Design Fire Curves Research Articles

Fire resistance of square concrete columns reinforced with GFRP bars, experimental and numerical investigation

Glass Fiber Reinforced Polymer (GFRP) materials have proven its efficiency in reinforcing concrete elements. The performance of Glass reinforced concrete columns (GRC columns) under axial loads have been studied well experimentally and numerically, While there are a very limited studies about the behavior of reinforced concrete GRC columns when exposed to fire. The weak performance of GFRP bars under fire compared to steel gave a warning about ignoring the fire behavior of GRC columns in fields. The fire performance of square GRC columns has been investigated experimentally and numerically in this study. The experimental program was done by testing nine GRC columns under design fire curve. All columns were tested under constant load during fire. Fire temperature was controlled to follow the design fire curve. Different parameters were investigated in this research; applied load ratio, concrete cover, and column configurations on the fire performance of GRC columns. Fire resistance (FR) of all tested columns were recorded and some recommendations about the FR of GRC columns were developed. The numerical study was conducted using the nonlinear finite element software. 3D-model using ABAQUS program was calibrated to reach the best simulation of GRC columns exposed to design or standard fire curve. The numerical study was done to extend the investigation of the experimental program. The influence of the various parameters have been examined to govern the fire performance of GRC columns. The experimental and numerical studies revealed that the fire resistance of GRC columns is highly affected by the applied load during fire. The difference between FR of GRC columns compared to steel-RC columns (SRC columns) was significant at eccentricity to width ratio greater than or equal to 0.2 and at higher applied load ratios. Spalling has a significant influence on the fire resistance and modes of failure of GRC columns.

Effect of different load levels on the flexure performance of RC beams exposed to fire

The paper presents the effect of different load ratios on the thermal and flexural behaviour of RC beams during and after fire. Full scale beam specimens of normal strength concrete of dimensions 230 mm × 400 mm × 4000 mm were exposed to design fire curves for the same duration under load ratios of 0.0, 0.20 and 0.40 of the ultimate load. Finally the beams were mechanically loaded till failure to estimate the residual capacity after cooling. The results showed that with the increase in the pre-load during fire alters (a) the thermal profile of the specimens (b) The performance of the beam specimens and (c) The ultimate capacity and flexural stiffness of the beam specimens after fire. A numerical model was also proposed to validate the experimentally obtained results..

DESIGN FIRE CURVE SELECTION OF SMALL SCALE POOL FIRES IN A SCALED METRO STATION

n-heptane pool fire was numerically and experimentally investigated in a 1:100 scaled metro station. Fire Dynamics Simulator (FDS v6.7.5) has been applied to investigate smoke and temperature distribution by implementing different design curves in the station. Experimental and numerical studies were performed for 10 ml n-heptane fuel under zero piston effect. To develop performance-based design and to obtain reliable fire simulation results for structures, reasonable input conditions are essential for numerical studies. The aim of the study is to select most suitable fire design curve and make the numerical study independent of the experimental results for small scale hydrocarbon pool fires. In this study, t2, tanh, Eurocode 1 (BS EN 1991-1-2), exponential, and quadratic fire curves were investigated and validated with experimental results. The numerical results obtained using FDS were validated with experimental data and good agreement was observed for all design fire curves except quadratic one. It was observed that the exponential design fire curve predicted more similarly to the experimental data over the fire duration including growth, fully developed and decay phases. Regardless of the experimental results, it was seen that the temperature distribution results obtained from the numerical study using exponential fire design curve and the radiation / turbulence parameters obtained from the literature were found to have an average of 5% difference with the experimental results. It was also seen that the t2 and tanh curves have acceptable differences of 6.92% and 9.02%, respectively, and the Eurocode HC is less suitable than the other curves with a difference of 12.17%. Therefore, it can be said that in small scale hydrocarbon pool fires, fire design can be done using exponential design curve.

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.

Effect of ignition heat source on design fire curve of polyethylene foam in a compartment fire

This study analyzed a design fire curve in accordance with of an ignition heat source in a compartment. For this purpose, a structure with a 1:3 reduced scale of the ISO 9705 room corner tester was fabricated using fireboard, and the time variant heat release rate was calculated according to the volume of a polyethylene foam combustible. To predict the design fire curve, the exponential equation proposed in a previous study was compared with the heat release rate measured in a fire experiment. The retard index, which is the main factor used to predicting the time required to reach the maximum heat release rate, decreased proportion to the ignition heat source. This relationship was presented in an empirical equation. Especially, the retard index decreased according to the size of the ignition heat source regardless of the volume of the polyethylene foam combustible. By establishing experimental data considering the type and change in the volume of combustibles, the findings of this study can be used to create improved design fire curve prediction models.

Numerical investigation of prediction performance of design fire curves for a tunnel fire

The prediction performance of design fire curves is numerically investigated for tunnel fire using the fire dynamics simulator (FDS). A large eddy simulation (LES) was adopted in the simulation of a previous 750 kW tunnel fire experiment. Based on the experimental heat release rate, t2-fire growth, quadratic and exponential design fire curves (DFCs) are mathematically constructed and adopted in the FDS simulation. The predictions of each DFCs are compared against the experimentally measured smoke temperature, smoke travel time, and carbon monoxide (CO) concentration. In addition, the prediction performance of the mixture fraction (MF) and mixing controlled fast chemistry (MCFC) combustion models, is compared. The simulation results of the MF and MCFC models are similar except for the CO concentration features. For the performance of the DFCs, t2-fire growth curve with the MF combustion model is the most effective combination, which demonstrated the most reasonable agreement with the experimental data.

Identification and characterization of design fires and particle emissions to be used in performance‐based fire design of nuclear facilities

SummaryCERN operates one of the most complex particle accelerator facilities in the world. Several different hazards, including fires, are present and need to be investigated and reduced to a tolerable level. Toward this goal, CERN aims at developing a catalog containing detailed fire dynamics descriptions of combustible items present in its facilities. This paper contributes to this catalog in two ways. First, through the development of a design fire calculator for electrical cabinets that allows the determination of potential design fire curves for any number of electrical cabinets/racks. The second contribution was to experimentally characterize the smoke production rates and smoke particle properties of the most common cables and insulating oils used at CERN by coupling a fast particle mobility analyzer to a cone calorimeter. The two particle size modes (accumulation and nucleation mode) could be linked to the fire properties and heat release rate. Accumulation mode particles (~200 nm) were associated with high heat release rates and high soot emissions from the flame. This study identifies a necessity to consider ultrafine particle emissions with low mass emissions but high number emissions in relation to risk assessments pertaining to nuclear facilities and dispersion of radioactive aerosols to the surrounding environment.

Evaluation of Design Fire Curves for Single Combustibles in a Cinema Complex

An actual fire test was performed on single combustibles placed in a local cinema complex, and quantitative differences in the maximum heat release rate (HRR) and fire growth rate were investigated based on the design fire curve methods (i.e., the general and 2-stage methods). In terms of combustible use and fire load, a total of 12 combustibles were selected, classified into cinema lounge and movie theater. It was found that the maximum HRR and fire growth rate determined using the two-stage method were quantitatively different from those of the general method. The application of the two-stage method, which can be used to determine the fire growth rate of the initial fire stage more precisely, could be useful in accurately predicting the activation time of fire detectors and fire-extinguishing facilities, as well as the available safe egress time (ASET) and required safe egress time (RSET).

Framework for rapid prediction of fire-induced heat flux on concrete tunnel liners with curved ceilings

Recent vehicular fires in concrete-lined tunnels have demonstrated the vulnerability of the liner to heat-induced spalling and cracking damage. To evaluate the structural fire resistance of either existing or newly designed tunnel structures, there is a need for fast-running tools that can accurately predict the distribution and severity of fire-induced heat exposure over the interior surface of the liner. This study proposes an analytical prediction framework which is more realistic than current design fire curves and yet less computationally intensive than high-fidelity numerical solutions. The Confined Discretized Solid Flame (CDSF) model is proposed for calculating the spatial contour of total heat flux imparted to the tunnel liner due to an enclosed fire. The CDSF computation includes both radiation heat transfer via a 3D discretized solid flame and a convective region representing the ceiling jet of smoke and hot gas. CDSF heat flux results show strong agreement with experimentally validated computational models at a fraction of the computational cost over a matrix of four large vehicle fire sizes and three tunnel prototypes with curved ceilings (i.e. horseshoe or circular cross-sections). The fast-running CDSF approach is conducive to parametric thermal analysis and stochastic damage evaluation for concrete tunnel liners exposed to fire.

Thermal performance of non-load-bearing cold-formed steel walls under different design fire conditions

Most previous fire experiments of cold-formed steel (CFS) walls focused on the ISO 834 or the E119 fire curve. Although the fire performance of CFS walls under ISO 834 or E119 curve can be theoretically converted to that under other fire curves, the corresponding time equivalency methods have not been experimentally examined. This paper presents an experimental investigation of non-load-bearing CFS walls under four different fire conditions. It is proved by the experiments that the maximum temperature of the design fire curve is one of the most important indexes for representing the severity of fire exposure. Especially, the maximum temperature of 680 °C for external fire was not severe to the present non-load-bearing CFS walls. Two specimens were subjected to 285 min of external fire but demonstrated an almost steady-state heat transfer process. Meanwhile, the hydrocarbon fire and realistic design fire demonstrated much more severe damage. It is also proved for the first time that neither the equal area method nor the energy-based method was suitable for the fire-resistance time equivalency of CFS walls. Based on post fire observation, significant local crushing of studs was identified, especially after the fall off of fire-side sheathing. Additionally, it was found that replacing the fire-side base-layer gypsum plasterboard with low-bulk-density calcium-silicate board extends the insulation and structure performance of CFS walls under fire conditions. Moreover, a simplified temperature distribution model and the critical temperature on the fall off of fire-side gypsum plasterboard were recommended for the numerical modeling of CFS walls.

Evaluation of the Prediction Performance of Design Fire Curves for Solid Fuel Fire in a Building Space

Evaluation of the Prediction Performance of Design Fire Curves for Solid Fuel Fire in a Building Space

Evaluation of Design Fire Curves for Gas Fires in a Compartment Using CFAST

Evaluation of Design Fire Curves for Gas Fires in a Compartment Using CFAST

Evaluation of Modified Design Fire Curves for Liquid Pool Fires Using the FDS and CFAST

본 연구에서는 화재 시뮬레이션에 사용하기 위해 제안된 기존의 디자인 화재곡선을 일부 수정한 디자인 화재곡선을 제안하였다. ISO 9705 구획실 내 형성된 헵탄과 옥탄 풀화재를 대상으로 기존에 제안된 1-stage 디자인 화재곡선과 수정된 2-stage 디자인 화재곡선을 입력조건으로 적용하여 FDS와 CFAST를 이용한 시뮬레이션을 수행하고 실험결과와 비교하였다. FDS와 CFAST 시뮬레이션 결과에서 온도와 O2, CO2 농도에 대해서 전체적으로 2-stage 디자인화재곡선이 1-stage 디자인 화재곡선보다 잘 예측하였으며, 특히 화재 초기 성장단계에서 온도에 대한 예측은 2-stage디자인 화재곡선의 결과가 더 합리적임을 확인하였다. 구획실 내 온도변화에 대한 FDS와 CFAST 시뮬레이션 결과는상층부에 대해서는 비교적 합리적으로 예측하였고 두 계산결과에 차이가 크지 않았지만 하층부에 대해서는 두 계산모두 너무 낮게 예측하였으며 두 계산결과에도 차이가 크게 나타나는 것을 알 수 있었다.In this study, the previous design fire curve for fire simulation was modified and re-suggested. Numerical simulations withthe FDS and CFAST were performed for the n-heptane and n-octane pool fires in the ISO 9705 compartment to evaluate theprediction performances of the previous 1-stage and modified 2-stage design fire curves. The numerical results were comparedwith the experimental temperature and concentrations of O2 and CO2. The FDS and CFAST simulations with the 2-stage designfire curve showed better prediction performance for the variation of temperature and major species concentration than thesimulations with 1-stage design fire curve. Especially, the simulations with the 2-stage design fire curve agreed with theexperimental temperature more reasonably than the results with the 1-stage design fire curve. The FDS and CFAST simulationsshowed good prediction performance for the temperature in the upper layer of compartment and the results with the FDS andCFAST were similar to each other. However, the FDS and CFAST showed poor and different prediction performance for thetemperature in the lower layer of compartment.

Application Study of Design Fire Curves for Liquid Pool Fires in a Compartment

Application Study of Design Fire Curves for Liquid Pool Fires in a Compartment

Fire performance of LSF walls made of hollow flange channel studs

PurposeThis paper aims to present an investigation conducted to evaluate the effects of important parameters affecting the structural fire performance of light gauge steel frame (LSF) walls. It also evaluates the applicability of commonly used critical hot flange temperature method to determine the fire resistance ratings (FRR) of different LSF walls.Design/methodology/approachThe effects of important parameters such as stud section profiles and their dimensions, elevated temperature mechanical property reduction factors of the steel used, types of wall configurations and fire curves on the FRR of LSF walls were investigated. An extensive finite element analysis-based parametric study was conducted to evaluate their effects (finite element analysis – FEA). For this purpose, finite element models which were validated using the full-scale fire test results were used. Using the structural capacities obtained from FEAs, the load ratio versus FRR curves were produced for all the different LSF walls considered.FindingsStud depth and thickness significantly affected the fire performance of LSF walls because of the differences in temperature development pattern, thermal bowing deflections and the failure modes of stud. The FRR of LSF walls increased significantly when steel studs with higher elevated temperature mechanical property reduction factors were used. FRR significantly changed when realistic design fire curves were used instead of the standard fire curve. Furthermore, both the critical hot and average flange temperature methods were found to be unsuitable to predict the FRR of LSF walls.Originality/valueThe developed comprehensive fire performance data would facilitate the development of LSF walls with enhanced fire performance, and, importantly, it would facilitate and advance the successful applications of hollow flange channel section studs in LSF walls.

Energy-based time equivalent approach to determine the fire resistance ratings of light gauge steel frame walls exposed to realistic design fire curves

PurposeThis paper aims to present the details of a study undertaken to develop an energy-based time equivalent approach to obtain the fire resistance ratings (FRRs) of light gauge steel frame (LSF) walls exposed to realistic design fire curves.Design/methodology/approachThe energy-based time equivalent method was developed based on the performance of a structural member exposed to a realistic design fire curve in comparison to that of the standard fire time – temperature curve. The FRR predicted by the energy-based method for LSF wall configurations exposed to both rapid and prolonged fires were compared with those from fire design rules and finite element analyses (FEA).FindingsThe proposed energy method can be used to obtain the FRR of LSF walls in case of prolonged fires and cannot be used for rapid fires as the computed FRRs were higher than the results from FEA and fire design rules due to the influence of thermal bowing and its magnification effects at a high temperature gradient across the studs for rapid fires.Originality/valueThe energy-based time equivalent method was developed based on equal fire severity principles. Three different wall configurations were considered and exposed to both rapid and prolonged fires. The FRR obtained from the energy-based method were compared with fire design rules and FEA results to assess the use of the energy-based method to predict the FRR of LSF walls.

Development of objective-criteria-scenario triplets and design fires for performance-based Fire Safety Design

Detailed guidance for conducting performance-based fire engineering analyses for the built environment is lacking, in particular for how to identify and specify performance-criteria, fire scenarios and design fires. To help fill this gap, a method is proposed for establishing sets of ‘objective-criteria-scenario’ triplets and design-basis fires for different building-occupant systems, which can be used in regulation or directly by engineers. Application of the method forces the user to identify fire safety objectives for specific targets within a building, measurable performance criteria related to the targets and the objectives, detailed fire scenarios, and representative design fire curves, which are used to assess the building fire safety systems performance in meeting fire safety objectives. The method is briefly overviewed and particular emphasis is given to how historical data and experimental fire test data can be used to develop scenarios and associated design fire curves.

Performance-based fire behaviour analysis for underground parking structures

ABSTRACTThe current design code for building structures in South Korea specifies the minimum fire resistance ratings and fire-resisting performances for each structural component, for which a standard fire curve is required to be applied. There are, however, obvious differences between the standard fire curve and the actual fire behaviour observed from real events. In this study, a fire dynamic-based simulation was conducted on a typical underground parking structure, from which a realistic fire design curve was obtained. In addition, thermal behaviour and fire-resisting response of hollow-core slabs in the underground parking structure were estimated by using the realistic fire design curve, which was compared to those based on the design fire curve specified in the current code. On this basis, it is considered that more rational and economic fire resistance design of underground parking structure is possible by utilizing the realistic fire curve.

Fire design rules for load bearing cold-formed steel frame walls exposed to realistic design fire curves

Light gauge Steel Frame (LSF) walls are extensively used in the building industry due to the many advantages they provide over other wall systems. Although LSF walls have been used widely, fire design of LSF walls is based on approximate prescriptive methods based on limited fire tests. Also these fire tests were conducted using the standard fire curve (ISO 834-1, 1999 [1]) and the applicability of available design rules to realistic design fire curves has not been verified. This paper investigates the accuracy of existing fire design rules in the current cold-formed steel standards and the modifications proposed by previous researchers. Of these the recently developed design rules by Gunalan and Mahendran (2013) [2] based on Eurocode 3 Part 1.3 (EN 1993-1-3, 2006 [3]) and AS/NZS 4600 (Standards Australia (SA), 2005 [4]) for standard fire exposure (ISO 834-1, 1999 [1]) were investigated in detail to determine their applicability to predict the axial compression strengths and fire resistance ratings of LSF walls exposed to realistic design fire curves. This paper also presents the fire performance results of LSF walls exposed to a range of realistic fire curves obtained using a finite element analysis based parametric study. The results from the parametric study were used to develop a simplified design method based on the critical hot flange temperature to predict the fire resistance ratings of LSF walls exposed to realistic fire curves. Finally, the stud failure times (fire resistance rating) obtained from the fire design rules and the simplified design method were compared with parametric study results for LSF walls lined with single and double plasterboards, and externally insulated with rock fibres under realistic fire curves.

A New Methodology of Design Fires for Train Carriages Based on Exponential Curve Method

Design fires have great influences on the fire safety concepts and safety measures, and are the basis for any assessment and calculation in tunnel fire safety design. A new methodology of design fires for individual train carriages is proposed based on the exponential design fire curve method and state-of-the-art fire research. The three key parameters required for construction of a design fire are the maximum heat release rate, time to maximum heat release rate, and energy content. An overview of the full scale train carriage fire tests is given and the results show that the maximum heat release rate is in a range of 7 MW to 77 MW and the time to reach the maximum heat release rate varies from 7 min to 118 min. The method could be employed to one single train carriage or several carriages, and alternatively one carriage could be divided into several individual sections. To illustrate the use of the methodology, several engineering applications are presented, including design fires for a metro train carriage with a maximum heat release rate of 77 MW, a double-deck railway train carriage with a maximum heat release rate of 60 MW and a tram carriage with a maximum heat release rate of 28 MW. The main objective is to provide practicing engineers with a flexible and reliable methodology to make design fires for individual train carriages in performance-based tunnel fire safety design.