Compartment Fire Research Articles

Performance-Based Evaluation on Egress Safety of Nursing Hospitals Considering Egress Guides and Delay Time

In recent years, the number of nursing hospitals has significantly increased as the number of elderly has increased. However, since there are many patients who have difficulty in moving quickly in the nursing hospitals, it is very hard to evacuate rapidly in the event of a fire, which results in many casualties. In this study, fire and evacuation simulations for the nursing hospital were performed, based on which the evacuation safety was evaluated in detail according to the location of the fire compartment, number of evacuation guides, and evacuation delay time. The simulation results showed that it is necessary to secure the number of evacuation guides complying with the legal standards, and to reduce the evacuation delay time to be less than 60 s in order to avoid loss of life.

Evaluation of the room smoke filling time for fire plumes: Influence of the room geometry

SummaryThe article examines numerically and theoretically the effects of room aspect ratio on the fire smoke filling process. It aims to evaluate the two‐zone models used in fire safety engineering to predict the smoke filling times. Using Fire Dynamics Simulator, numerical simulations are performed and compared to a simplified zone model. The results show that the two‐zone model overestimates the smoke filling time in the case of a compartment with a large surface area. To improve the predictions of two‐zone models, simple correlations are established for the duration of the phenomena occurring before the formation of a two‐layer stratification in a fire compartment. These new correlations allow the zone model to be significantly improved.

Experimental investigation into fire behaviour of glazed façades with pendant type sprinklers

Façade systems play an important role in fire compartmentation of a building and reducing the likelihood of fire spreading through and outside of the building walls. The use of sprinklers in building regulations often allows for smaller building separation. However, no additional benefits are usually given to additional internal sprinkler protection of the external glass façade using standard pendant sprinklers. Four compartment fire experiments were performed with non-fire-rated aluminium façades with two- and three-layered Insulating Glass Units (IGU), protected by pendant-type sprinklers (DN15, K-factor = 80, T = 68 °C). Sprinklers were in row 14–55 cm from the glazing, with 1.514–1.83 m separation distance. In all experiments, façades achieved satisfactory performance in terms of glazing integrity, insulation and reducing the thermal radiation. Under a non-uniform water distribution, parts of the glass were dry (1.7%–15.7% of IGU area), where we have observed soot deposition and local damage to fire exposed glass layer, but no loss of the structural integrity. The temperatures on the unexposed side did not exceed 86 °C, the peak measured temperature of the internal glass surface was 173 °C. The performed experiments confirmed the capability of standard pendant-type sprinklers to enhance the fire protection features of a building façade.

A Numerical Analysis of the Fire Characteristics after Sprinkler Activation in the Compartment Fire

Understanding fire characteristics under sprinkler spray is valuable for performance-based safety design. However, fire characteristics during fire suppression by sprinkler spray has seldom been studied in detail. In order to present a fire suppression model by sprinkler spray and determine the fire characteristics after sprinkler activation in a compartment, a numerical analysis was conducted using a fire dynamics simulator (FDS). A simple fire suppression model by sprinkler spray was calibrated by comparing ceiling temperatures from experimental data. An extinguishing coefficient of 3.0 was shown to be suitable for the fire suppression model. The effect of sprinkler spray on the smoke layer during fire suppression was explained, revealing a smoke logging phenomenon. In addition, the smoke, which spread under the influence of the sprinkler spray, was also investigated. The temperature, velocity, and mass flow rate of the smoke layer through the doorway was significantly reduced during fire suppression compared to a free burn case.

Performance of a ventilated‐façade system under fire conditions: An experimental investigation

SummaryDuring a fire event, ventilated facade systems may contribute to external fire spreading to the upper floors of a building via the facade, thus representing a significant risk. In this frame, the performance of a typical ventilated façade system under fire conditions is experimentally investigated, using a full‐scale compartment‐facade test rig. Two alternative façade configurations are examined and comparatively assessed, namely a plain façade (PF) and a ventilated façade (VF) system. Emphasis is given on the estimation of the thermal characteristics of the developed Externally Venting Flames (EVF) and the thermal boundary conditions developing on the façade's exposed surface. An extensive set of sensors was installed at the interior of the fire compartment, the façade systems and the exterior of the test configurations. Analysis of the experimental data suggests that even though gaseous combustion products managed to penetrate the air cavity of the VF system, no consistent flaming conditions were established. On the unexposed face of both PF and VF systems, temperatures remained constantly below 180°C throughout the duration of both fire tests. The Eurocode correlations are assessed against the obtained experimental data; certain parameters, such as EVF length, width and centreline temperature, are found to be under‐estimated by the Eurocode methodology.

The Influence of Steel Connection on Fire Resistance of Composite Steel-Framed Buildings

Steel connections play a significant part in enhancing the robustness of structures in the event of a fire. Therefore, it is important to examine the impact of steel connections on the fire resistance of composite steel framed buildings. In this paper, both the behaviour of steel connections and their effect on composite steel frames are analysed using the non-linear finite element computer software VULCAN at various temperatures. The chosen frame is subjected to ISO834 fire. A comparison between end plate connections, pinned connection and rigid connection has been carried out. By applying different compartment fires, some cases are studied to show the behaviour of steel connection when the fire is applied at certain beams. In addition, different plate thickness has been analysed to examine the behaviour of the chosen steel connection under ISO834 fire. From the analytical results, it was found that the beam with extended end plate is stronger and has better performance in terms of axial forces than those beams with flush end-plate connection. Furthermore, that extended end plate connection has highest limiting temperatures compared to the flush end plate connection. In addition, it was observed that the performance of end-plate connections is very close to rigid connection and very far from pinned connections. Furthermore, plate thickness has less of an effect on the influence of steel connection in regards to fire resistance. The article will conclude that the behaviour of composite steel framed buildings is largely dependent on the steel connection due to their high impact under fire condition. It is recommended to consider the extended end-plate in the design proposals because of its higher fire resistant properties compared to the flush end-plate connection. Finally, this paper shows that steel connection has an important effect on the fire resistance of composite steel framed buildings.

Spatiotemporal measurement of light extinction coefficients in compartment fires

Spatiotemporal measurement of light extinction coefficients in compartment fires

Development of solid propellant for the production of fire suppression aerosols

This paper documents the development of solid propellant aerosol generators (SPAGs) as alternative fire suppression systems. SPAGs mainly consist of an igniter, a solid propellant (SP), a cooling system and an outlet. The main focus of this study is on the SP as the research item. Such SP consists of oxidant, fuel and additives. This research work aimed to investigate the application of the aerosol produced by a SP as a potential fire suppression agent. The first step in this regard involved a numerical calculation, using RPA® software which is designed for and used in rocket engine applications, to define a number of combustion and thermodynamic parameters related to the SP. This was followed by a parametric study of different SP compositions and their respective fire suppression aerosols (FSAs). The SPs that produced the highest fraction of FSA were chosen for an experimental comparison. A special experimental setup was developed for this comparison and data were generated by performing more than 100 tests. The experimental data showed that the selected SP are able to suppress small n-heptane pool fires in compartments effectively, validating the results of the RPA® calculations. The experimental data proves that the suppression effect is inhibition.

Exploratory fire analysis in DONES lithium system

The exploitation of Nuclear Fusion energy in power plants will require the development and qualification of materials able to withstand outstanding neutronic loads for which no operating experience is currently available. Therefore, a Demo-Oriented early NEutron Source (DONES) facility for material irradiation is currently being designed within EUROfusion programme aimed at the production of neutrons with fusion relevant spectrum and fluence by means of D – Li stripping reactions occurring between a deuteron beam impacting a stable liquid lithium flowing film implementing the target. The Lithium System (LS) in DONES shall provide circulation of liquid lithium with suitable thermal-hydraulic characteristics and assure impurity control and heat removal. Given the hazard constituted by liquid lithium inventory and the potential risk of reactions with air eventually resulting into fire events, a preliminary evaluation of the modality of occurrence and evolution of such abnormal events in LS has been performed. In particular, two events have been selected for fire analysis. The first event considers a failure of off-line sampler equipment with water getting in contact with sampled lithium inventory. The initiating event is a failure in the glove box containing the off-line sampler. An air ingress occurs in the glovebox and a break of the Li flask is hypothesized at the same time. The second event assumes a leak at the outlet of the electromagnetic pump with loss of Lithium from the Li pipe in Heat Rejection System in LS room. Simultaneous air ingress is hypothesized as well in LS room (normally filled with inert argon). Fire loads were initially identified for the selected events and the room models developed considering dimensions, lithium inventory and fire compartment assumed to coincide with room limits. The ignition of lithium in contact with air occurs at liquid lithium operating temperature as reported in most conservative observations in literature and lithium fires were simulated as heat flux associated to lithium – air reactions rates observed in literature. A model for both events was implemented in Fire Dynamic Simulator (FDS) code to evaluate fire dynamics and a sensitivity analysis was performed on relevant inventories in the lithium loop area to investigate possible consequences.

Symmetric modeling of the thermal actions in a structural fire experiment on a long-span composite floor beam in a compartment

This paper presents symmetric modeling of the thermal actions in a structural fire experiment on a 12.8 m long composite floor beam in a compartment. A quarter of the fire compartment was modeled in FDS and a portion of about 1/160 of the composite beam was modeled in ANSYS. The FDS symmetry model gave consistent results with the FDS model of the entire compartment, the differences between the predicted upper layer gas temperatures were within 2 ∘C on average. The differences between the FDS symmetry model predicted upper layer gas temperatures and the experimental data were within 7% at the steady stage. Using the thermal boundaries predicted by the FDS symmetry model, the finite element symmetry model gave good prediction of the lower flange and mid web steel temperatures of the composite beam, the differences between predicted and measured maximum lower flange and maximum mid web temperatures were within 2%. The study indicates that symmetry model might be used to predict the thermal responses of structures in realistic fires.

Experimental investigation on maximum ceiling jet temperature generated by a vertically spreading cable fire

Maximum ceiling jet temperature (MCJT) is an important parameter for evaluating fire risk. An important characteristic of vertical cable tray fire is the upward spreading of the cable flame along the cable tray, which leads to a decrease in the distance between the fire source and compartment ceiling during such a fire. Thus, full-scale fire experiments using vertical cable trays were conducted in a confined compartment to investigate the MCJT. The upward spreading of the cable flame leads to transition of the MCJT dominated by the plume region to intermittent region of the flame. In particular, it is observed that the MCJT suddenly increases from ~200 °C to more than 600 °C at this transition point. Taking the upward spreading cable flame along the vertical cable tray as a point fire source moving with constant velocity, a modified model is proposed to estimate the MCJT. Prediction using the proposed modified model yields promising results. The local prediction error for the modified model is less than 12%, and the global prediction error is between 23.6% and 38.6%. These errors are significantly lower than those for other models that assume a fixed fire source.

Fire dynamics in mass timber compartments

Since Engineered Wood Products (EWPs) have entered the building industry as structural elements, several fire safety concerns have arisen, especially for high-rise structures.The combustible nature of timber suggests that the current models and correlations for compartment fire dynamics might not apply to compartments with timber boundaries, due to the increased fuel load and its redistribution across the compartment.In order to fill this knowledge gap, 24 medium-scale timber compartments have been carried out to characterise the fire dynamics when timber members are present.This experimental campaign provides data about the gas-phase temperatures, the flow fields at the opening, the burning behaviour of timber and its contribution to the total heat release rate. This data is then compared to Thomas and Heselden (1972) [1] compartment fire framework that predicts the fire development in conventional compartments.This comparison highlights the limitations of this framework, and the subsequent analysis proposes several changes to include the effect of burning timber elements. It is concluded that gas flow velocities increase with the amount of timber present in the compartment. Therefore, the fire transitions to a new regime where the gases do not have enough time to mix and react inside the compartment, the temperatures decrease and the horizontal velocities at the opening increase.

Ventilation effects on the thermal characteristics of fire spread modes in open-plan compartment fires

Our understanding of fire behaviour and heating conditions for load-bearing structural elements was developed from an immense body of research in small under-ventilated compartment fires. Within the context of contemporary architecture, large open-plan compartments are commonplace, yet understanding of the first principles that define fire behaviour in such enclosures remains limited. Past experiments have revealed that fires in open-plan compartments exhibit three distinct fire spread modes: a fully-developed fire, a growing fire, and a travelling fire. This paper studies the thermal characteristics arising from these fire spread modes and the effects of the ventilation imposed. An experimental analysis of the energy distribution and spatial heating is conducted on a series of large-scale compartment fire tests, with the fire spread mode and ventilation conditions systematically varied. Each fire spread mode is shown to induce significant and characteristic spatial heat distributions. Moreover, the analysis of the ventilation modes shows equivalent thermal loads imposed on the structure in cases where the opening areas are large, and plume flows are dominant despite lower gas temperatures and irradiation. Thus, fires in open-plan compartments pose unique and possibly more severe thermal loading to structural systems, a characteristic not captured by current design fire methodologies.

Conceptual framework for quantifying fire resilience – A new perspective on fire safety performance of buildings

A conceptual framework for quantifying fire resilience, a new perspective on fire safety performance of buildings, is presented. Fire resilience is a measure suitable for evaluating fire safety performance of buildings whose functional continuity is required even after a fire. In this study, fire resilience was formulated as a function of the recovery time of internal spaces as a function of the extent and degree of fire damage. Possible fire scenarios for the considered buildings were determined via an event-tree approach in which the fire behavior of each fire compartment was estimated using existing engineering correlations. The obtained fire behavior was further transformed into the recovery time based on the recent statistics from Japan. The evaluation procedure was applied to an office building as a case study. Among the design specifications tested, installation of a sprinkler system was the most effective in enhancing the fire resilience.

Semi-empirical model for estimating the heat release rate required for flashover in compartments with thermally-thin boundaries and ultra-fast fires

More than 1 billion people are living in informal settlements and refugee camps where houses are commonly built from thermally-thin materials (e.g. steel/asbestos sheets). In fire safety literature there is insufficient attention describing the required conditions for flashover (e.g. Heat Release Rate needed for flashoverQ˙FO) in such compartments. In this work, Q˙FO and heat fluxes to the surroundings for compartments with thermally-thin boundaries were investigated using eight compartment fire tests built with 0.5 mm steel sheets and four fuel loads. Numerical simulations were conducted to validate FDS for this application, using the heat release rate inside and outside the compartment, the gas layer temperature and the heat fluxes to the surroundings. The validated model was employed to conduct demonstrative sensitivity and parametric studies to understand the heat balance for thermally-thin under-ventilated compartments. It was found that the heat transfer on/from the walls of the compartment is dominated by radiation, in contrast to the compartments with thermally thick boundaries where the wall conduction dominates. The radiative heat transfer coefficient hrad was then resolved numerically and correlated against the gas layer temperature, wall temperatures and the Q˙FO to create a semi empirical correlation for estimating the Q˙FO.

A full-scale experimental study on single dwelling burning behavior of informal settlement

Approximately one billion people globally live in informal settlements with a large potential fire risk, where a single dwelling fire may result in a very large urban conflagration leaving hundreds, if not thousands, of people homeless. What is not well understood, however, is how fires in informal settlement dwellings develop and spread, and what influence the dwelling boundary has on these two areas. In this work, four different real-scale compartments were constructed and ignited under a large fire calorimeter hood. The cases include a typical thin metal-walled dwelling (baseline), a no leakage dwelling, a dwelling lined with cardboard and a dwelling with highly insulated walls. The fuel locations, fuel loads of 25 kg/m2, ignition method and ambient conditions were kept identical in four experiments. Important parameters of compartment fire development, such as heat release rate, gas temperatures, fuel mass loss rate, wall and ceiling temperature were recorded. To investigate the fire spread mechanism between dwellings, the incident radiation heat flux around the dwellings and projection flame length were measured as well. It was found that the boundary conditions in informal settlement significantly affect the fire dynamics and fire spread of informal settlement, and that current analytical/empirical equations are not capturing accurately experimental observations.

High-temperature steady-state experiments on G550 cold-formed steel during heating and cooling stages

Steel structures usually experience heating and cooling stages during a compartment fire. Most previous investigations on the high-temperature material properties of cold-formed steel (CFS) focused on the heating stage of steel, corresponding to the growth and fully developed phases of a compartment fire. The influence of the cooling stage of steel, which corresponds to the decay phase of a compartment fire, has not been properly considered. This study conducted 88 steady-state tests on G550 CFS at elevated temperatures and investigated the material properties during the heating and cooling stages. The results show that the prediction of the time-dependent load-bearing capacity of CFS structures under compartment fires might become non-conservative if the material properties of the G550 CFS during the cooling stage are replaced with those during the heating stage. For instance, when the tensile temperature is less than 500 °C and the peak temperature is greater than or equal to 600 °C, the yield strength reduction factors of G550 CFS during the cooling stage are significantly lower than those during the heating stage under the same tensile temperature. In addition, the distribution of the yield strength (ultimate strength) reduction factors of G550 CFS during the cooling stage is affected by the peak and tensile temperatures and displays two branches. The difference in the reduction factors between the two branches is significant under the same tensile temperature and different peak temperatures. Finally, unified equations for the material property reduction factors and stress–strain curves are proposed and can provide a reasonable prediction of the material properties of G550 CFS under full-range compartment fires. • Steady-state tests of CFS were conducted during heating and cooling stages. • The difference in the test results during heating and cooling stages is significant. • The distribution of yield strength curves during the cooling stage displays two branches. • The prediction of the bearing capacity of CFS structures in fires might become non-conservative. • Expressions are provided for the material properties of G550 CFS under full-range fire.

Incorporation of elevator evacuation from a specific floor – A numerical study of an office building

This paper investigates evacuation from a specific floor plan to determine if elevators can replace one of the escape routes consisting of a staircase without lengthening the evacuation times. This study specifically studies evacuation from one single office floor with 360 and 540 occupants, designed as one fire compartment with an area of 2800 m2. To specify the occupants’ willingness to use the elevator for evacuation from different floors, three different functions are used. These functions are modified to include more floors and are used to derive different distributions for the proportion using staircases and elevators, by simulations in Pathfinder. Two setups are studied. First, three staircases are used for evacuation. Secondly, one staircase is replaced with five evacuation elevators with capacity for eight occupants, and one elevator for sixteen occupants. For these setups, evacuation is studied from the 2nd, 8th, 16th, 25th and 50th floor. In addition to the studied functions, distributions that minimize the evacuation time for each floor are derived from the simulations. These distributions give the shortest possible evacuation times. The distributions are then compared to evacuation simulations from the first setup, only utilizing the three staircases. The results show that for the elevators to fully replace a staircase, between 45-60 % of the floor occupants need to use the elevators when the occupant count is 360, and 43-50 % when the number of occupants is 540. However, these values are dependent on floor number. Compared to the functions studied, the optimal percentage is significantly higher for lower floors, becoming closer to the functions as they increase with higher floor numbers. For each distribution on every floor, queuing time was also studied. Based on the results from the calculations, the study concludes that six evacuation elevators could replace one staircase on the studied office floor. However, this result relies on a certain percentage of the occupants using elevators for evacuation.

Behavior and Limit States of Long-Span Composite Floor Beams with Simple Shear Connections Subject to Compartment Fires: Experimental Evaluation

This paper presents the results of compartment fire experiments on four 12.8 m long composite floor beams with various end support conditions. Specimens were constructed as partially-composite beams, consisting of W18×35 steel beams and 83 mm thick lightweight concrete slabs cast on top of 76 mm deep ribbed steel deck units. Test variables included two types of simple shear connections (shear-tab and welded-bolted double-angle connections) and the presence or absence of slab continuity over the girders. Each specimen was subjected to gravity loading using hydraulic actuators and 4000 kW compartment fires produced using natural gas-fueled burners. This study evaluated the characteristics of the fire loading and thermal and structural responses of the specimens. The test results indicated that there were significant effects of thermal restraints on the behavior and failure modes of the specimens with simple shear connections. The specimens resisted gravity loads at large vertical displacements near midspan (approximately a ratio of span length over 20) without collapse under fire loading. However, various limit states and vulnerabilities to fires were observed, including local buckling of steel beams near supports, flexural failure (yielding of steel beams and concrete fracture near restrained end supports), and connection failure (weld shear or bolt shear) during heating and cooling which could lead to partial or total collapse of the floor system.

3D Mapping of the Sprinkler Activation Time

Sprinkler activation is one of the key events defining the course of a compartment fire. The time when activation occurs is commonly used in the determination of the design fire scenario, which is the cornerstone of the design of building fire safety features. A well-known model of sprinkler activation (response time index (RTI) model) was introduced into the numerical scheme of the ANSYS Fluent computational fluid dynamics (CFD) package. The novel way in which the model is used is the calculation of the time for sprinkler activation within each discrete cell of the domain. The proposed novel approach was used in a case-study to assess the effects of comfort mode natural ventilation on a sprinkler’s activation pattern. It was found that hinged vents in the comfort mode had a significant effect on sprinkler activation, both in terms of delaying it as well as limiting the total number of cells in which the sprinkler would have activated. In some scenarios with a hinged vent, no activation was observed in the central point of the vent, possibly indicating problems with the autonomous triggering of the fire mode of such a device. It was also found that the RTI and C (related to the conductive transport of sprinkler fitting) parameter values had a moderate influence on sprinkler activation time—only for high-temperature sprinklers (≥ 141 °C). This study shows the applicability of the 3D activation time mapping for research focused on the fire safety of sprinkler-protected compartments and for the performance-based approach to sprinkler system design. Even though the RTI model is the industry standard for the determination of sprinkler response, the model implementation in ANSYS Fluent was not validated. This means that sources of uncertainty, mainly connected with the determination of flow velocity and temperature are not known, and the model should be used with caution. An in-depth validation is planned for subsequent studies.