Fire and Materials最新文献

This study investigates the combined thermal and mechanical response of pre-loaded woven carbon-epoxy U-channels subjected to radiant heating conditions similar to those experienced by aircraft structures in the event of a fire. A custom-built laboratory scale test rig was used to combine the mechanical loads and thermal boundary conditions. The main experimental aim was to measure failure times, failure modes, displacement and temperature distribution of the U-channels. The results show that the U-channels undergo multiple phases of decomposition when exposed to heat. These phases include physico-chemical changes such as bubble formation, visible charring, and epoxy resin pyrolysis. Additionally, the U-channels experience mechanical degradation through thermal-induced delamination and torsional deformation, causing the flange furthest from the heat source to buckle. The rate of decomposition and loss of load-bearing capacity are directly proportional to heat flux, with higher heat fluxes accelerating these processes. Analysis of displacement data reveals that higher heat fluxes correlate with lower displacement variability over time for U-channels under identical thermal conditions. Temperature measurements indicate that higher heat fluxes result in higher temperatures but lower temperature gradients, directly influencing failure times and modes. Consequently, higher temperatures lead to shorter failure times, while lower temperatures extend failure times. The findings from this study will provide valuable knowledge to inform optimised approaches, especially in the domain of aircraft structural fire safety.

This paper presents the results of a standard fire resistance test of a loaded steel beam in a horizontal furnace. The beam was tested in three configurations: (1) unprotected, (2) protected with a single 22 mm layer of oriented strand board, and (3) protected with a double layer of the same cladding. The study also describes the development of a model in Fire Dynamics Simulator to predict the thermal conditions in the furnace and to observe the temperature trends on the beam surface, on the cladding, and at various depths in the cladding. A comparison between calculated and measured temperatures showed good agreement for the unprotected beam. However, for the protected beams, the model underestimated temperatures after 15 and 30 min for the single-layer and double-layer protection, respectively. Several potential sources for the discrepancies are identified. The main reason lies probably in the model's inability to correctly account for the effect of gaps in the cladding joints. Future work will focus on improving the accuracy of the model by removing these identified limitations, with particular attention to the behavior of the cladding as a passive fire protection material.

With a drive for sustainable construction, various products are being introduced to promote recycling, but often their properties relation to behaviour in fire are not known. In this paper, the fire performance of crumb rubber and a plastic eco-aggregate, called RESIN8, were assessed. Various tests, including cone calorimeter, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC), were conducted. These are supplemented by numerical calculations and the Coats–Redfern kinetic model to quantify the thermal and fire properties of these materials. Cone calorimeter tests were conducted at 35 and 50 kW m⁻², while the critical heat flux (CHF) values were determined using a range of irradiance levels. Time to ignition (TTI), heat release rate (HRR), peak heat release rate (pHRR), and thermal fire hazard parameters were quantified. Both materials were classified under the high thermal fire hazard class. The peak thermal decomposition rates occurred at 365°C (single peak) for CR and at 435°C and 550°C (two peaks) for RESIN8. The calculated activation energy values were 66.7 kJ mol⁻¹ for crumb rubber and 55.1 and 43.9 kJ mol⁻¹ for RESIN8 in the first and second stages, respectively. These eco-aggregates could pose a significant thermal fire hazard, in the recycling facility during and after the recycling process, as well as when stored in bulk and when incorporated in large quantities in construction systems. Further investigation is crucial for understanding the effect of incorporating these eco-aggregates within masonry and concrete systems from a fire safety perspective.

In this paper, we investigate the plug-holing phenomenon under the influence of natural smoke venting in deeply buried tunnel shafts using a fire dynamics simulator based on a large eddy simulation model. Additionally, we discuss the effects of heat release rate and shaft height. The results indicate that the temperature distribution of the smoke upstream of the fire remains consistent when the height of the shaft does not exceed 20 m. Once the shaft height reaches 50 m, the temperature of the smoke upstream of the fire decreases with the increase in shaft height. Simultaneously, the smoke downstream of the fire can be completely discharged through the shaft. As the shaft height increases in the deeply buried tunnel, the degree of plug-holing increases, leading to reduced smoke evacuation efficiency. This phenomenon is caused by the horizontal inertia force and vertical thermal buoyancy of the smoke below the shaft. The critical plugging phenomenon occurs when Ri = 2.72, as determined through force analysis of the smoke. Subsequently, we analyze the mechanism by which shaft height and heat release rate influence plug hole height and establish a quantitative expression equation for plug-holing height.

The National Research Council Canada conducted two major fire resistance studies on floor assemblies over the past two decades. Despite the publication of the experimental results, there is a lack of suggested guidelines for design practitioners and gaps for future research. Thus, this paper comprehensively reviews the fire resistance results of 85 full-scale floor tests, suggests design guidelines, and identifies research gaps. These efforts aim to enhance the understanding and support the potential improvement of the fire performance of floor assemblies. The review of the results covers the impact of various design parameters on the fire resistance of floor assemblies, such as framing type and spacing, insulation type, subfloor configuration, resilient channel spacing, number of gypsum board layers, and screw spacing from the board edge. Although the interaction of these factors is complex, some of them play significant roles in determining the overall fire resistance of floor assemblies. For instance, rock and cellulose insulation outperformed glass fibre, a wider resilient channel spacing lowered fire resistance, whilst an increased distance of screws from the board edge improved the fire resistance. More importantly, detailed explanations are provided for the influences these parameters exert on fire resistance. Following this detailed examination of the results, design guidelines are provided for practitioners' consideration. A comparison is made between the experimental results and predictions from the component additive methods in the Canadian and Euro Codes, demonstrating that both methods yield conservative results. Finally, this paper concludes by identifying research gaps and providing recommendations for future investigations, including the necessity of experimental studies on floor assemblies with new design configurations and the promising role of machine learning in fire resistance evaluation.

During the recycling process, waste plastic undergoes various processes that change its geometry. The thermal properties and fire behaviour of plastic in different geometries has not been widely studied. This paper aims to determine critical thermal properties of plastic pellets made of recycled plastic. For this paper, cone calorimeter tests of various volumes of recycled plastic pellets of low- and high-density polyethylene and polypropylene were conducted. During these tests, the heat release rate (HRR), mass loss rate and time-to-ignition were measured, thereafter the heat of combustion (HOC) was calculated. A calibration of suitable time-to-ignition equations is carried out. The average HRR is between 353 and 581 kW/m² with an external heat flux of 50 kW/m². The measured time-to-ignition values ranged between 27 s at 50 kW/m² and just more than 90 s at 25 kW/m². Values obtained analytically from the thermally thin time-to-ignition equations for these materials describe ignition well, which appears to be due to the particulate nature of the samples. The HOC (40–41 MJ/kg) shows good agreement with the HOC for virgin plastic found in literature. These properties can be used as a basis for material characterisation, and further testing will be done before using this as simulation inputs to determine how bulk stored plastic pellets will behave in the event of a fire.

Low-temperature chemical oxidation is the major driver of self-heating during storage of wood pellets and its kinetics is essential to describe the heat evolution. In the present work, isothermal microcalorimetry was used to characterize heat generation behavior of three types of wood pellets (pine, fir, and redwood pellets) at 30–70°C. The obtained data were employed to derive the kinetics of low-temperature oxidation by the peak power, iso-conversional method, and non-steady analysis. The consistency and applicability of the kinetics derived by the three methods were evaluated. Kinetic parameters determined by the peak power method were observed to match those from the iso-conversional method at lower conversions of the oxidation for heat generation. The kinetics derived by the iso-conversional method indicated the oxidation reactivity generally decreasing and activation energy increasing with the conversion because of O₂ consumption and reaction mechanism changing. With the impact of O₂ consumption considered separately, the kinetics from the non-steady analysis is capable of describing the evolution of heat power with the conversion and also consistent with that from the peak power method in describing intrinsic reactivity of pellet materials. The kinetics from the peak power and iso-conversional methods lump the impact of O₂ concentration with the reaction reactivity, suggesting their applications requiring additional models for connecting with O₂ consumption.

Simulating fire and evacuation scenarios is crucial for engineers to assess building safety during fire incidents. Accurate simulations require data on occupants' behaviors, particularly during the pre-evacuation phase as these decisions significantly impact evacuation duration. Gathering comprehensive data from diverse regions while considering cultural and regional variations is necessary to understand how occupants' behavior is influenced. Thus, this study focuses on examining the behavior of Malaysian hotel staff during unannounced fire drill to gain insights into factors affecting their behavior during pre-evacuation stage, such as fire experience, fire alarm, drill participation, fire training, and awareness. The study categorizes the actions performed by the hotel staff into sequences and analyses them based on influencing factors. The findings indicate that instead of immediately evacuating in response to emergency notification, the hotel staff engage in various actions. Most staff members initially investigate or ignore the emergency, resulting in longer pre-evacuation times. Moreover, the results suggest that previous drill participation and high awareness levels contribute to shorter pre-evacuation times. Conversely, previous fire experience, fire training, and fire alarm familiarity have no effect on pre-evacuation time.