Fire Safety Engineering Design Research Articles

Numerical and Experimental Investigation on the Effect of Mechanical Smoke Extraction Caused by External Wind in Subway Station Halls

When fires break out in subway station halls, traditional smoke extraction (TSE) systems are employed with the aim of preventing smoke from spreading to the platform and passageways. The functionality of TSE systems under the influence of external winds needs to be further explored. Based on a numerical method, this study investigated the effect on TSE systems under the influence of external wind. A numerical model was established and validated by means of full-scale field tests to ensure accuracy. Subsequently, the validated model was applied to study the effect of the external wind directions and speeds on the smoke diffusion distance. The results showed that when all entrances and exits were on the windward side, the external wind direction led to serious longitudinal diffusion of the smoke toward the side with fewer entrances and exits of the station hall, and the diffusion distance increased with increasing wind speed. The diffusion distance reached a maximum value of 61.32 m when the outdoor wind was 5 m/s, which was 67.9% higher than that under no wind. When all the entrances and exits were on the leeward side, the external wind had little influence on the degree of smoke spread, with the greatest smoke diffusion distance being only 4.76% longer than that under no wind. When two entrances and exits were on the windward side and the other on the leeward side, the external wind caused smoke to spread to a passageway, and the degree of smoke spread was more unfavorable at higher wind speeds, with the longest diffusion distance being 7.28 m. To prevent smoke from spreading to passageways and to effectively shorten the longitudinal diffusion distance of smoke, an optimized smoke control (OSC) system was proposed, employing center and passageway smoke barriers, which were able to shorten the diffusion distances by 35.45%, 13.64%, and 2.35%. In particular, smoke diffusion did not occur in passageways. This study provides a reference for the fire safety engineering design of subway stations.

Research on thermal-driven smoke control by using smoke curtains during a subway platform fire

During the occurrence of a fire on a subway platform, the focus is usually on controlling the ventilation and smoke exhaust systems to prevent smoke from spreading from the platform floor to the lobby floor. The passive method of using smoke curtains to control the smoke needs to be further explored. This study aims to predict the optimal smoke curtain depth required to prevent the spreading of the smoke from the platform floor to the lobby floor. A full-scale experiment was conducted, the results of which verified the computational application used. Furthermore, by combining theoretical analysis, more numerical calculations were conducted to further analyze the effect of the heat release rate (HRR) of fire (Q) and smoke exhaust volume (Ve) on smoke layer thickness (smoke curtain depth (hsc)) under the ceiling of the platform area. The expressions of minimum smoke curtain depth as a function of HRR and smoke exhaust volume were determined through the numerical results based on different plume models (e.g., Zukoski plume, Heskestad plume, etc.). By using the smoke curtain to control smoke, this method reduces the operating cost of the ventilation system. The findings of this study can provide a reference for the fire-safety engineering design of subway stations.

National fire regulations for the use of wood in buildings – worldwide review 2020

ABSTRACT The possibilities for building in wood have gradually increased in recent decades mainly due to environmental benefits. But there are still restrictions in terms of fire regulations in many countries, especially for taller buildings. The situation has therefore been mapped in about 40 countries on four continents as an update to a survey in 2002. The main issues are how high buildings with load-bearing wooden frames may be built and how much visible wood may be used both inside and outside on facades. The restrictions apply primarily to prescriptive fire design according to simplified design with detailed rules, which are mainly used for residential buildings and offices. For more complicated constructions e.g. public buildings, shopping centers, arenas and assembly halls, performance based design can be used by fire safety engineering design using, e.g. methods for evacuation and smoke filling, which increases the possibilities of using wood in buildings. The possibilities to use wood in buildings increase if sprinklers are installed, which is highlighted. Major differences between countries have been identified, both in terms of the number of storeys permitted in wood structures, and of the amounts of visible wood surfaces in interior and exterior applications. Several countries have no specific regulations, or do not limit the number of storeys in wooden buildings. The conclusion is that the differences are still large and that many countries have not yet started to use larger wood constructions despite supplies of forest resources, but harmonizing activities on performance based principles are ongoing worldwide.

Defining ALARP for fire safety engineering design via the Life Quality Index

Fire safety engineering designs should comply with the ALARP requirement, meaning that fire safety measures should be implemented to ensure that fire risks are As Low As Reasonably Practicable (ALARP). However, previous approaches have often been contradictory or unclear, especially with respect to the concepts of risk aversion, the valuation of risk to life, the concept of disproportionality, and the need to take into account monetary benefits resulting from life safety investments. First, the As Low As Reasonably Practicable (ALARP) criterion is specified to a societal, risk-neutral, and scalar cost-benefit analysis in the field of fire safety engineering. This is done to overcome the shortcomings in current practice with respect to utilizing the ALARP criterion for Probabilistic Risk Assessment (PRA).Second, the ethical dilemma of the valuation of risk to human lives is addressed by application of the Life Quality Index (LQI), as has been suggested in the field of structural engineering through the recent ISO 2394:2015 standard. Contrary to the existing literature, the proposed interpretation for the ALARP requirement corresponds to an application of the LQI maximum societal benefit criterion. This ensures that safety resources are allocated so as to maximize the number of lives saved, and implies that the ALARP criterion results in stronger minimum requirements for life safety investments, i.e. societal lower bound investment levels.Third, the valuation of costs and benefits by the fire safety engineer is addressed by emphasizing the duty of care, and by specifying a benchmark criterion for the objective, diligent, and competent fire safety professional. This reinforces self-reflection amongst fire safety professionals, and diminishes the need for often unjustified or poorly specified disproportionality factors.Finally, the relationship between fire safety design and private actor cost-optimization considerations is discussed, and the presented concepts are illustrated using three examples. These clarify the application of the presented concepts and demonstrate how the societal ALARP requirement interacts with the (safety) preferences of private investors. The examples highlight the importance of the societal ALARP evaluation and show that this governs the safety investment when the private investor values damages low, applies a high discount rate, or takes into account indirect costs (e.g. aesthetic costs) related to the safety investment.

Experimental study on the onset of swelling for thin intumescent coatings

Intumescent coatings (also known as reactive coatings) are widely used to protect load-bearing steel structural elements during fire. Upon heating, these initially thin coatings swell to form a low density, highly insulating foamed char that insulates steel substrate. Within the context of modern fire safety engineering design of steel structural systems, thermal insulation during fire may be key for assuring that steel does not reach ‘critical’ temperatures that may yield local structural instability and/or progressive failure (i.e. global instability).Traditionally, the fire performance of intumescent coatings is typically based on compliance (and to some extent their performance) to the standard fire resistance test in furnace, where single coated elements are exposed to the standard temperature-time curve. Numerous research studies have emphasised the influence of heating conditions on the onset of swelling and the overall effectiveness of intumescence. Moreover, some studies have shown that slow growing fires or low heating regimes may cause an incomplete swelling of the intumescent coating, or even melting or delamination. Consequently, the onset of swelling of is key for assuring its effectiveness in providing thermal insulation to the steel substrate during fire. Past researchers have shown that the onset of swelling occurs for temperatures in the range of 200-300°C. There are limited research studies that have look at the effects of varied, non-standard heating regimes on the onset or effectiveness of swelling of thin intumescent coatings.The study presented herein investigates the onset of swelling for a commercially available thin intumescent coating exposed to a wide range of heating regimes. Experiments are performed by using radiant panels and controlling incident radiant heat flux at the exposed surface of coated steel samples. This allows for the direct and precise control of the thermal boundary conditions at the exposed surface of tested samples. The onset of swelling criteria were defined in two ways: (1) visual observation of swelling during heating or (2) time-history of the protected steel temperature.The outcomes of this work aim at yielding a sound understanding of the true effectiveness of thin intumescent coatings. Experimental results mainly show that onset of swelling is directly influenced by the heating regime and it occurs for test samples heated at constant incident radiant heat flux above 20 kW/m2. The onset of swelling for the tested thin intumescent coating occurs for steel temperatures between 150 and 300°C and ‘mean coating temperature’ between 350 and 450°C. However, the steel temperature at onset of swelling is inversely proportional to the amount of constant incident heat flux at the exposed surface of tested samples, while the ‘mean coating temperature’ is directly proportional. As a conclusion, the time-history of net heat flux at the exposed surface of tested samples is not the only parameter that governs the onset of swelling for thin intumescent coatings.

Evacuation response behaviour in unannounced evacuation of licensed premises

SummaryAn understanding of the behaviour of individuals and groups during evacuation is key to the development of evacuation scenarios as part of an engineering design solution. Furthermore, it is important that engineers have reliable and accurate data on pre‐evacuation times and movement for use in time‐based evacuation analysis. This paper presents, for the first time in the published literature, a detailed analysis of an unannounced evacuation of licensed premises and provides important data and understanding regarding behaviour for use in fire safety engineering design and evacuation modelling. Findings on recognition times, response behaviours, pre‐evacuation times and final exit flows for a function room and lounge bar in the licensed property are provided. The results suggest that the evacuation time in the lounge bar was characterised by generally longer pre‐evacuation times and relatively shorter movement times, whereas the evacuation time in the more densely populated function room was characterised by shorter pre‐evacuation times but extended flow times. The paper highlights important design and management issues with respect to the evacuation of persons under the influence of alcohol and considers the impact of staff intervention through directed voice communications. The variation in response behaviours between the two separate areas of the premises are highlighted and discussed. Copyright © 2017 John Wiley & Sons, Ltd.

Thermal characteristics of externally venting flames and their effect on the exposed façade surface

In a compartment fire, Externally Venting Flames (EVF) may significantly increase the risk of fire spreading to adjacent floors or buildings, especially when combustible insulation materials are installed on the building façade. An increasing number of recent reports suggest that existing fire engineering design methodologies cannot describe with sufficient accuracy the characteristics of EVF under realistic fire load conditions. In this context, a series of fire safety engineering design correlations used to describe the main EVF thermal characteristics, namely EVF centreline temperature and EVF-induced heat flux on the exposed façade surface, are comparatively assessed. Towards this end, measurements obtained in a medium- and a large-scale compartment-façade fire test are employed; aiming to broaden the scope of the validation study, predictions of the investigated correlations are further compared to measurements obtained in 6 large-scale fire tests found in the literature. It is found that the correlation proposed in EN1991-1–2 (Eurocode 1) for the estimation of the EVF centreline temperature is under-predicting the measured values in large-scale fire tests. In addition, it is concluded that estimation of the local flame emissivity should take into account the specific fuel type used in each case.

Experimental and numerical evaluation of the influence of the soot yield on the visibility in smoke in CFD analysis

Experimental and numerical analysis have been performed to evaluate the influence of the soot yield parameter on the results of advanced engineering analysis, in regards to visibility. After identifying soot yield as the most influential factor on the results, fuels with various values of Ys have been analysed in a fire chamber and then compared to numerical data. The numerical analysis has been performed using two different CFD packages, ANSYS® Fluent®, and Fire Dynamics Simulator. The numerical analysis itself show an apparent hyperbolic trend of the visibility when changing the soot yield with clear consequences on the ASET (Available Safe Egress Time). Below a cut-off point, that exists at a soot yield value close to Ys =0,10g/g, a small change in the parameter causes a substantial shift in the results (visibility or ASET time), while above this value an increase to soot yield does barely influence the results. Qualitative assessment of the results shows a need for use of conservative values of Ys in engineering analysis if detailed and precise material data is not available. Additionally to the full-scale experiments, a real case study has been included to show how this research can be translated into the Fire Safety Engineering design process. In this study, change of Ys value below 0,10g/g caused a significant change of the qualitative assessment of the results of CFD.

Editorial: Fire safety engineering design of concrete structures

Editorial: Fire safety engineering design of concrete structures

Philip Humphrey Thomas (16 June 1926 – 14 January 2014)

Philip Humphrey Thomas (16 June 1926 – 14 January 2014)

A Dynamic Approach to ASET/RSET Assessment in Performance based Design

The basic concept in the assessment of occupant safety in a building under fire conditions is the determination of the time when occupants are able to safely escape before hazardous conditions sets in. The Available Safe Egress Time/Required Safe Egress Time (ASET/RSET) concept of fire safety assessment in performance based fire safety engineering design has become widely used amongst fire safety engineering practitioners, since its inception more than thirty years ago. However, the adequacy of this approach has only been occasionally deliberated on and not well addressed in detail. Discussions were usually focused on the weaknesses and inadequacies in the assumptions and methodologies which impact upon the outcome of the ASET and RSET parameters, rather than on the ASET/RSET concept itself. The original ASET/RSET approach was derived from a simple two-zone model for a single compartment by Cooper in 1980, but is still being applied to larger and more complex buildings today. This is despite the advancement of sophisticated three- dimensional simulation models producing highly detailed results, whereby the smoke layer is no longer uniform and the extent of the area of untenable conditions is a transient state and may develop only over a portion of the compartment area. The continued application of the ASET/RSET approach in these circumstances may lead to varied interpretation of the egress terms, leading to departures from the intended purpose and scope of providing the basic measure of assessing egress safety that was originally devised by Cooper. There is also little published literature available on viable alternatives to this simplified means of assessing safe egress from fire that was originally derived from a zone model concept. This paper provides a brief review of the ASET RSET methodology, and introduces an alternative means of fire safety assessment based on the utility of a given space over time. The alternative scheme enables a dynamic approach to assessing the level of safety that is more appropriate for use with advanced simulation models providing transient three-dimensional environments in more complex building layouts.

Application and Limitations of a Method Based on Pyrolysis Models to Simulate Railway Rolling Stock Fire Scenarios

This article relates the application of pyrolysis models to products used onboard trains, as part of a fire safety engineering design or assessment. It is based on work performed during the European Research program, TRANSFEU. As a first step in the methodology, risk analysis permits identification of the most critical scenarios to be studied, considering actual operational conditions and rules in the European railway network. The study of one such scenario has been performed using advanced numerical tools and a multi-scale approach from raw material to real scale, in order to validate the application of such techniques in fire risk assessment. Simulations have been compared to experimental data at each scale. This predictive method shows a good capability to properly reproduce fire growth, heat release rate, temperatures and carbon dioxide concentrations in a real-scale scenario. On the other hand, this study highlights poor prediction of concentrations of carbon monoxide and other toxic species.

Fire safety engineering at a crossroad

Fire safety engineering (FSE) has become widely accepted throughout the world. This is quite an accomplishment for a young engineering discipline. Fire safety engineers are employed by public and private sector organizations of all types. We are involved in almost all major building and infrastructure projects, enabling amazing buildings to be designed, constructed and occupied. We play critical roles in high hazard industries, helping to mitigate risks and achieve acceptable levels of safety. We undertake groundbreaking research and develop new technologies aimed at reducing the impacts of unwanted fire. However, as an engineering discipline, we lack several attributes that one might expect to see in a mature discipline, including a robust analytical engineering framework. We have not experienced any transformational changes in technology or practice in some time. FSE degree programs and recognition of FSE as a unique discipline remain lacking in several countries, leading to wide variation in the level and consistency of fire safety performance delivered. This has unfortunately led some to question the competency and the efficacy of the profession, in some cases resulting in more regulatory control over the fire safety engineering analysis and design of buildings. The net result is that we are at a crossroad. We face some significant challenges, but we have the opportunity to shape an amazing future. If we are up to the challenges and take advantage of the opportunities, we have a chance to evolve the discipline towards maturity and greater respect. In this article I outline my view of the current situations, some of the challenges we face, steps we might take to overcome them, and areas for research, development and implementation into practice concepts that can lead to a promising future.

A nascent educational framework for fire safety engineering

The growing need for fire safety engineering (FSE) design around the world has led to higher education degrees, many of which lack strong foundations in fundamental knowledge and are somewhat deficient in developing skills (application of knowledge) and appropriate attitudes (reflective assessment and synthesis of knowledge). This paper discusses how such programmes are delivering professionals to an FSE industry that has not yet adequately defined competence. Motivated by the need to have a new generation of leaders in FSE that can drive the field through the ongoing and necessary transition to performance-based design that it is currently experiencing, a one-week, intensive global technical leadership seminar was held at Edinburgh University, supported by The Lloyd's Register Educational Trust (LRET). The Seminar was aimed at reflecting on the content and methodology required in comprehensive university programmes capable of educating in design for fire safety in the built environment. Performance-based design for fire, in which prescriptive codes are simply a tool within a performance-based mindset, offers many important benefits but also has many acknowledged problems and risks; this paper argues that paramount among the problems is the way that we, as a global engineering profession, educate and nurture FSE professionals. It is argued that fire safety is a relatively immature discipline, thus it should be supported by holistic, purpose-centred education that places an emphasis on learning environments broadly focused on design. Technical (fundamental) knowledge is clearly critically important, but it should not be the driving force, and it should not eclipse the development of the skills and attitudes essential for the future survival of fire safety engineering as a distinct, competency-based engineering discipline.

Review of Indonesian Standard for Concrete Building Subjected to Fire

Abstract Fire safety engineering design of concrete structures in Indonesia is principally based on individual member from results of isolated beams, columns, and slabs tested in small furnaces. However, researchers identify that the behaviour of individual isolated members is significantly different from behaviour of complete structure connected together when subjected to fire. Although the current guidance is conservative when the entire building performance is considered, it should be noted that the beneficial and detrimental effects in complete structures should be taken into account. The effect of concrete spalling in fire has also not been enclosed sufficiently in the code. It should also be noted that the reduction of steel reinforcement cover could generate premature collapse of the structures. Since designers and engineers need to understand the behaviour of entire structure in fire, developing engineering guidance based on realistic structural behaviour is essential.

The Effect of Natural Wind to the Atrium Building Smoke Migration

With the rapid economic development of our country, the speed of city construction is accelerated and more proposed development with super high and super large space construction has appeared, hence the relevant fire problems are still a challenge. It's acknowledged that performance-based design provides more reasonable and innovative design strategies for fire engineers. The CFD simulations are always executed to validate the feasibility of performance - based design. Current fire safety engineering design and fire engineering researches are focused on the fire generating and smoke migrating in the building. Seldom consideration is given on how the natural wind of outside the building affects the smoke migration pattern. However, it will be unrealistic that ignore the natural wind factor in smoke control design. Especially, it will be unacceptable in the natural wind smoke control design which utilizes the natural wind to exhaust smoke out of the building. As well as more investigations will be required in the mechanical smoke control design. The paper integrates the PHOENICS which is the general purpose CFD software with the statistic data about the natural wind from the specific area/city to analyze how the natural wind can impact on the fire and smoke generated in the atrium of a large space building, so as to provide some references for the future smoke control designs.

Analysis of Composite Floor Cellular Steel Beams in Fire

The growing popularity of the use of cellular steel beams in composite floors comes at the same time as an increasing attention to the fire safety engineering design. The recommendation for their design in fire limit states remains very primitive and this is due to the lack of general research in this area. Four composite cellular steel beams were tested at the University of Ulster with two models of different steel geometries and loading conditions under monotonic loading and at elevated temperatures. This paper presents a finite element model and simple hand calculation methods to calculate the shear buckling at the web post, the bending resistance in fire, deflection and temperature distribution in the cross section of composite cellular beams.

RSET/ASET, a flawed concept for fire safety assessment

AbstractFor the evaluation of occupant safety in the case of building fires, the Required Safe Egress Time/Available Safe Egress Time (RSET/ASET) concept has become widespread and is now commonly used in the fire safety engineering profession. It has also become commonly used by smoke detector (smoke alarm) manufacturers in assessing whether a particular detector technology is adequate. It is shown in this paper that the concept is intrinsically flawed and its use promotes the diminishment of fire safety available to building occupants. The concept innately ignores the wide variations in capabilities and physical condition of persons involved in fire. It is based on implicitly assuming that, after a brief period where they assess the situation and mobilize themselves, occupants will proceed to the best exit in a robotic manner. This assumption completely fails to recognize that there are very few fires, especially in residential occupancies, where occupants perished or were seriously injured who had endeavored to exit in this robotic manner. Instead, in the vast majority of fire death and serious injury cases, the occupants did not move in such a manner and their evacuation took longer than anticipated on the basis of robotic movement. There is a wide variety of reasons for this, and these are well known in the profession. The concept also ignores that there can be a wide variation in fire scenarios. The same building and the same fire protection features can be evaluated, but both RSET and ASET can change drastically, depending on the scenario used. The consequence of using the RSET/ASET concept for fire safety engineering or product design purposes is that fire deaths and injuries are permitted to occur, which are preventable. Copyright © 2010 John Wiley & Sons, Ltd.

Oscillating behaviour of fire-induced air flow through a ceiling vent

Oscillations of fire-induced air flow through a ceiling vent in a compartment will be studied in this paper. The equations describing the oscillations of air flow induced will be discussed first. Air flow through the vent is found to be induced by buoyancy or by pressure. A wave function was introduced as a perturbation to a control volume concerned. Oscillation growth, amplification, response and frequency will then be studied by solving these key equations under practical conditions. Useful semi-empirical formula on those parameters is derived for fire safety engineering design. The predicted results will be discussed and compared with experimental data available in the literature.

Heat fluxes on opposite building wall by flames emerging from an enclosure

Flames emerging from an opening of a fully developed burning room are the main path of a fire spreading from floor to floor and to an adjacent building. Even though the issue of fire spread to an adjacent building has been incorporated in fire safety engineering design guidelines, performance-based design provides an alternative and accurate method to optimize the distance between the building façade with a burning enclosure and an adjacent building. This situation was simulated by performing a series of small scale experiments having a façade wall with flames and an opposite parallel wall representing an adjacent building in order to investigate the physics of the flame behaviour and measure the heat fluxes between two walls. The outcome of this research provides unique information for engineering design for separation distances between adjacent buildings. A new length scales, ℓ 3, representing the length after which the flames turn from horizontal to vertical was developed in this research. The significance of this length scale has been verified by the experimental results for flame heights and heat fluxes and by observations. Similarity correlations for flame heights between the two parallel walls were developed in this research. Similarity correlations for radiative heat fluxes on facade walls were developed by dividing the data into two groups. One is for the distance between two walls being larger than length scale ℓ 3, the other is for the distance being less or equal to length scale ℓ 3. Measurements of the heat fluxes on the opposite wall allow also the determination of the total radiant output.