not more than 60 %. Warehouses for storing ammonium nitrate should be equipped with general exchange supply and exhaust and (or) emergency ventilation, in order to exclude the formation of a fire and explosion hazardous environment in the room during the decomposition of ammonium nitrate. Warehouses for storing ammonium nitrate in an amount of not more than 5 thousand tons may be separated from other premises, including from the warehouses for fertilizers and pesticides, by solid (without openings) type 2 fire walls.

Оценка безопасных противопожарных расстояний от лесных насаждений до зданий и сооружений

Проанализированы нормативные требования к противопожарным разрывам от зданий и сооружений до границ лесных насаждений. Рассмотрены особенности лесных пожаров с точки зрения нормирования противопожарных расстояний между объектами защиты. Изучена возможность применения действующих нормативных методов расчета противопожарных разрывов между объектами защиты для определения противопожарных расстояний от зданий и сооружений до лесных насаждений, а также разработаны и обоснованы необходимые рекомендации. Рассмотрен пример расчета для здания, расположенного вблизи леса. The requirements for fire breaks in the Russian Federation are regulated by the regulatory requirements for fire safety. Most of the calculated methods of fire breaks between the objects of protection are based on the value determination of the heat flow transmitted from fire at one of the objects to the combustible materials of the neighbor object. The possibility of calculating the values of fire breaks between buildings and structures is provided in the «Methodology for calculating fire breaks between buildings and structures» (Appendix A of the set of rules SP 4.13130.2013). There are no regulatory requirements for calculating fire distances from forest area to buildings and structures. The relevance of such requirements is due to the development of mass construction in the territories located in the zones of possible spread of forest and other landscape fires. The analysis of the regulatory requirements for fire breaks from buildings and structures to the boundaries of forest area showed that the basic principles for justifying the values of fire distances are related to the types of forest area and the characteristics of the buildings and structures of settlements (fire resistance of buildings, fire hazard of structural elements, etc.). Calculations of fire breaks from forest area to buildings and structures have special features so, when choosing a fire scenario, the main mechanisms of heat transfer, the type of forest vegetation and the type of fire - riding, grassroots or underground - must be taken into account. To apply the provisions of the «Methodology for calculating fire-fighting gaps between buildings and structures» (Annex A of the Set of Rules SP 4.13130.2013) for assessment of fire distances from buildings and structures to the forest area there was developed a set of recommendations and there was given an example of calculation on a specific object. At the same time, the most unfavourable fire scenarios were selected. The calculated dependences of the heat radiation intensity on the distance in case of fire in a residential building and at a forest fire are obtained. Based on the calculation results there were determined the necessary initial data for the development of compensating fire-fighting measures to eliminate the possibility of forest fire spreading to the buildings and structures of the object.

Study of intumescent coatings in operation using x-ray phase and thermal analysis and IR spectroscopy

The problem of increasing the fire resistance of buildings and structures is still relevant. Nowadays, fireproof intumescent and other materials with a limited service life are used to ensure fire safety of infrastructure and social facilities. Among these, fire-proofing of metal structures is one of the vital problems. The results of studying samples of fire-retardant intumescent coatings based on ammonium polyphosphate-melamine-pentaerythritol and subjected to artificial climatic aging (3, 6, and 9 years) and thermal exposure (heating to 300 and 500°C) are presented. The methods of X-ray diffraction and thermal analyzes, optical and IR spectroscopy are used to study the phase and structural composition of materials. It was found that the intumescence of the samples significantly decreases during service life of the coating. This leads to a decrease in the fire resistance of the protected object. Moreover, a sharp change in the phase composition of materials occurs as a result of aging and heating, accompanied by a decrease in the degree of crystallinity. Since the composition of fire-retardant coatings plays a key role in ensuring the fire safety of buildings and structures, the results of the study can be used for timely detection of violations in the quality of coatings and forecasting their service life.

Fire resistant properties of construction structure

This article discusses the fire resistance problems of building structures, their criteria for use, the temporal limits of the spread of fire in buildings and building structures, and their classification. A calculation method is proposed for determining the properties of heat-resistant concrete and building materials, the grouping of building materials by fire resistance, the level of fire resistance of buildings and structures, as well as the determination of the fire-resistant properties of buildings by a fire test. The question of the use of heat-resistant heavy concrete with their properties is considered.

Improved Calculation Method for Insulation-based Fire Resistance of Composite Slabs

Abstract Floor slabs play a critical role in the fire resistance of buildings, not only by maintaining structural stability and integrity, but also by providing thermal insulation to limit the rise in temperature of floors above a fire. Composite slabs, consisting of concrete topping on steel decking, are common in steel building construction, but the profiled geometry of the decking makes the analysis of heat transfer in composite slabs more complex than for flat slabs. A method for calculating the insulation-based fire resistance of composite slabs with profiled steel decking is provided in Annex D of Eurocode 4 (EC4). However, the applicability of the EC4 calculation method is limited to a range of commonly used slab geometries from the 1990s, which is narrower than the range used in current practice. In addition, the EC4 calculation method assumes a specific value of moisture content for the concrete, and different values of moisture content can significantly affect the fire resistance, as shown in this study. This paper proposes an improved algebraic expression for estimation of the insulation-based fire resistance of composite slabs that explicitly accounts for moisture content and is applicable to an extended range of slab geometries. The proposed expression is developed based on computed values of fire resistance obtained from a validated finite element modeling approach. A set of 54 composite slab configurations are selected for analysis using a sequential experimental design. The accuracy of the proposed method is verified against numerical results for an additional set of 32 slab configurations and is also validated against experimental data. Comparisons of the proposed calculation method with the results of the verification analyses show deviations of less than 15 min in all cases for the insulation-based fire resistance of the composite slabs.

Improved calculation method for insulation-based fire resistance of composite slabs

Floor slabs play a critical role in the fire resistance of buildings, not only by maintaining structural stability and integrity, but also by providing thermal insulation to limit the rise in temperature of floors above a fire. Composite slabs, consisting of concrete topping on steel decking, are common in steel building construction, but the profiled geometry of the decking makes the analysis of heat transfer in composite slabs more complex than for flat slabs. A method for calculating the insulation-based fire resistance of composite slabs with profiled steel decking is provided in Annex D of Eurocode 4 (EC4). However, the applicability of the EC4 calculation method is limited to a range of commonly used slab geometries from the 1990s, which is narrower than the range used in current practice. In addition, the EC4 calculation method assumes a specific value of moisture content for the concrete, and different values of moisture content can significantly affect the fire resistance, as shown in this study. This paper proposes an improved algebraic expression for estimation of the insulation-based fire resistance of composite slabs that explicitly accounts for moisture content and is applicable to an extended range of slab geometries. The proposed expression is developed based on computed values of fire resistance obtained from a validated finite element modeling approach. A set of 54 composite slab configurations are selected for analysis using a sequential experimental design. The accuracy of the proposed method is verified against numerical results for an additional set of 32 slab configurations and is also validated against experimental data. Comparisons of the proposed calculation method with the results of the verification analyses show deviations of less than 15 min in all cases for the insulation-based fire resistance of the composite slabs.

Influence of the Maximum Aggregate Grain Size on the Modulus of Elasticity and on the Parameters of the Acoustic Emission of Concrete Exposed to High Temperatures

Several very large and tragic fires of buildings have occurred recently, drawing attention to the issues of fire resistance of buildings (especially high-rise buildings and tunnels) and of building materials. For cement-based composites, it is essential to comprehensively understand the behaviour of their internal structures when exposed to high temperatures. This paper deals with the changes of the physical properties of concrete with different aggregate grain sizes when exposed to high temperatures. The emphasis is placed on the changes of the static and dynamic modulus of elasticity as an important parameter in assessing the behaviour of structures or their parts. During the test of the static modulus of elasticity, the acoustic emission method was also used as its results may reveal the behaviour of the internal structure of the material during mechanical loading.

COUPLED SIMULATION FOR FIRE-EXPOSED STRUCTURES USING CFD AND THERMO-MECHANICAL MODELS

Fire resistance of buildings is based on fire tests in furnaces with gas burners. However, the tests are very expensive and time consuming. This article presents a coupled simulation of an element loaded by a force and a fire loading. The simulation solves a weakly-coupled problem, consisting of fluid dynamics, heat transfer and mechanical model. The temperature field from the computational fluid dynamics simulation (CFD) creates Cauchy and radiative boundary conditions for the thermal model. Then, the temperature field from element is passed to the mechanical model, which induces thermal strain and modifies material parameters. The fluid dynamics is computed with Fire Dynamics Simulator and the thermo-mechanical task is solved in OOFEM. Both softwares are interconnected with MuPIF python library, which allows smooth data transfer across the different meshes, orchestrating simulations in particular codes, exporting results to the VTK formats and distributed computing.

RELIABILITY OF TIMBER STRUCTURES EXPOSED TO FIRE

<p>Until recently, the fire resistance of buildings was based on the ISO standard curve. ISO standard curve used by the current norm is too simple, unrealistic and lead to uneconomic situations with no guarantee of security proportional to the invested money. Unlike the fire design of the steel, concrete or composite structures, methods for fire design of timber structures have been greatly simplified. Generally, it is not necessary to check the reduction of strength in the residual section because each increase of temperature is considered small and it is ignored. Global fire safety concept of timber structures is presented according to the recommendations from Eurocode norms. Special attention was given to natural fire design with two different methods of parametric exposure which are given in EN1995-1-2.</p>This paper presents reliability analysis of a glulam beam in a case of fire. The limit-state functions for maximum bending stress of glulam beam in fire conditions are formed. Reliability indexes are obtained from the limit state of the beam exposed to 30 min fire. Reliability index in the Eurocodes (reliability class RC2) compared to the calculated reliability indexes obtained by the methods of reduced strength and effective section were described.

철골 철근콘크리트 보 및 철골철망 모르타르조 보의 전열특성 및 화재거동에 관한 실험적 연구

본 연구에서는 건축물의 피난 및 방화에 관한 규칙 제3조에 명시된 법정내화구조 중 보의 내화성능을 평가하고, 국내외 규정과 비교 및 분석을 하였다. 현행 규칙에 따르면 국내의 법정내화구조는 피난 및 방화구조에 관한 규칙의 시방기준을 만족하면 최대 3시간의 내화성능을 갖는 것으로 본다. 법정내화구조로서 보는 총 5개의 구조가 있으나, 본 연구에서는 우선 철근콘크리조를 대상으로 피복두께에 따른 내화성능을 평가하였다. 실험결과 하중비 0.5와 피복두께 40 mm를 확보할 경우, 최대 법정요구내화시간인 3시간을 만족하는 것으로 나타났다. 철골철망 모르타르조 보의 경우, 피복두께 60 mm 하중비 0.4에서 3시간 내화성능을 확보할 수 있다. This study evaluates the fire resisting capacity of the beam of the legal fire resistance construction, which establishes the Article 3 of the Regulations on Escape and Fire Resistance of Buildings. There are a total of five structures that we consider as legal fire resistance constructions, however, this study has a primary target of the reinforced concrete beam, and tests the fire-resistant performance depend on the covering depth of reinforce concrete. The results showed that it meets the three hours, the maximum statutory fire resistance time, if it was a load ratio of 0.5 and covering depth of 40 cm. Steel framed mortar beam is legal fire resistance structure that it was possessed three hours fire resistance performance, if it was a load ratio of 0.4 and covering depth of 60 mm.

The Practical Application of Structural Fire Engineering on a Retail Development in the UK

The British Building Regulations allow the application of performance based design methods to ensure the fire resistance of buildings. This has led to significant amounts of research and testing on the fire performance of structures. This research generated the understanding that steel framed buildings have an inherent fire resistance, which has in turn resulted in the development of specialist numerical calculation tools as well as simplified design methods for the fire design of steel-framed structures. The paper describes the practical application of these structural fire engineering methods using a large retail and cinema complex in the UK as a case study. The finite element software Vulcan has been used to analyse the behaviour of large parts of this multi-storey building during a number of likely design fire scenarios in order to optimise the amount of applied passive fire protection to the structure. The building is constructed as a steel composite structure with normal down-stand composite beams supporting a composite floor on trapezoidal metal deck. This type of structure is ideal to utilise the benefits of tensile membrane action during a fire which can be used to omit fire protection from off grid secondary beams. Due to the size and the multiple usage and changing floor construction of the buildings five different sub-frames haven been analysed. In the UK a number of simplified methods are currently applied to justify partially protected steel structures. These methods are based on individual bays only and therefore do not consider the effects of the surrounding structure. In order to investigate the differences further, the behaviour of the large sub-frame models has been compared with the results of individual bay analysis methods.

Editorial[Buildings` Behaviour in Fire

Fire causes a significant loss to life and property, this is why the fire resistance of buildings is one of the main considerations for structural designers. The behaviour of structures exposed to fire is usually described in terms of the concept of fire resistance, which is the period of time under exposure to a standard fire time-temperature curve at which some prescribed form of limiting behaviour occurs. In performance-based design, this limiting behaviour may be defined either as a real structural collapse or as a failure of integrity, which would allow fire spread to occur but is more usually defined in terms of a deflection limit. The recent design codes, such as Eurocodes, have taken a step toward full performance-based design by allowing designers to treat fire as one of the basic design limit states, taking account of: (1) non-uniform heating due to partial protection, which may be inherent in the framing system or specially applied, (2) the level of loading at the fire limit state, using partial safety factors lower than those used for ultimate limit states because of the relative improbability of such accidental combinations, and (3) realistic stress-strain characteristics of structural materials at elevated temperatures. The main limitation of these codified approaches is that they are based on the behaviour under test of isolated simply supported members, usually heated according to the standard ISO834 time-temperature curve. In real buildings, the structural elements form part of a continuous assembly and building fires often remain localized, with the fire-affected region of the structure being subjected to significant restraint from the cooler areas surrounding it. The real behaviour of these structural elements can therefore be very different from that indicated by the standard furnace tests.

Building Fire Safety, Structural Fire Tests, and Performance Based Codes

Building fire safety is a general term covering life safety of occupants and fire resistance of buildings. The former deals with emergency exits, escape signs, detecting system, alarms, sprinklers, smoke control, and fire extinguishers. The later involves with construction materials, architectural design to prevent fire spread, and theoretical analysis as well as experimental study to maximize structural performance in fire. Among them the experimental study, particularly structural fire tests, has attracted serious attentions from international engineering societies. The first ISO TC-92 meeting held in London, 1961 entitled, “Fire Tests on Building Materials and Structures” set a landmark of fire resistance research. Since then, innovative technologies on building materials, engineering analyses, structural designs, and fire tests have been developed to generate fire ratings of steel and concrete elements. Of these developments, an element fire test is the most expensive attributed to a need a large furnace equipped with sophisticated hydraulic system, temperature control and data acquisition units. The obtained data have been widely used by engineers, insurers, and building officials in assessing fire safety of buildings. Fire tests of full sized concrete beams, slabs, and columns in North America were carried out in accordance with the ASTM E-119 standard procedure or ISO 834. One of the standard’s weaknesses involves with a provision allowing the supported regions of a specimen be protected from fire exposures. The fire endurance of a structural element tested without exposing its end points to fire conceivably differs from that of a correspondent member of an actual building in fire. An idea to include structural joints in a fire test surfaced 4 decades ago but did not receive public attention until PBC was introduced in early 1980’s. The uniqueness of PBC includes design flexibility and requiring verification tests of frame structures. The 911 WTC disaster investigation conducted by National Institute of Standards and Technology (NIST) supports PBC requirements on frame fire tests.

Fire Resistance of Buildings

Fire Resistance of Buildings