Full-scale Fire Tests Research Articles

Experimental and analytical investigation on fire resistance of glulam-concrete composite beams

The timber-concrete composite beam characterized by good mechanical behavior, low susceptibility to vibration and high sound insulation has a wide application in high-rise and long-span timber structures. However, the published study on the fire resistance of TCC beam is limited. In this research, one short-term failure test at ambient temperature and five full-scale fire tests were performed on the glulam-concrete composite beams. The influences of the load ratio, presence of timber board and fire-rated gypsum plasterboard on the temperature field and fire resistance were investigated in detail. The test results showed that the fire resistance of the composite beam was decreased with the increase of the load ratio. The composite beam with timber board interlayer outperformed the beam without the interlayer in terms of fire resistance. Moreover, the fire-rated gypsum plasterboard protection on the glulam beam could effectively improve the fire resistance of the composite beam. The finite element models of the composite beams were established to predict the temperature field of composite beams under fire. The average temperature values of concrete slabs under different fire times were obtained from numerical simulations. Considering the influence of high temperature on the glulam beam, concrete slab and shear connectors, the calculation methods of load carrying capacity and bending stiffness of the composite beam under fire were proposed.

Experimental analysis of cross-laminated timber rib panels at normal temperature and in fire

The results of an experimental programme on the structural behaviour, fire behaviour, and fire resistance of CLT rib panels are presented. The floor system consists of cross-laminated timber (CLT) plates rigidly bonded to glued-laminated timber ribs by means of screw-press gluing.The experimental programme comprised ultimate-load tests at normal temperature as reference tests and full-scale fire resistance tests on four cross-sections. In addition to the reference tests, shear tests of the glue line between CLT plate and glued-laminated timber rib were performed for analysis of the cross-sections’ composite action.The results of the reference tests show good agreement with results based on the simplified method according to EN 1995-1-1 [1] and its final draft of CLT design [2]. The importance of the glue line’s quality was confirmed. The fire resistance tests show results on the safe side compared to predictions of the fire behaviour according to EN 1995-1-2 [3] and its actual draft [4]. However, the fire resistance was underestimated due to conservative assumptions about the composite cross-section’s structural behaviour.The experimental programme addressed the fire behaviour and fire resistance of CLT rib panels currently not covered in standards. The project’s overall aim is the development of design rules in fire for EN 1995-1-2.

Fire performance of modular wall panels: Numerical analysis

The Modular Building System (MBS) is increasingly popular and promoted due to the inherent advantages over conventional construction. Fire performance of a building has become a crucial design consideration because of the recent detrimental fire accidents. However, for modular buildings, there has been less previous evidence of research on the fire performance. Investigations become necessary since double skin wall and floor modular panel systems are involved in MBS in contrast to conventional buildings. Therefore, this work investigates the fire performance of Light-gauge Steel Framed (LSF) modular wall panels with different configurations through numerical analyses. Heat transfer numerical models were developed and validated against the full-scale fire test results comparing the time–temperature response. The validated numerical models were subsequently extended to analyse the fire performance of conventional and modular LSF wall panels. This includes 16 modular wall configurations with single and double fire resistance plasterboard linings and three different insulations, namely rock wool, glass fibre and mineral wool. The structural fire resistance time was determined using the established Load Ratio (LR) vs critical Hot-Flange (HF) temperature correlation. The results demonstrated that there is no noticeable difference in the structural fire resistance time between the modular and the corresponding mapped conventional LSF wall configurations. However, modular wall panels experience enhanced insulation fire resistance up to 170% for single-lined plasterboards and up to 80% for double-lined plasterboard configurations. The analysis also yields that there is no significant influence of the choice of insulation material between rock-wool, glass-fibre and mineral-wool on structural fire resistance.

Experiment and numerical simulation of cable trench fire detection

In this paper, the full-scale cable fire test is carried out in the fire compartment of cable trench in standard substation in order to explore the influence of fire detector sensitivity. The point-type temperature detector, point-type smoke detector, cable-type temperature detector, and suction-type smoke detector are used to test the fire alarm sequence. The temperature field, combustible gas concentration, and fire alarm sequence of fire detector with different sensitivity are simulated by FDS. The results show that: The numerical simulation results are in good agreement with the experimental results. The lower the alarm threshold, the shorter the response time of fire detector. The sensitivity of suction-type smoke detector has great influences on the detection results.

Numerical study of LSF walls made of cold-formed steel hollow section studs in fire

Cold-formed steel square and rectangular hollow section (SHS/RHS) studs are often used to replace the conventional lipped channel section studs in light gauge steel frame (LSF) wall systems to meet the required high load demand. To ensure adequate structural fire resistance of SHS/RHS stud walls, four full-scale fire tests were previously completed under standard fire conditions. However, the full-scale fire tests are expensive and time-consuming, while the complex fire performance cannot be adequately explained through test observations and results alone. Hence, a numerical study was undertaken by developing simplified and sheathed stud finite element (FE) models of tested walls. This paper provides the details of the developed models of LSF walls made of SHS/RHS studs at both ambient and elevated temperatures and a comparison with experimental results. The validated models were used to highlight the advantage of using SHS/RHS studs in cavity insulated stud walls and further understand the factors that may affect the fire resistance of LSF walls, such as steel grade and stud depth. In addition to the simplified stud model, advanced modelling techniques were used to explore the effects of sheathing and localised plasterboard fall-off on the wall behaviour in fire. Overall, this paper presents a numerical study of SHS/RHS stud walls and the simplified stud model developed in this paper can be used to predict the fire performance of other SHS/RHS stud walls with similar wall configurations.

Fire resistance of external light gauge steel framed walls clad with autoclaved aerated concrete panels

This paper presents an investigation into the fire resistance of external light gauge steel framed (LSF) walls clad with autoclaved aerated concrete (AAC) panels exposed to fire on the external side. Past research has been limited to the fire resistance of internal LSF walls clad with gypsum plasterboard on both sides. A series of experimental studies including thermal material property tests, a full-scale (3 m × 3 m) ambient capacity test of LSF wall and full-scale standard fire tests of non-load bearing and load bearing LSF walls were conducted to investigate the fire resistance of external LSF walls clad with AAC panels. Finally, a small-scale (1.2 m × 1.2 m) fire test of a wall made of AAC panels was also conducted to investigate the performance of joints between AAC panels. AAC panels with very low thermal conductivity performed exceptionally well by keeping the temperatures low for 160 min achieving a fire resistance level (FRL) of 204 min in load bearing conditions and 240 min in non-load bearing conditions. Hence, LSF walls clad with AAC panels can be used when higher FRLs are required. Experimental studies such as these on the whole system enable a good understanding of the overall fire performance of external wall systems in terms of structural adequacy and integrity instead of focusing only on the cladding.

Study on critical length for simulation in tunnel fires

Reasonable simulation length is of great significance to improve the computational efficiency. However, few research about the critical length for simulation have been conducted. In this study, critical length for simulation in tunnel fires was investigated numerically and theoretically. Through analyzing the variation of smoke layer temperature and smoke mass flow rate under different tunnel length, a criterion for selecting critical length is presented. Effect of tunnel cross-section and heat release rate on the critical length for simulation will be clarified. The linear growth relationship between the nondimensionless critical length L* and nondimensionless heat release rate Q* was obtained. This model perform good agreement with the full-scale tunnel fire test values of predecessors.

A solution to the thermal problem of fire resistance of spun reinforced concrete columns

Introduction. Spun reinforced concrete columns are widely used in the present-day international construction practice. Known formulas, used to calculate temperatures of cross sections of reinforced concrete structures, needed to assess their fire resistance limit, are successfully applied to homogeneous structures that have solid sections. However, they are inapplicable to spun reinforced concrete columns due to their structural features. The purpose of this work is to develop a method for solving a thermal problem of spun reinforced concrete columns and adapt existing calculation formulas.Materials and methods. This work addresses the heating of spun reinforced concrete structures in case of fire. Ansys Workbench was employed to perform the computer simulation needed to study the influence of the characteristics of spun reinforced concrete columns on their heating. Results and discussion. In the course of the theoretical studies, the effect, produced by column cavities, the heterogeneity of spun concrete and thin walls of these structures on the heating of their cross sections was assessed with regard for the results of full-scale fire tests of spun reinforced concrete columns. Correction coefficients were obtained in order to take account of these factors. A regression equation was derived as a result of the simulation performed in the context of a full-scale factorial experiment involving coefficient khol, which takes into account the rising temperature of hollow reinforced concrete structures in comparison with solid ones. Khet heating acceleration coefficient is applicable to spun reinforced concrete structures due to the heterogeneity of concrete in the cross section. This coefficient represents a function of the wall thickness. Coefficient kth, which allows for the heating acceleration in the course of crack opening in thin-walled structures, varies in the range of 1.00…1.40. The concrete cracking temperature is 550 °C.Conclusion. A new method allows to solve the thermal problem of fire resistance of spun reinforced concrete columns. The engineering formula used to calculate the temperature in a cross-section was adapted. The results of computer-aided simulation and calculation of temperature values, performed using the adapted formula, show acceptable convergence with the experimental data.

Mechanical Properties of Spruce Wood Extracted from GLT Beams Loaded by Fire

Heating wood to high temperature changes either temporarily or permanently its physical properties. This issue is addressed in the present contribution by examining the effect of high temperature on residual mechanical properties of spruce wood, grounding on the results of full-scale fire tests performed on GLT beams. Given these tests, a computational model was developed to provide through-thickness temperature profiles allowing for the estimation of a charring depth on the one hand and on the other hand assigning a particular temperature to each specimen used subsequently in small-scale tensile tests. The measured Young’s moduli and tensile strengths were accompanied by the results from three-point bending test carried out on two groups of beams exposed to fire of a variable duration and differing in the width of the cross-section, b=100 mm (Group 1) and b=160 mm (Group 2). As expected, increasing the fire duration and reducing the initial beam cross-section reduces the residual bending strength. A negative impact of high temperature on residual strength has also been observed from simple tensile tests, although limited to a very narrow layer adjacent to the charring front not even exceeding a typically adopted value of the zero-strength layer d0=7 mm. On the contrary, the impact on stiffness is relatively mild supporting the thermal recovery property of wood.

Fire testing of austenitic stainless steel I-section beam–columns

With the increasing use of stainless steel elements in construction, the need for comprehensive rules to enable their efficient structural design is clear. To date, the fire behaviour of stainless steel I-section beam–columns has been the subject of relatively little research. In particular, there is an absence of experimental data. To address this gap in knowledge, full-scale anisothermal fire tests on six grade 1.4301 austenitic stainless steel I-section beam–columns have been carried out; the test procedure and results are reported herein. The test specimens were subjected to eccentric axial compression with two eccentricity values so as to achieve different combinations of axial compression and uniform minor axis bending. Complementary initial local and global geometric imperfection measurements, room temperature tensile coupon tests and room temperature beam–column tests were also carried out. Based on the obtained experimental results, together with additional numerical results from a previous study, the existing design rules in the European structural steel fire design standard EN 1993-1-2 and the new design method of Kucukler et al. (2021) for stainless steel beam–columns in fire, which will be incorporated into the next version of EN 1993-1-2, are assessed.

실화재 실험을 통한 소방장갑의 열보호 성능평가

The purpose of the present study was to evaluate thermal protective performance of firefighting gloves through a full-scale fire test and explore methods to improve the validity of the full-scale fire test. Four experimental conditions using one type of firefighting gloves and a hand/arm manikins were evaluated (wet/dry condition × palmar/dorsal side exposure) through an exposure protocol (30-s steady, 12-s flame exposure, and 120-s recovery). The results showed that the surface temperature during the flame exposure and recovery was higher for the wet condition than for the dry condition (p<.05). The predicted burn area was greater for the wet condition compared to the dry condition (p<.05). It seems that the water penetrated into the wet gloves, evaporated at high temperatures and was retained as overheated live steam in the air trapped inside the gloves, which posed a high risk of burns. Further, under all experimental conditions, the fingers were more vulnerable to flame exposure than the palm or back of the hand, which is attributable to the thin distribution of trapped air around fingers. During the full-scale fire test, continuous temperature increases were observed inside the gloves during the recovery phase even after ending the flame exposure, and it is assumed that the heat stored in the gloves took time to spread around. All of these results suggest that a whole product-level assessment is necessary and that material-level assessment by itself is insufficient. In addition, we confirmed the need to consider gloves in the wet condition, and to balance the heat protection and dexterity of the gloves.

Simulation of Indoor Fire Dynamics of Residential Buildings with Full-Scale Fire Test

Along with simulated firefighting training, the development of virtual training systems and associated content has recently drawn attention as an alternative method for advanced firefighting training. In particular, to develop virtual training content, it is important to understand the combustion characteristics of indoor combustible materials and appropriately simulate their behavior. In this study, seven types of building fires were selected. From these types, indoor combustible materials of residential buildings were analyzed, and combustion tests were performed for each of three types of combustible materials. Furthermore, three types of indoor spaces, determined according to the combination of indoor combustible materials they contained, were divided into full-scale compartments, and a full-scale fire test was performed using this setup. Finally, the heat release rate and smoke production release of individual combustible materials and the room test were measured over time, and a fire dynamics simulation (FDS) was performed. As a result, it was confirmed that an effective evaluation of the occurrence and spread of fire indoors in buildings is possible through full-scale fire tests and FDS simulations. It is expected that simulation can be used as firefighting training content in the future by applying indoor combustible data and implementing complex and various fire development conditions.

Prediction of temperature variation in FRP-wrapped RC columns exposed to fire using artificial neural networks

This paper presents a novel application of artificial neural networks (ANNs) for predicting complete temperature profiles with varying time for circular reinforced concrete (RC) columns exposed to fire. The application is valid for un-strengthened columns or columns strengthened with fibre reinforced polymers (FRP) and isolated with different types and thicknesses of insulation materials under varying fire exposure condition. In addition, prediction of the temperature variation with time for constituent materials of the column such as concrete, reinforcement steel and FRP sheets is conducted. To reach this end, extensive nonlinear finite element analysis was conducted using ANSYS software to build database of 1200 training samples with different column diameters, concrete cover thicknesses, thermal conductivity curves, specific heat curves, insulation types and thicknesses. The prediction results of ANN model is validated against published full-scale experimental studies which reveal good agreement between experimental and predicted results. The novelty of this technique is the ability of ANN model to predict rapidly and efficiently the temperature–time for any part of continent materials of reinforced concrete column many in case scenarios of parameters; this is especially useful in avoiding the time-consuming and costly full-scale experimental fire tests. Moreover, this study encourages designers to use FRP in design applications in spite of the threat of fire conditions, by utilizing ANN as backend calculation provider for software design tool with graphical user interface presented in this paper.

Thermal behaviour of unloaded concrete tunnel lining through an innovative large-scale tunnel fire experimental testing setup

A full-scale tunnel fire test requires extensive preparation of the fire source and an empirical design setup of the tunnel to reach 1200 °C of tunnel fire temperature. This paper shows comprehensive experimental research on the method of designing a large scale fire test setup for new unloaded concrete tunnel segments. The thermal and spalling behaviour of fire-resistant Patent- MY-163281 composition concrete (PMC) tunnel lining segments are compared to those of a current construction project coded SPC. The tests were conducted to follow the RABT time–temperature curve. Unloaded tunnel segments were considered to minimise the effects of mechanical loading on the spalling and failure behaviour. The results show that the test setup could replicate the RABT time–temperature curve with a nominal difference. The temperatures decreased gradually, with the increasing depth of concrete cover from the surface exposed to fire, with the PMC segments less than SPC’s. The PMC segments showed good concrete spalling resistance behaviour, but the SPC segments were severely spalled. The PMC tunnel lining showed better performance under tunnel fire compared to SPC lining with similar design strength.

Experimental Study on Fire Sources for Full-Scale Fire Testing of Simple Sprinkler Systems Installed in Multiplexes

Fires are accidents that can cause numerous human casualties in multiplexes. The simple sprinkler systems applied in South Korea employ sprinklers to protect people against residential fires, as specified by the National Fire Protection Association (NFPA) standard 13D. Therefore, it is necessary to evaluate the fire control performance of multiplexes, which are at a greater risk than residential facilities. This study aims to verify the fire control performance of simple sprinklers in multiplexes and to develop a fire source that can be used as a protocol for testing fire suppression methods. The fire source was evaluated by using a 3 MW large-scale calorimeter (ISO 13784). The proposed fire source for multiplexes was applied in various forms according to the application methods, with ignition sources including cotton wick, wood crib, and heptane, and then the fire tests were conducted.

Estimating the two-dimensional thermal environment generated by strong fire plumes in an urban utility tunnel

Although utility tunnels act as an innovative technique for the sustainable development of city’s utilities and limited underground space today, the fire issues in this type of tunnel should be carefully treated as they are different from traffic tunnel fire scenarios. In order to propose an easy-to-use two-dimensional (2D) temperature estimation methodology that is helpful to the designers, operators and firefighters, the temperature distributions and ceiling jet thickness (the vertical distance from the ceiling to where the temperature within the fire-induced smoke flow drops to half of its maximum at a certain location) were investigated with full-scale fire tests in a utility tunnel. The vertical temperature distributions were represented as a normalized single convex-concave profile. Self-similarity was confirmed and three types of similarity profiles were found. In order to correlate the inner boundary layer region and outer region of these ceiling jet flow profiles, a series of mathematical functions combining a power function and Gortler’s error function were employed. Furthermore, the ceiling jet thickness was found to vary as a power function with the longitudinal distance, rather than being a constant as previous research suggested. The vertical distribution model, the ceiling jet thickness model and the longitudinal temperature decay model were combined into a framework to empirically estimate the 2D thermal environment generated by strong fire plumes in utility tunnel’s fire protection engineering practice.

Fire tests of cold-formed steel walls made of hollow section studs

Light gauge steel frame (LSF) walls as primary load-bearing components have been increasingly used in the construction of cold-formed steel (CFS) buildings. Their fire safety has thus become an important consideration for designers. Currently, LSF walls made of lipped channel section (LCS) studs are commonly used in low-rise buildings, but with the expansion of CFS applications to mid-rise buildings, cold-formed steel square and rectangular hollow section (SHS/RHS) studs are being used to meet the higher load capacity demands. However, the fire resistance of LSF walls made of SHS/RHS studs has not been investigated yet, so their fire resistance levels (FRLs) are unknown, restricting their use in mid-rise buildings. Four full-scale load-bearing standard fire tests were therefore conducted to investigate the performance of cold-formed steel SHS/RHS stud walls exposed to fire. The test results showed that CFS SHS/RHS stud walls achieved a higher FRL due to the superior elevated temperature mechanical properties of CFS SHS/RHS, while the temperature development exhibited good similarity with uninsulated LCS stud walls of the same wall configuration. However, a different thermal behaviour was observed when SHS/RHS studs were used in cavity insulated walls, as the hollow cavity reduced the temperature difference between the stud hot and cold flanges. This eliminated the fire resistance reduction caused by thermal bowing deformations and provided an improved fire performance than cavity insulated LCS stud walls. This paper presents the details of the fire tests and the results.

Thermal Analysis Infrastructure in OpenSees for Fire and its Smart Application Interface Towards Natural Fire Modelling

Understanding the fire behaviour in buildings is fundamental and crucial to the practice of structural fire safety design. Traditionally, time-temperature curves associated with a burning rate developed from the “compartment fire framework” are most widely used by structural engineers and applied as a load to the structure. However, the adequacy of homogenous temperature distribution in fully developed fires was questioned by researchers after reviewing the existing fire test data, which suggested a localised burning nature of the fires in relatively large compartments. A groundbreaking travelling fire concept and travelling fire models were then proposed intending to provide an engineering description to this type of natural fire behaviour. The work in this paper was driven by such a trend and first summarises the modelling infrastructure in OpenSees to estimate the thermal response of structural members subjected to various scenario fires, followed by providing a smart application interface to capture the appropriate form of natural fire model through Python-OpenSees framework. The developed modelling infrastructure is validated against uniform and localised fire tests, which are also discussed regarding the smoke effect afterwards. Using the Python-OpenSees infrastructure, a real-scale localised fire test and the Malveira travelling fire test are modelled to demonstrate the modelling strategy. The work as preliminary attempts has shown the necessity of introducing additional variables when describing the natural fire impact, and this framework can be further improved in future by including more fire dynamics research and full-scale fire test input.

Development of a smoke prediction model using numerical simulations

Conducting a full-scale fire test is the best way to acquire information regarding smoke and fire conditions for the purpose of fire safety protection and prevention installation. However, a full-scale fire experiment is expensive, time consuming and unrepeatable due to the unstable nature of fire. The main goal of this study was to develop a quantitative tool to analyse the smoke temperature in a stairway by utilising a fire dynamic simulator software. A result of this study provides mathematical correlation that could predict temperatures in adjacent vertical shafts used as a stairway which is useful in performance based design. The smoke temperature predicted using the developed model compared with numerical data showed errors less than 30% were considered satisfactory and the equation considered acceptable for this study.

Efficiency of insulation layers in fire protection of FRP-confined RC columns-numerical study

This paper addresses the efficiency of thermal insulation layers applied to protect structural elements strengthened by fiber-reinforced polymers (FRP) in the case of fire event. The paper presents numerical modeling and nonlinear analysis of reinforced concrete (RC) columns externally strengthened by FRP and protected by thermal insulation layers when subjected to elevated temperature specified by standard fire tests, in order to predict their residual capacity and fire endurance. The adopted numerical approach uses commercial software includes heat transfer, variation of thermal and mechanical properties of concrete, steel reinforcement, FRP and insulation material with elevated temperature. The numerical results show good agreement with published results of full-scale fire tests. A parametric study was conducted to investigate the influence of several variables on the structural response and residual capacity of insulated FRP-confined columns loaded by service loads when exposed to fire. The residual capacity of FRP-confined RC column was affected by concrete grade and insulation material and was shown to improve substantially by increasing the concrete cover and insulation layer thickness. By increasing the VG insulation layer thickness 15, 32, 44, 57 mm, the loss in column capacity after 5 hours of fire was 30%, 13%, 7% and 5%, respectively. The obtained results demonstrate the validity of the presented approach for estimation of fire endurance and residual strength, as an alternative for fire testing, and for design of fire protection layers for FRP-confined RC columns.