Equivalent Fire Research Articles

Flexural behaviour and shear capacity of RC flat plate sections during fire exposure

PurposeFire safety is a pivotal requirement in building codes. Prescribed design criteria have been the norm to achieve it, which imposes limitations on engineers, including the inability to accommodate new solutions/materials. The shift towards performance-based design offers the potential to address shortcomings of the prescribed design. However, this shift also significantly increases the workload on structural engineers without a corresponding increase in their engineering fees. Simplified design tools are needed to assist engineers in this transition.Design/methodology/approachThe paper is divided into sections investigating equivalent standard fire duration, thermal deformations, flexural behaviour and shear capacity of flat slabs when exposed to fire. The first section conducts a parametric study correlating equivalent and realistic fire durations using the average internal temperature profile (AITP) method, resulting in statistical equations estimating equivalent fire duration. The second section evaluates thermal deformations and flexural behaviour through a parametric study considering various parameters. This section results in statistical equations estimating thermal deformations and flexural behaviour of flat slab sections during fire exposure. The final section focuses on shear capacity, developing simplified heat transfer formulas and statistical equations predicting compression zone depth reduction. The section presents methodologies predicting flat slab sections' one-way and two-way shear capacities during fire exposure.FindingsStructural engineers can use the proposed methods for daily design work without applying complex heat transfer calculations. When the equivalent standard fire duration is utilized, a flat slab’s thermal deformations, flexural behaviour and shear capacity under an actual fire condition can be calculated. As such, the methods would be highly beneficial in assessing the structural integrity of a building during an active fire incident.Originality/valueThe paper provides engineers with the tools required to evaluate the safety of flat slab sections during fire exposure. The methodologies presented in the paper enable engineers to use performance-based design for slab sections by (1) converting any real fire scenario to a standard fire with an equivalent duration, (2) assessing their thermal behaviour, (3) evaluating their flexural behaviour and (4) evaluating their flexural and shear capacities. The paper concludes with a case study example demonstrating the detailed application of the developed methods.

Study on the Configuration and Fire-Resistant Property of Cable Tunnel Fireproof Clapboard Based on Equivalent Fire Condition Testing

At present, the selection criteria and configuration methods for fireproof clapboards in cable tunnels are not yet perfect, making it difficult to achieve effective fire protection. Therefore, an equivalent fire condition testing method is proposed to analyze the fire-resistant property of fireproof clapboards of different materials. Firstly, a tunnel fire experiment platform was built to carry out the combustion experiment of the high-voltage cable intermediate joint. The cable combustion equivalent fire source device is developed based on the temperature rise characteristics under different combustion conditions. However, the temperature rise characteristics of the equivalent fire source and the actual cable combustion error are within 10%. Then, four typical fireproof clapboards were tested under equivalent fire sources. The results indicate that the organic molded board has the best performance. In addition, factors such as the thickness, side panel height, and installation method of the fireproof clapboards were tested and analyzed. The results indicate that a minimum thickness of 5 mm for the fireproof clapboard and a height of 200 mm for the side panel of the clapboard are necessary to ensure effective protection. The installation method of hoisting fireproof clapboards can effectively extend the protection time by about 30% compared to the flat method.

Quantitative assessment of the extent of damage to timber structures during the full course of a real fire using the energy equivalence method

In this study, an innovative method, the Energy Equivalence Method (EEM), is proposed in the context of the Performance-Based Fire Engineering (PBFE) framework for quantitatively assessing the degree of damage of timber structures during the full process of a real fire. To verify the validity of the method, glued laminated timber (GLT) specimens and GLT columns were selected as the subjects of fire action, and a series of equivalent fire experiments were conducted by using a parametric fire model (referred to as the DNI fire model), which is currently used in Germany, to simulate real fire scenarios. By comparing the equivalence of charring depth (CD), pyrolysis zone temperature, and residual load-carrying capacity of the test specimens after the action of the DNI fire and its equivalent standard fire, the validity of the EEM in quantifying the degree of damage to timber members after the DNI fire was fully verified. Subsequently, based on the fire experimental data, accurate thermal and structural models were developed, and these models were utilized to further validate the effectiveness of the EEM in quantifying the extent of damage to timber members under the action of a DNI fire over an arbitrary time period. The results of the study show that the proposed EEM not only can be used to assess the extent of structural damage during fire action and the residual load carrying capacity of the structure after fire action, but also promotes the transition from standard fire safety design to the PBFE design.

Study on Fire Load and Duration of Fire in Logistics Facilities

Logistics facilities differ significantly from general buildings in terms of diffusion flame prevention technology, necessitating the application of fire diffusion prevention technology. The total fire load in a fire compartmentation was calculated according to the method presented in The NFPA (The National Fire Protection Association) Fire Protection Handbook, based on the results of a survey on the area, height, and rack dimensions of 29 logistics warehouses in Korea to improve the fire compartmentation standard. In addition, simulations were conducted using CFAST (Consolidated Fire and Smoke Transport) for the cross-validation of these methodologies. Through fire simulations, the temperature of the upper part of each fire compartment was derived, and the equivalent fire duration was calculated by converting it to an area based on the standard time-heating temperature curve of KSF 2257-1. The NFPA methodology and values calculated through fire simulations showed similar results. In addition, we analyzed the tendency of the equivalent fire duration according to the height of the fire compartmentation and confirmed that the higher the floor height, the higher the equivalent fire duration. The results of this study can be used as basic data for improving the fire prevention standards by calculating the equivalent fire duration according to the fire load of a logistics facility and for confirming the tendency of the equivalent fire duration according to the height of the fire compartment.

Simple Estimates of the Most Adverse Fire Growth and Equivalent Fire Severity in Concrete Compartments for Structural Safety

Simple Estimates of the Most Adverse Fire Growth and Equivalent Fire Severity in Concrete Compartments for Structural Safety

Experimental and numerical study on the validity of the energy-based time equivalent method for evaluating the fire resistance of timber components exposed to travelling fires

An energy-based time equivalent method that is capable of converting the fire resistance design of timber components exposed to the realistic fire to that of the standard fire was proposed. To verify the effectiveness of the method applied to the improved Travelling Fires Methodology (iTFM) fires, a series of iTFM fires and their corresponding equivalent standard fire tests were implemented on six glued laminated timber columns. The effectiveness of the method was fully confirmed by comparing the fire effects, the temperature distribution of the pyrolysis layer, and the remaining load-bearing capacity after fire for the timber columns under the iTFM fires and their equivalent standard fires. Meanwhile, it was well illustrated that the adhesive layer was almost no effect on the fire resistance of the timber columns by comparing the cross-sectional temperature distribution, charring depth and charring rate in two directions of the timber columns. To simplify the application of the energy equivalence method, the thermal properties relationships applied to the finite element heat transfer analysis of timber were modified. The accuracy of the modified thermal property relationships was demonstrated by comparing the surface temperature, charring depth, and charring rate obtained from finite element simulations with those measured by the experiment. The simplified energy equivalence method based on the finite element was not only easy for designers to apply, but also helped to promote the development of performance-based fire protection design for timber structures.

Report on Existing Fireproof Construction Guidelines for Dwellings against Wildfires

This work presents a state-of-the-art review of existing fireproof construction guidelines for dwellings against wildfires. The most important wildfire-proof construction guidelines and codes for dwellings are presented, and these are later associated with existing fire engineering chapters associated with building codes. It was concluded that the variability in this subject is very high, and the approach to classifying the thermal effects in construction still lags behind scientific consensus. Moreover, the constructive requirements depend severally on the country’s building code when assessing the fireproof requirements for wildfire. Moreover, the thermal actions of wildfires in dwellings are presented and compared with classical ISO-834 standard fire curves, in which the maximum equivalent fire exposure time can range from 2 to 4 h depending on the country’s code. The key contributions of this work consist of (i) thoroughly disseminating codes and guidelines to promote scientific discussion in order to advance the wildfire fireproof standards dedicated to WUI; (ii) emphasizing the void in current codes in order to promote conversation between future researchers.

Investigation of the maximum tunnel ceiling temperature caused by two fires

This paper investigated the maximum ceiling temperature and equivalent single fire source induced by two fires combined with small-scale experimental data and numerical simulations. The influences of fire size and spacing on the maximum temperature expressed by the heat release rate (HRR) for two fires were considered. The results demonstrate that the experimental maximum temperatures in the tunnel are smaller than those obtained by Li's model. Accordingly, a model to describe the maximum temperature for two fires expressed by the HRR was proposed, and the change trend of the HRR ratio was analyzed. The predicted values agree well with the experimental and numerical values, verifying that the proposed model is reliable.

Experimental Evaluation of Fire Resistance Limits for Steel Constructions with Fire-Retardant Coatings at Various Fire Conditions

The experimental evaluation of fire resistance limits for steel constructions with fire-retardant coatings consists of a lot of experiments on the heating of steel structures of buildings by solving a heat engineering problem at various fire conditions. Building design implies the assessment of compliance of actual fire resistance limits for steel constructions with the required limits. Fire resistance limits for steel constructions are determined for “standard” temperature mode, and this can lead to overestimated fire resistance and underestimated heat influence for a real fire. Estimation of the convergence for “standard” temperature mode and possible “real” fire mode, as well as of the compliance of actual fire resistance limits with real fire conditions, was realized in the following stages: mathematical modeling of real fire development by the field model in software package Fire Dynamics Simulation (FDS) with various fire loads and mathematical modeling of steel construction heating for the standard temperature mode obtained by modeling “real” fire modes (the finite difference method of solving the Fourier heat conduction equation at external and internal nonlinearities was used for modeling the process of steel structure heating with the implementation in the ANSYS mechanical software package). Experiments of the assessment of fire-protective paint’s effectiveness were carried out for standard temperature mode and obtained by modeling “real” fire modes. The equivalent fire duration dependence on fire load type was determined. This dependence can be taken into account in determination of fire resistance limits for steel constructions in warehouse building roofing. Fire-protective paint effectiveness was estimated for “standard” temperature mode and various other temperature modes.

Fire dynamics inside a large and open‐plan compartment with exposed timber ceiling and columns: CodeRed #01

SummaryThere is an increasing global demand to build from timber as it is a sustainable and attractive material. One of the key challenges associated with timber buildings is their performance in a fire, in particular, for medium‐ and high‐rise buildings and when timber is exposed. Research on this topic to date has been performed in compartments smaller than 84 m2 which does not capture the fire dynamics of large compartments. This paper presents the first in a series of experiments carried out inside a large, purpose‐built, open‐plan compartment with a floor area of 352 m2. The large‐scale compartment had a fully exposed, unloaded, cross‐laminated timber (CLT) ceiling and glued laminated timber (glulam) columns, made with adhesives that have been tested to not exhibit char fall‐off in fire. At 352 m2 floor area, this is currently the largest compartment fire experiment carried out globally. The compartment characteristics and the arrangement of the wood crib mimicked the previous series of experiments in Poland in a non‐combustible compartment by Rackauskaite et al. (2021). The experiment was instrumented with thermocouples measuring the gas temperature in the compartment, and above two of the openings, as well as the temperature within the timber members. Plate thermometers were also included to measure the heat flux to the ceiling and of the external flaming. Additionally, fixed and drone‐mounted cameras captured the fire. A protected steel column was added to calculate the equivalent fire exposure when compared to a standard fire resistance furnace test. The experiment was allowed to burn out without fire‐fighting intervention. Continuous measurements were taken for 48 h. The wood crib was ignited at one end of the compartment. Flames rapidly spread across the timber ceiling to the other end of the compartment with the rest of the wood crib being involved in the fire at 5 min 36 s from ignition. The total duration of the fire was 22 min 30 s, at which time visible flaming ceased. Significant external flaming was observed through the openings in the order of 3 m in height but varied with position as the fire travelled across the compartment. Analysis of the experimental results and camera footage showed that the presence of the timber structure approximately doubled the heat release rate (HRR) compared to the value expected from the wood crib alone. Smouldering combustion of the timber members continued for hours after the cessation of flaming, burning in several hotspots, resulting in holes through the CLT slab. This paper improves the understanding fire dynamics for open‐plan, exposed timber compartments and has shown that issues such as external flaming, smouldering and the increase in HRR need to be considered when deriving practical design solutions.

An improved theoretical model for the maximum smoke temperature rise in a tunnel based on equivalent fire source

The maximum smoke temperature rise underneath tunnel ceiling is of great importance for the assessment of heat exposure, estimation of fire detection time and possibility analysis of fire spread. Previous studies mainly focused on the scenario with a single fire source, but the existence of two fire sources is common due to the increase traffic volume. The maximum smoke temperature rise induced by two fire sources is studied through theoretical analysis in this study. A virtual equivalent fire source is proposed, which is mainly affected by the total fire heat release rate (HRR) of two fires, longitudinal ventilation velocity, effective tunnel height and separating distance between two fires. The HRR of the equivalent fire source decreases with a longer separating distance, which indicates that the influences of the downstream fire on the maximum ceiling temperature weakens gradually as the separating distance increases. An improved model on the maximum ceiling smoke temperature rise caused by two fire sources was developed, and the predictions based on the revised model agree well with the experimental data.

The calculation of required fire resistance limits for engineering structures of technological pipe racks at oil and gas processing plants on the basis of an evaluation of the time needed for personnel evacuation and rescue in case of fire

Introduction. GOST R 12.3.047-2012 standard offers a methodology for determination of required fire resistance limits of engineering structures. This methodology is based on a comparison of values of the fire resistance limit and the equivalent fire duration. However, in practice incidents occur when, in absence of regulatory fire resistance requirements, a facility owner, who has relaxed the fire resistance requirements prescribed by GOST R 12.3.047–2012, is ready to accept its potential loss in fire for economic reasons. In this case, one can apply the probability of safe evacuation and rescue to compare distributions of fire resistance limits, on the one hand, and evacuation and rescue time, on the other hand.A methodology for the identification of required fire resistance limits. The probabilistic method for the identification of required fire resistance limits, published in work [1], was tested in this study. This method differs from the one specified in GOST R 12.3.047-2012. The method is based on a comparison of distributions of such random values, as the estimated time of evacuation or rescue in case of fire at a production facility and fire resistance limits for engineering structures.Calculations of required fire resistance limits. This article presents a case of application of the proposed method to the rescue of people using the results of full-scale experiments, involving a real pipe rack at a gas processing plant [2].Conclusions. The required fire resistance limits for pipe rack structures of a gas processing plant were identified. The calculations took account of the time needed to evacuate and rescue the personnel, as well as the pre-set reliability of structures, given that the personnel evacuation and rescue time in case of fire is identified in an experiment.

Energy‐based time equivalent approach for evaluating the fire resistance of timber components exposed to realistic design fire curves

SummaryAccording to the concept of performance‐based design, the fire safety design of the timber structures should be focused on the actual design fire, which represents the realistic fire situation in a given building. However, the current prescriptive only provides a method for evaluating the fire resistance of timber components under standard fire. This paper proposed an energy‐based time equivalent approach (EBTEA) for evaluating the fire resistance of the timber components in realistic design fire scenarios. As an alternative, this method was based on the principle of energy equivalence so that the fire resistance design of timber components exposed to realistic fires was standardized, which can make fire resistance rating database available under standard fire exposure and promote performance‐based design. The validity of the method was verified by comparing the predicted values of EBTEA with the existing values obtained from the nonlinear finite element analysis. The proposed method was further simplified by analyzing the key factors of energy equivalence and using nonlinear fitting methods to facilitate the use of designers. The simplified EBTEA can predict equivalent fire resistance of timber components under realistic design fire scenarios.

PDE solution to UAV/UGV trajectory planning problem by spatio-temporal estimation during wildfires

Unmanned Aerial Vehicles (UAVs) and Unmanned Ground Vehicles (UGVs) have been used in research and development community due to their strong potential in high-risk missions. One of the most important civilian implementations of UAV/UGV cooperative path planning is delivering medical or emergency supplies during disasters such as wildfires, the focus of this paper. However, wildfires themselves pose risk to the UAVs/UGVs and their paths should be planned to avert the risk as well as complete the mission. In this paper, wildfire growth is simulated using a coupled Partial Differential Equation (PDE) model, widely used in literature for modeling wildfires, in a grid environment with added process and measurement noise. Using principles of Proper Orthogonal Decomposition (POD), and with an appropriate choice of decomposition modes, a low-dimensional equivalent fire growth model is obtained for the deployment of the space–time Kalman Filtering (KF) paradigm for estimation of wildfires using simulated data. The KF paradigm is then used to estimate and predict the propagation of wildfire based on local data obtained from a camera mounted on the UAV. This information is then used to obtain a safe path for the UGV that needs to travel from an initial location to the final position while the UAV’s path is planned to gather information on wildfire. Path planning of both UAV and UGV is carried out using a PDE based method that allows incorporation of threats due to wildfire and other obstacles in the form of risk function. The results from numerical simulation are presented to validate the proposed estimation and path planning methods.

Performance-based design of RC beams using an equivalent standard fire

Purpose The design of buildings for fire events is essential to ensure occupant safety. Supplementary to simple prescriptive methods, performance-based fire design can be applied to achieve a greater level of safety and flexibility in design. To make performance-based fire design more accessible, a time-equivalent method can be used to approximate a given natural fire event using a single standard fire with a specific duration. Doing so allows for natural fire events to be linked to the wealth of existing data from the standard fire scenario. The purpose of this paper is to review and assess the application of an existing time-equivalent method in the performance-based design of reinforced concrete (RC) beams. Design/methodology/approach The assessment is established by computationally developing the moment-curvature response of RC beam sections during fire exposure. The sectional response due to natural fire and time equivalent fire are compared. Findings It is shown that the examined time equivalent method is able to predict the sectional response with suitable accuracy for performance-based design purposes. Originality/value The research is the first to provide a comprehensive evaluation of the moment-curvature diagram of RC beams using time-equivalent standard fire scenarios that model realistic fire scenarios.

Assessment Methods for Fire Durability of Intumescent Fire Protection Coatings

Fire durability of intumescent coatings is their ability to retain their fire-protective properties under fire conditions (under the influence of real temperature conditions of fire). The peculiarities of application of intumescent fire-protective coatings in single-storey buildings on the steel frame with account of fire load are considered. In this study, the fire hazard assessment of single-storey buildings on a steel frame with the use of sandwich panels as enclosing structures is made. The analysis of fire load values has been made. Numerical experiments on estimation of the indoor fire temperature regime have been carried out. For estimation of influence of temperature modes of fire on fire resistance of steel structures the software complex “Fire Dynamics Simulator” was used, which implements the field mathematical model. Various fire temperature modes (temperature-time dependencies) were obtained. Modelling of fire temperature modes was performed without taking into account active fire protection systems. The most critical and unfavourable by their consequences fire scenarios, used later for solving the heat engineering problem, have been chosen by experts. Numerical experiments on heating of steel structures were carried out by solving the heat engineering problem in conditions of non-stationary heat influence at standard temperature conditions according to ISO 834 and at fire temperature conditions obtained by modelling results. The estimation of equivalent fire duration on loss of bearing capacity for steel structures is made. ANSYS mechanical” computing complex was used for modelling the heating of steel structures, which allows us to perform heat engineering calculation of the structure on the basis of its software model.

Investigation of Fire Resistance Performance Considering Fire Conditions in Compartments

A fire resistance design has been applied for the safety of the structure in preparation for the fire that occurred in the building. However, there might be a limit to considering the various fire elements in the design. Particularly, for a natural fire curve, it is difficult to evaluate the structure's fire resistance performance through a full-scale fire test. Thus, the standard fire curve, developed based on time-temperature, has been used instead. In a bid to evaluate the fire resistance performance using the natural fire curve, the procedure proposing that the natural fire curve was first developed depending on the fire load and opening area through the fire test in the compartment, which is then equivalently substituted into the standard fire curve with the same fire load value, was proposed in this study. Heat transfer analysis was performed to verify whether the equivalent-substituted fire curve causes the same temperature gain as the natural fire curve. By comparing the two values, a significantly similar value was found around 20℃. Keywords: Fire Compartment Fire Test, Natural Fire Curve, Equivalent Fire Severity

Fire Damage Identification in RC Beams based on Support Vector Machines considering Vibration Test

In order to obtain the degree of damage in reinforced concrete (RC) beams exposed to fire, using the equivalent fire exposure time as the damage index, a new method of damage identification based on the support vector machine technology was proposed. Firstly, the feasibility analysis was conducted based on finite element models of simply supported beams. Thereafter, four RC simply supported beams were designed for fire test and vibration test, which were used to amend the finite element model and the SVM-based identification method. Fire tests were carried out on 4 beams for 60, 90, 120, and 150 min, respectively. During and after the fire tests, structural modal information were recorded. The first two order modal information, as SVM input paraments, was used to predict the equivalent fire exposure time based on SVM. The predicted results were very close to the actual fire exposure time. The residual bearing capacities of the beams after fire were calculated according to the predicted fire exposure time, which were close to experimental results. It indicated that the equivalent fire exposure time as the output parameter for damage identification was reliable. Finally, on the basis of damage identification method for simply supported beams, a new three-step positioning method was established for identifing the degree of damage in continuous beams. The method was applied to a thress-span continuous beam. The numercial situlation results revealed that the three-step positioning method was accurate.

МЕТОДЫ ОПРЕДЕЛЕНИЯ ТРЕБУЕМЫХ ПРЕДЕЛОВ ОГНЕСТОЙКОСТИ СТРОИТЕЛЬНЫХ КОНСТРУКЦИЙ ПРОИЗВОДСТВЕННЫХ ОБЪЕКТОВ

Introduction. In this study in accordance with the main principles of a probabilistic approach a method for a determination of required fire resistance limits of building structures of industrial objects was proposed. This method is based on a comparison of such random values as the fire resistance limits and the times required for an evacuation and a rescue. This method is particularly useful for external installation (for example pipe racks) of oil and gas plants. Methods. A new probabilistic method for a determination of required fire resistance limits of building structures of industrial objects is proposed, which differs from that presented in GOST R 12.3.047-2012. The method is based on a comparison of distribution functions for such random values as an evacuation time, a time required for a rescue and fire resistance limits and differs from the method described in GOST R 12.3.047-2012, in which an equivalent fire duration and the fire resistance limits are compared. The proposed method takes into account that an owner of the object can risk of his property at an undoubtedly execution of requirements of a safety of people in the case of the fire (both personnel and people living near the object). These requirements are stated in a common in the article 6 of the Federal law on 22.07.2008 No. 123-FZ “On a technical regulation of a fire safety in Russian Federation”. Results. The method was tested for the cases of the evacuation and the rescue of people. It was mentioned that for an application of the proposed method the following input data are required: the required reliability of the building structures, the evacuation time and its standard deviation of a distribution, the time required for the rescue and its standard deviation of a distribution, the standard deviation of a distribution of the fire resistance limit. Conclusion. In this study a new method for an evaluation of the required fire resistance limits of the building structures of industrial objects was proposed which is mostly applicable for the external technological installation (for example pipe racks) of oil and gas plants. The required reliability of the building structures is stated by a directive way. The evacuation time can be evaluated by the methods described in normative documents. But for other values either an analysis of statistical data is required (for the case of the standard deviation of the distribution of the fire resistance limit) or large scale experiments (the standard deviations of the distributions of the evacuation time and the time required for the rescue) should be performed.

О ФИЗИЧЕСКОМ СМЫСЛЕ И ОСНОВНЫХ ПОДХОДАХ К ОЦЕНКЕ ПОКАЗАТЕЛЯ "ЭКВИВАЛЕНТНАЯ ПРОДОЛЖИТЕЛЬНОСТЬ ПОЖАРА"

О ФИЗИЧЕСКОМ СМЫСЛЕ И ОСНОВНЫХ ПОДХОДАХ К ОЦЕНКЕ ПОКАЗАТЕЛЯ "ЭКВИВАЛЕНТНАЯ ПРОДОЛЖИТЕЛЬНОСТЬ ПОЖАРА"