Fire Engineering Design Research Articles

Experimental Study on the Fire Resistance of Rectangular Hollow Sections Steel Columns

A fire occurring at a building causes severe damages to its structural members and brings unexpected collapse. Therefore, the building regulation of each nation has to define fire resistance to prevent building collapse due to high temperatures. In general, the fire resistance of each structural member can be evaluated by two methods. One is prescriptive method that is guided by a specific building regulation containing fire resistance examples or by the application of new examples tested fire experimental procedures. The other is performance based fire engineering design. Being an engineered and scientific method, it utilizes the results obtained from the calculation of fire severities, temperatures of members and so on. The easiest way to evaluate the fire resistance of a steel member is to compare its limiting temperature and maximum temperature. Therefore, constructing the database of the limiting temperatures of structural elements is very important in performance based fire engineering design. This paper is to derive the fire resistance and limiting temperatures of rectangular hollow sections under loads.

Experimental justification on thermal empirical equations for post-flashover compartment fires

Many useful correlation equations derived for estimating the heat release rate for a postflashover room fire were applied in performance-based design. A postflashover room fire is very hazardous as demonstrated by several big accidents in the past few years. The authorities are starting to challenge the use of such equations as fire engineering design tools. Additional justification of the results with experiments in fire hazard assessment is now required. Two correlation equations on heat release rates with gas temperature for postflashover fire are commonly used. One was reported by Babrauskas and Williamson and the other by McCaffrey et al., denoted as BW and MQH equations, respectively. Both equations were justified in this article by reported experimental data. Two sets of reported experimental results on postflashover room fires with transient heat release rates measured by oxygen consumption calorimetry were used. One set was reported by Chow et al. on studying flashover in a compartment fire with gasoline pool fires up to 2.8 MW. The other set was the experimental data on cable fires in a long cavity reported by Hietaniemi et al. Direct comparison indicated that heat release rates estimated using the BW equation are lower than measured values of both sets of the experiments. This point should be watched while applying the BW equation in fire hazard assessment. Better agreement was observed in the equation by MQH. A possible reason is that the empirical constants in the MQH equation were deduced by fitting with experimental data.

Ensuring Resilience in Building Design Using Fire Engineering

As an engineering discipline within the United Kingdom, fire engineering is relatively young. It has been accepted as an alternative to traditional prescriptive means of meeting the functional requirements of the Building Regulations since the publication of the 1985 edition of Approved Document B. Performance-based fire engineering design methods have facilitated architectural design freedoms and supported creative construction. However, it has become evident that since fire engineering has become more established, significant concerns have been raised regarding various elements of the design process including the ability to consider aspects other than life safety which may result in a poorer overall response of the building to fire, while achieving the life safety ambition. In response to these concerns, this article introduces novel concepts to assist the building design team consider their client's resilience requirements by utilizing business continuity planning methods. Using business impact analyses within the qualitative design review will identify those processes which are allowing the most appropriate fire engineering strategy to be established. This new approach to fire engineering design is to be formally described within a new part of the established British Standard which defines a fire engineering procedure.

Detection of a typical arson fire scenario - comparison between experiments and simulations

Abstract in Undetermined Between one and two school fires occur in Sweden every day. In most cases, arson is the cause of the fire. The most severe fires generally start outside the building and spread up along the facade and into the attic through ventilation openings in the eaves. Linear heat detectors can be placed on facades to detect these types of fires. Such devices detect fire when short-circuited at a specific temperature. In this article, an attempt to simulate linear heat detectors is presented. Data from small-scale and full-scale experiments are compared with these simulations. The small-scale experiments and simulations demonstrate that the cable failure model in Fire Dynamics Simulator can be used to predict detection in linear heat detectors that use short-circuiting as the means of signaling an overheated condition. The full-scale experiments provide a measure of the uncertainties involved, as well as the possibility of using simulations of linear heat detectors in a fire engineering design. (Less)

A simplified calculation method on maximum smoke temperature under the ceiling in subway station fires

To assess the impact of smoke on the ceiling in subway stations, the maximum smoke temperature under the ceiling was studied theoretically and experimentally with two sets of small-scale experiments conducted. The results show that the maximum smoke temperature under the ceiling complies with the Alpert equation in which fire keeps distant from the walls in subway stations whereas fire adjacent to the end wall leads to the maximum smoke temperature under the ceiling decaying exponentially against the increased distance between the fire and the wall. In addition to the Alpert equation, a correlation determining the maximum smoke temperature is developed by taking the end wall effect into account. Consequently, a simplified calculation method involving the Alpert equation and the correlation is established. The method is applicable to practical fire engineering designs for subway stations.

A connection element for modelling end-plate connections in fire

In this paper a robust 2-noded connection element has been developed for modelling the bolted end-plate connection between a steel beam and column at elevated temperatures. The connection element allows the element nodes to be placed at the reference plane with offset and the non-uniform temperature distributions within the connection. In this model the connection failure due to bending, axial tension, compression and vertical shear are considered. The influence of the axial tensile force of the connected beam on the connection is also taken into account. This model has the advantages of both the previous simple and component-based models. A total of 23 fire tests were used to extensively validate the model. It can be seen that the current model is robust and has a capability to predict the behaviour of a bolted end-plate connection under fire attack with reasonable accuracy. Compared to the tested results the predictions of the current model were mainly on the conservative side. Hence, the model can be used for structural fire engineering design on steel-framed composite buildings. The idea described in this paper can also easily be applied to develop other kinds of connections, such as simple connections, column based connections or hollow section connections, and so on.

Challenges of Fire Fighting in Fire Engineered Built Environment

Performance based fire engineering design, as opposed to the traditional approach of satisfying highly prescriptive rules, is increasingly being taken up by clients and their professional advisers, including architects and engineers, because the performance based design approach can be used to offer a more attractive design through cost saving and greater design flexibility. However, fire engineering solutions make different assumptions on fire services intervention and are based on a number of engineering and management assumptions. These assumptions have implications on activities of the fire authority, in particular, fire fighting activities and these should, at the design stage, be addressed by the fire engineering design team. It is also important that the fire authority works closely with the fire engineering design team so that the fire engineering assumptions are not invalidated by fire service intervention. This paper identifies a number of challenges facing both the fire engineering design team and the fire authority and discusses how some of the challenges may be tackled.

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.

Mechanical and thermal properties of SM 490 at high temperature for fire engineering design

The use of structural steels is rapidly increasing in the high-rise building market in Korea because of its higher quality, construction period, and lower cost than the ordinary construction materials such as concrete. However, steel structures have a serious drawback. Severe fire conditions tend to weaken them and they can collapse. To overcome this weakness, steel structures must meet the fire resistance requirements in the building laws or building codes of the respective country. In Korea, the method for evaluating fire resistance in steel structures is currently being developed with performance based engineering. Fire engineering offers calculation methods for evaluating fire resistance. The calculation depends on the accurate mechanical and thermal data of the materials at high temperature. The purpose of this paper consists of two parts: one is to obtain data on mechanical properties at high temperature and to gather thermal data, and the other is to compare the calculation with an experimental fire test. By using the results of tensile strength tests conducted at high temperature, the regressive equation for yield strength and elastic modulus of structural steel were derived. Increasing patterns of temperature from cold to high were very similar between the results of analysis and those of fire tests. This similarity held until the half of fire resistance was obtained.

Survey on passenger loading in the Hong Kong airport terminal

Emergency evacuation is the main concern in crowded airport terminals. Data on occupant loading are important for designing means of escape. However, very few field survey data on crowded terminals are available in the literature. There are queries concerning whether the data specified in the prescriptive codes are realistic in designing safety systems in modern terminals. More questions have been raised for those terminals using data, such as maximum floor area allowances per occupant, from the prescriptive codes which have not yet been verified for carrying out performance-based fire engineering design. In this study, passenger loading in the Hong Kong airport terminal was investigated. A field survey was carried out, in which the performance-based design was based on the occupant loading factor extracted from the prescriptive codes of Hong Kong. Transient passenger loadings of the airport in different seasons were compiled. The results were used to justify the maximum allowed loadings specified in design codes and standards.

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.

Slab panel vertical support and tensile membrane action in fire

The increasing use of performance-based approaches in structural fire engineering design of multi-storey composite buildings has prompted the development of various tools to help quantify the influence of tensile membrane action in composite slabs at elevated temperatures. One simplified method which has emerged is the Bailey-BRE membrane action method. This method predicts slab capacities in fire by analysing rectangular slab panels supported on edges which resist vertical deflection. The task of providing the necessary vertical support, in practice, requires protecting a panel's perimeter beams to achieve temperatures of no more than <TEX>$620^{\circ}C$</TEX> at the required fire resistance time. Hence, the integrity of this support becomes critical as the slab and the attached beams deflect, and large deflections of the perimeter beams may lead to a catastrophic failure of the structure. This paper presents a finite element investigation into the effects of vertical support along slab panel boundaries on the slab behaviour in fire. It examines the development of the membrane mechanism for various degrees of edge-beam protection, and makes comparisons with predictions of the membrane action design method and various acceptance criteria.

Experimental investigation of the behaviour of fin plate connections in fire

Accidental fires and full-scale structural tests have indicated that steel connections can be subjected to large deformations and fracture in fire. This is not currently considered in fire engineering design approaches because the connections are assumed to heat up more slowly than the structural frame members and therefore retain a greater proportion of their strength. A project at the Universities of Sheffield and Manchester has investigated the robustness of common types of steel connections when subjected to fire. In the test programme the connections were subjected to combinations of shear force and tying force, and loaded to large deformation and fracture. This paper reports on the test results on fin plate connections. The test results indicate that bolts are vulnerable to shear fracture and that failure is usually controlled by bolt shear rather than by plate bearing. Fin plate connection resistance reduces rapidly with increase of temperature. The test results are compared to values suggested by the current United Kingdom design guidance and Eurocode 3 Part 1.8. A previously developed component-based model is also used to simulate the test results.

A study on the effect of project coordinators' knowledge on the use of performance-based fire safety engineering design in buildings

Alternative fire safety design is prima fasciae permitted in Hong Kong's legislative context. It is further explicitly allowed through the 1995/1996 fire safety-related building codes, that is, a performance-based track has been initiated for the past decade. Hong Kong certainly cannot be regarded as the first city/country to engage in such an effort. United Kingdom, for instance, has explicitly allowed the use of fire engineering in the 1985 Building Regulations. However, it has been noted that the building projects' coordinators, architects, building surveyors, engineers, etc, do not usually have much knowledge on the use of fire safety engineering (FSE) design. Such a situation may affect the extent of projects using performance-based approach. This paper presents a simplified system dynamics model to examine the effect of project coordinators' awareness on the use of FSE design in Hong Kong.

Sharing Building Information using the IFC Data Model for FDS Fire Simulation

This paper describes part of a research project that looks into the potential and challenge of using the Industry Foundation Classes (IFC) open standard building information model in fire engineering design. In particular the paper describes work undertaken to share building geometry and other information with the Fire Dynamics Simulator (FDS) fire simulation model. A commercially available building information modeling (BIM) authoring application has been used to create building geometries and export IFC data files. A web-based conversion tool has been created to generate FDS input data given the output from a dedicated fire engineering IFC parser tool. The capabilities and outcome of data sharing process is illustrated in this paper using a simple test case building.

A Comparative Analysis of the Use of Different Zone Models to Predict the Mass Smoke Flow for Axisymetric and Spill Plumes

Sanderson [1]examined the theoretical basis for and the experimentation supporting the predictive smoke zone models currently being used in fire engineering design that are cited, in nationally and internationally accepted guidance documents, to support the increasing use of performance-based building codes/regulations throughout the world. This critical examination identified anomalies: 1) between different researcher’s results, when considering the same fire environment, and 2) areas where the models used in guidance documents have limited empirical support. The variance between models was examined by the parametric variation of critical data input parameters the impact of which indicated that the most recent research produced models that predict a lower level of mass smoke flow than the earlier models. It may be suggested that the more recent research, building on previous work, produces models that can be used with a greater level of confidence however there is no robust evidence to support this. This paper illustrates the variances between the model outputs by means of a case study. Currently there is a move towards the use of Computational Fluid Dynamic modelling of fire. However, given the limited validation of these models in the area of smoke movement and the computer time and power required to run these models, there is still a place in fire engineering design for the zone model. As an increasing number of countries adopt performance building and fire codes/regulations and given the consequent need for predictive mass smoke flow models in which regulators, fire engineers and society can have confidence, it is concluded that the research supporting zone modelling of fire should be extended. This research should be robust and transparent in order to either produce models that are substantially more acceptable than those currently being used or to provide more confidence in models.

Local buckling and slenderness limits for steel webs under combined bending, compression and shear at elevated temperatures

At elevated temperatures induced by fire loading, the I-section beam and column elements in a steel framed building experience combinations of axial, bending and shearing actions that may precipitate local buckling of the steel element. Under this loading regime, the Young's modulus, shear modulus and uniaxial yield strength may vary through the section depth because of the temperature gradient, and as a result predicting the local buckling capacity and the critical geometrical slenderness for coincident elastic local buckling and yielding are not straightforward. This paper presents an analysis of the elastic local buckling of the web of an I-section beam, by modifying a spline finite strip method of local buckling analysis to include the variation of material properties through the web. Necessarily, the method must also include the variation of mechanical strains through the web depth, in order that the limiting depth to thickness ratio that delineates yielding and elastic buckling (and hence the cross-section classification) can be prescribed. Under the combined loading, it is shown how the elastic local buckling coefficient and the web slenderness limit that classifies a non-compact section are dependent on the thermal gradient, the depth of the compression zone in the representation of the mechanical strain, and on the values of the shear strain. Graphical results are presented for the elastic local buckling coefficients as a function of the temperature and of the temperature gradient in a web with idealised edge restraint conditions. Since the local buckling response is crucial in establishing the formation hinges in flexural elements in the initial stages of thermal loading prior to the subsequent development of catenary action, the results are valuable for undertaking a rational fire engineering design of the steel elements exposed to a compartment fire, and they lend themselves to a codified approach for the structural behaviour.

Fire analysis of steel frames with the use of artificial neural networks

The paper presents an alternative approach to the modelling of the mechanical behaviour of steel frame material when exposed to the high temperatures expected in fires. Based on a series of stress–strain curves obtained experimentally for various temperature levels, an artificial neural network (ANN) is employed in the material modelling of steel. Geometrically and materially, a non-linear analysis of plane frame structures subjected to fire is performed by FEM. The numerical results of a simply supported beam are compared with our measurements, and show a good agreement, although the temperature–displacement curves exhibit rather irregular shapes. It can be concluded that ANN is an efficient tool for modelling the material properties of steel frames in fire engineering design studies.